Merge 3.2.x branch into master (#2648)

* Down-integrate internal changes to github.

* Update conformance test failure list.

* Explicitly import used class in nano test to avoid random test fail.

* Update _GNUC_VER to use the correct implementation of atomic operation
on Mac.

* maps_test.js: check whether Symbol is defined before using it (#2524)

Symbol is not yet available on older versions of Node.js and so this
test fails with them. This change just directly checks whether Symbol is
available before we try to use it.

* Added well_known_types_embed.cc to CLEANFILES so that it gets cleaned up

* Updated Makefile.am to fix out-of-tree builds

* Added Bazel genrule for generating well_known_types_embed.cc

In pull request #2517 I made this change for the CMake and autotools
builds but forgot to do it for the Bazel build.

* Update _GNUC_VER to use the correct implementation of atomic operation on Mac.

* Add new js file in extra dist.

* Bump version number to 3.2.0

* Fixed issue with autoloading - Invalid paths (#2538)

* PHP fix int64 decoding (#2516)

* fix int64 decoding

* fix int64 decoding + tests

* Fix int64 decoding on 32-bit machines.

* Fix warning in compiler/js/embed.cc

embed.cc: In function ‘std::string CEscape(const string&)’:
embed.cc:51:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < str.size(); ++i) {
                                ^

* Fix include in auto-generated well_known_types_embed.cc

Restore include style fix (e3da722) that has been trampled by
auto-generation of well_known_types_embed.cc

* Fixed cross compilations with the Autotools build

Pull request #2517 caused cross compilations to start failing, because
the js_embed binary was being built to run on the target platform
instead of on the build machine. This change updates the Autotools build
to use the AX_PROG_CXX_FOR_BUILD macro to find a suitable compiler for
the build machine and always use that when building js_embed.

* Minor fix for autocreated object repeated fields and maps.

- If setting/clearing a repeated field/map that was objects, check the class
  before checking the autocreator.
- Just to be paranoid, don’t mutate within copy/mutableCopy for the autocreated
  classes to ensure there is less chance of issues if someone does something
  really crazy threading wise.
- Some more tests for the internal AutocreatedArray/AutocreatedDictionary
  classes to ensure things are working as expected.
- Add Xcode 8.2 to the full_mac_build.sh supported list.

* Fix generation of extending nested messages in JavaScript (#2439)

* Fix generation of extending nested messages in JavaScript

* Added missing test8.proto to build

* Fix generated code when there is no namespace but there is enum definition.

* Decoding unknown field should succeed.

* Add embed.cc in src/Makefile.am to fix dist check.

* Fixed "make distcheck" for the Autotools build

To make the test pass I needed to fix out-of-tree builds and update
EXTRA_DIST and CLEANFILES.

* Remove redundent embed.cc from src/Makefile.am

* Update version number to 3.2.0-rc.1 (#2578)

* Change protoc-artifacts version to 3.2.0-rc.1

* Update version number to 3.2.0rc2

* Update change logs for 3.2.0 release.

* Update php README

* Update upb, fixes some bugs (including a hash table problem). (#2611)

* Update upb, fixes some bugs (including a hash table problem).

* Ruby: added a test for the previous hash table corruption.

Verified that this triggers the bug in the currently released
version.

* Ruby: bugfix for SEGV.

* Ruby: removed old code for dup'ing defs.

* Reverting deployment target to 7.0 (#2618)

The Protobuf library doesn’t require the 7.1 deployment target so
reverting it back to 7.0

* Fix typo that breaks builds on big-endian (#2632)

* Bump version number to 3.2.0

4 files changed, 2787 insertions, 1365 deletions

diff --git a/ruby/ext/google/protobuf_c/defs.c b/ruby/ext/google/protobuf_c/defs.c
index 7e93bafb..845c0225 100644
--- a/ruby/ext/google/protobuf_c/defs.c
+++ b/ruby/ext/google/protobuf_c/defs.c
@@ -101,7 +101,7 @@ void DescriptorPool_mark(void* _self) {
 
 void DescriptorPool_free(void* _self) {
   DescriptorPool* self = _self;
-  upb_symtab_unref(self->symtab, &self->symtab);
+  upb_symtab_free(self->symtab);
   xfree(self);
 }
 
@@ -113,7 +113,7 @@ void DescriptorPool_free(void* _self) {
  */
 VALUE DescriptorPool_alloc(VALUE klass) {
   DescriptorPool* self = ALLOC(DescriptorPool);
-  self->symtab = upb_symtab_new(&self->symtab);
+  self->symtab = upb_symtab_new();
   return TypedData_Wrap_Struct(klass, &_DescriptorPool_type, self);
 }
 
diff --git a/ruby/ext/google/protobuf_c/encode_decode.c b/ruby/ext/google/protobuf_c/encode_decode.c
index 08c72bcc..d86a1145 100644
--- a/ruby/ext/google/protobuf_c/encode_decode.c
+++ b/ruby/ext/google/protobuf_c/encode_decode.c
@@ -514,7 +514,7 @@ static void add_handlers_for_singular_field(upb_handlers *h,
     case UPB_TYPE_INT64:
     case UPB_TYPE_UINT64:
     case UPB_TYPE_DOUBLE:
-      upb_shim_set(h, f, offset, -1);
+      upb_msg_setscalarhandler(h, f, offset, -1);
       break;
     case UPB_TYPE_STRING:
     case UPB_TYPE_BYTES: {
@@ -925,7 +925,7 @@ static void putmsg(VALUE msg, const Descriptor* desc,
 static upb_selector_t getsel(const upb_fielddef *f, upb_handlertype_t type) {
   upb_selector_t ret;
   bool ok = upb_handlers_getselector(f, type, &ret);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return ret;
 }
 
@@ -939,9 +939,9 @@ static void putstr(VALUE str, const upb_fielddef *f, upb_sink *sink) {
   // We should be guaranteed that the string has the correct encoding because
   // we ensured this at assignment time and then froze the string.
   if (upb_fielddef_type(f) == UPB_TYPE_STRING) {
-    assert(rb_enc_from_index(ENCODING_GET(value)) == kRubyStringUtf8Encoding);
+    assert(rb_enc_from_index(ENCODING_GET(str)) == kRubyStringUtf8Encoding);
   } else {
-    assert(rb_enc_from_index(ENCODING_GET(value)) == kRubyString8bitEncoding);
+    assert(rb_enc_from_index(ENCODING_GET(str)) == kRubyString8bitEncoding);
   }
 
   upb_sink_startstr(sink, getsel(f, UPB_HANDLER_STARTSTR), RSTRING_LEN(str),
diff --git a/ruby/ext/google/protobuf_c/upb.c b/ruby/ext/google/protobuf_c/upb.c
index 544ebc04..e0c56f8e 100644
--- a/ruby/ext/google/protobuf_c/upb.c
+++ b/ruby/ext/google/protobuf_c/upb.c
@@ -103,7 +103,7 @@ const char *upb_def_name(const upb_def *d) {
 }
 
 bool upb_def_setfullname(upb_def *def, const char *fullname, upb_status *s) {
-  assert(!upb_def_isfrozen(def));
+  UPB_ASSERT(!upb_def_isfrozen(def));
   if (!upb_isident(fullname, strlen(fullname), true, s)) {
     return false;
   }
@@ -121,21 +121,6 @@ bool upb_def_setfullname(upb_def *def, const char *fullname, upb_status *s) {
 
 const upb_filedef *upb_def_file(const upb_def *d) { return d->file; }
 
-upb_def *upb_def_dup(const upb_def *def, const void *o) {
-  switch (def->type) {
-    case UPB_DEF_MSG:
-      return upb_msgdef_upcast_mutable(
-          upb_msgdef_dup(upb_downcast_msgdef(def), o));
-    case UPB_DEF_FIELD:
-      return upb_fielddef_upcast_mutable(
-          upb_fielddef_dup(upb_downcast_fielddef(def), o));
-    case UPB_DEF_ENUM:
-      return upb_enumdef_upcast_mutable(
-          upb_enumdef_dup(upb_downcast_enumdef(def), o));
-    default: assert(false); return NULL;
-  }
-}
-
 static bool upb_def_init(upb_def *def, upb_deftype_t type,
                          const struct upb_refcounted_vtbl *vtbl,
                          const void *owner) {
@@ -203,14 +188,14 @@ static bool upb_validate_field(upb_fielddef *f, upb_status *s) {
     bool has_default_number = upb_fielddef_enumhasdefaultint32(f);
 
     /* Previously verified by upb_validate_enumdef(). */
-    assert(upb_enumdef_numvals(upb_fielddef_enumsubdef(f)) > 0);
+    UPB_ASSERT(upb_enumdef_numvals(upb_fielddef_enumsubdef(f)) > 0);
 
     /* We've already validated that we have an associated enumdef and that it
      * has at least one member, so at least one of these should be true.
      * Because if the user didn't set anything, we'll pick up the enum's
      * default, but if the user *did* set something we should at least pick up
      * the one they set (int32 or string). */
-    assert(has_default_name || has_default_number);
+    UPB_ASSERT(has_default_name || has_default_number);
 
     if (!has_default_name) {
       upb_status_seterrf(s,
@@ -266,7 +251,7 @@ static bool upb_validate_enumdef(const upb_enumdef *e, upb_status *s) {
 uint32_t field_rank(const upb_fielddef *f) {
   uint32_t ret = upb_fielddef_number(f);
   const uint32_t high_bit = 1 << 30;
-  assert(ret < high_bit);
+  UPB_ASSERT(ret < high_bit);
   if (!upb_fielddef_issubmsg(f))
     ret |= high_bit;
   return ret;
@@ -282,6 +267,7 @@ static bool assign_msg_indices(upb_msgdef *m, upb_status *s) {
   /* Sort fields.  upb internally relies on UPB_TYPE_MESSAGE fields having the
    * lowest indexes, but we do not publicly guarantee this. */
   upb_msg_field_iter j;
+  upb_msg_oneof_iter k;
   int i;
   uint32_t selector;
   int n = upb_msgdef_numfields(m);
@@ -304,7 +290,7 @@ static bool assign_msg_indices(upb_msgdef *m, upb_status *s) {
       !upb_msg_field_done(&j);
       upb_msg_field_next(&j), i++) {
     upb_fielddef *f = upb_msg_iter_field(&j);
-    assert(f->msg.def == m);
+    UPB_ASSERT(f->msg.def == m);
     if (!upb_validate_field(f, s)) {
       upb_gfree(fields);
       return false;
@@ -366,6 +352,13 @@ static bool assign_msg_indices(upb_msgdef *m, upb_status *s) {
 #undef TRY
 #endif
 
+  for(upb_msg_oneof_begin(&k, m), i = 0;
+      !upb_msg_oneof_done(&k);
+      upb_msg_oneof_next(&k), i++) {
+    upb_oneofdef *o = upb_msg_iter_oneof(&k);
+    o->index = i;
+  }
+
   upb_gfree(fields);
   return true;
 }
@@ -417,7 +410,7 @@ err:
     upb_def *def = defs[i];
     def->came_from_user = false;
   }
-  assert(!(s && upb_ok(s)));
+  UPB_ASSERT(!(s && upb_ok(s)));
   return false;
 }
 
@@ -438,7 +431,16 @@ bool upb_def_freeze(upb_def *const* defs, size_t n, upb_status *s) {
 
 /* upb_enumdef ****************************************************************/
 
-static void upb_enumdef_free(upb_refcounted *r) {
+static void visitenum(const upb_refcounted *r, upb_refcounted_visit *visit,
+                      void *closure) {
+  const upb_enumdef *e = (const upb_enumdef*)r;
+  const upb_def *def = upb_enumdef_upcast(e);
+  if (upb_def_file(def)) {
+    visit(r, upb_filedef_upcast(upb_def_file(def)), closure);
+  }
+}
+
+static void freeenum(upb_refcounted *r) {
   upb_enumdef *e = (upb_enumdef*)r;
   upb_inttable_iter i;
   upb_inttable_begin(&i, &e->iton);
@@ -452,7 +454,7 @@ static void upb_enumdef_free(upb_refcounted *r) {
   upb_gfree(e);
 }
 
-const struct upb_refcounted_vtbl upb_enumdef_vtbl = {NULL, &upb_enumdef_free};
+const struct upb_refcounted_vtbl upb_enumdef_vtbl = {&visitenum, &freeenum};
 
 upb_enumdef *upb_enumdef_new(const void *owner) {
   upb_enumdef *e = upb_gmalloc(sizeof(*e));
@@ -474,21 +476,6 @@ err2:
   return NULL;
 }
 
-upb_enumdef *upb_enumdef_dup(const upb_enumdef *e, const void *owner) {
-  upb_enum_iter i;
-  upb_enumdef *new_e = upb_enumdef_new(owner);
-  if (!new_e) return NULL;
-  for(upb_enum_begin(&i, e); !upb_enum_done(&i); upb_enum_next(&i)) {
-    bool success = upb_enumdef_addval(
-        new_e, upb_enum_iter_name(&i),upb_enum_iter_number(&i), NULL);
-    if (!success) {
-      upb_enumdef_unref(new_e, owner);
-      return NULL;
-    }
-  }
-  return new_e;
-}
-
 bool upb_enumdef_freeze(upb_enumdef *e, upb_status *status) {
   upb_def *d = upb_enumdef_upcast_mutable(e);
   return upb_def_freeze(&d, 1, status);
@@ -536,19 +523,19 @@ bool upb_enumdef_addval(upb_enumdef *e, const char *name, int32_t num,
 
   if (upb_enumdef_numvals(e) == 1) {
     bool ok = upb_enumdef_setdefault(e, num, NULL);
-    UPB_ASSERT_VAR(ok, ok);
+    UPB_ASSERT(ok);
   }
 
   return true;
 }
 
 int32_t upb_enumdef_default(const upb_enumdef *e) {
-  assert(upb_enumdef_iton(e, e->defaultval));
+  UPB_ASSERT(upb_enumdef_iton(e, e->defaultval));
   return e->defaultval;
 }
 
 bool upb_enumdef_setdefault(upb_enumdef *e, int32_t val, upb_status *s) {
-  assert(!upb_enumdef_isfrozen(e));
+  UPB_ASSERT(!upb_enumdef_isfrozen(e));
   if (!upb_enumdef_iton(e, val)) {
     upb_status_seterrf(s, "number '%d' is not in the enum.", val);
     return false;
@@ -610,6 +597,7 @@ const char *upb_fielddef_fullname(const upb_fielddef *e) {
 static void visitfield(const upb_refcounted *r, upb_refcounted_visit *visit,
                        void *closure) {
   const upb_fielddef *f = (const upb_fielddef*)r;
+  const upb_def *def = upb_fielddef_upcast(f);
   if (upb_fielddef_containingtype(f)) {
     visit(r, upb_msgdef_upcast2(upb_fielddef_containingtype(f)), closure);
   }
@@ -619,6 +607,9 @@ static void visitfield(const upb_refcounted *r, upb_refcounted_visit *visit,
   if (upb_fielddef_subdef(f)) {
     visit(r, upb_def_upcast(upb_fielddef_subdef(f)), closure);
   }
+  if (upb_def_file(def)) {
+    visit(r, upb_filedef_upcast(upb_def_file(def)), closure);
+  }
 }
 
 static void freefield(upb_refcounted *r) {
@@ -632,7 +623,7 @@ static void freefield(upb_refcounted *r) {
 
 static const char *enumdefaultstr(const upb_fielddef *f) {
   const upb_enumdef *e;
-  assert(f->type_is_set_ && f->type_ == UPB_TYPE_ENUM);
+  UPB_ASSERT(f->type_is_set_ && f->type_ == UPB_TYPE_ENUM);
   e = upb_fielddef_enumsubdef(f);
   if (f->default_is_string && f->defaultval.bytes) {
     /* Default was explicitly set as a string. */
@@ -649,7 +640,7 @@ static const char *enumdefaultstr(const upb_fielddef *f) {
       /* Default is completely unset; pull enumdef default. */
       if (upb_enumdef_numvals(e) > 0) {
         const char *name = upb_enumdef_iton(e, upb_enumdef_default(e));
-        assert(name);
+        UPB_ASSERT(name);
         return name;
       }
     }
@@ -659,7 +650,7 @@ static const char *enumdefaultstr(const upb_fielddef *f) {
 
 static bool enumdefaultint32(const upb_fielddef *f, int32_t *val) {
   const upb_enumdef *e;
-  assert(f->type_is_set_ && f->type_ == UPB_TYPE_ENUM);
+  UPB_ASSERT(f->type_is_set_ && f->type_ == UPB_TYPE_ENUM);
   e = upb_fielddef_enumsubdef(f);
   if (!f->default_is_string) {
     /* Default was explicitly set as an integer. */
@@ -719,7 +710,8 @@ upb_fielddef *upb_fielddef_new(const void *o) {
   return f;
 }
 
-upb_fielddef *upb_fielddef_dup(const upb_fielddef *f, const void *owner) {
+static upb_fielddef *upb_fielddef_dup(const upb_fielddef *f,
+                                      const void *owner) {
   const char *srcname;
   upb_fielddef *newf = upb_fielddef_new(owner);
   if (!newf) return NULL;
@@ -760,7 +752,7 @@ bool upb_fielddef_typeisset(const upb_fielddef *f) {
 }
 
 upb_fieldtype_t upb_fielddef_type(const upb_fielddef *f) {
-  assert(f->type_is_set_);
+  UPB_ASSERT(f->type_is_set_);
   return f->type_;
 }
 
@@ -862,7 +854,7 @@ static void release_containingtype(upb_fielddef *f) {
 bool upb_fielddef_setcontainingtypename(upb_fielddef *f, const char *name,
                                         upb_status *s) {
   char *name_copy;
-  assert(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
   if (upb_fielddef_containingtype(f)) {
     upb_status_seterrmsg(s, "field has already been added to a message.");
     return false;
@@ -893,7 +885,7 @@ bool upb_fielddef_setname(upb_fielddef *f, const char *name, upb_status *s) {
 static void chkdefaulttype(const upb_fielddef *f, upb_fieldtype_t type) {
   UPB_UNUSED(f);
   UPB_UNUSED(type);
-  assert(f->type_is_set_ && upb_fielddef_type(f) == type);
+  UPB_ASSERT(f->type_is_set_ && upb_fielddef_type(f) == type);
 }
 
 int64_t upb_fielddef_defaultint64(const upb_fielddef *f) {
@@ -905,7 +897,7 @@ int32_t upb_fielddef_defaultint32(const upb_fielddef *f) {
   if (f->type_is_set_ && upb_fielddef_type(f) == UPB_TYPE_ENUM) {
     int32_t val;
     bool ok = enumdefaultint32(f, &val);
-    UPB_ASSERT_VAR(ok, ok);
+    UPB_ASSERT(ok);
     return val;
   } else {
     chkdefaulttype(f, UPB_TYPE_INT32);
@@ -939,14 +931,14 @@ double upb_fielddef_defaultdouble(const upb_fielddef *f) {
 }
 
 const char *upb_fielddef_defaultstr(const upb_fielddef *f, size_t *len) {
-  assert(f->type_is_set_);
-  assert(upb_fielddef_type(f) == UPB_TYPE_STRING ||
+  UPB_ASSERT(f->type_is_set_);
+  UPB_ASSERT(upb_fielddef_type(f) == UPB_TYPE_STRING ||
          upb_fielddef_type(f) == UPB_TYPE_BYTES ||
          upb_fielddef_type(f) == UPB_TYPE_ENUM);
 
   if (upb_fielddef_type(f) == UPB_TYPE_ENUM) {
     const char *ret = enumdefaultstr(f);
-    assert(ret);
+    UPB_ASSERT(ret);
     /* Enum defaults can't have embedded NULLs. */
     if (len) *len = strlen(ret);
     return ret;
@@ -1028,8 +1020,8 @@ bool upb_fielddef_setnumber(upb_fielddef *f, uint32_t number, upb_status *s) {
 }
 
 void upb_fielddef_settype(upb_fielddef *f, upb_fieldtype_t type) {
-  assert(!upb_fielddef_isfrozen(f));
-  assert(upb_fielddef_checktype(type));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(upb_fielddef_checktype(type));
   upb_fielddef_uninit_default(f);
   f->type_ = type;
   f->type_is_set_ = true;
@@ -1037,7 +1029,7 @@ void upb_fielddef_settype(upb_fielddef *f, upb_fieldtype_t type) {
 }
 
 void upb_fielddef_setdescriptortype(upb_fielddef *f, int type) {
-  assert(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
   switch (type) {
     case UPB_DESCRIPTOR_TYPE_DOUBLE:
       upb_fielddef_settype(f, UPB_TYPE_DOUBLE);
@@ -1079,7 +1071,7 @@ void upb_fielddef_setdescriptortype(upb_fielddef *f, int type) {
     case UPB_DESCRIPTOR_TYPE_ENUM:
       upb_fielddef_settype(f, UPB_TYPE_ENUM);
       break;
-    default: assert(false);
+    default: UPB_ASSERT(false);
   }
 
   if (type == UPB_DESCRIPTOR_TYPE_FIXED64 ||
@@ -1137,34 +1129,34 @@ upb_descriptortype_t upb_fielddef_descriptortype(const upb_fielddef *f) {
 }
 
 void upb_fielddef_setisextension(upb_fielddef *f, bool is_extension) {
-  assert(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
   f->is_extension_ = is_extension;
 }
 
 void upb_fielddef_setlazy(upb_fielddef *f, bool lazy) {
-  assert(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
   f->lazy_ = lazy;
 }
 
 void upb_fielddef_setpacked(upb_fielddef *f, bool packed) {
-  assert(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
   f->packed_ = packed;
 }
 
 void upb_fielddef_setlabel(upb_fielddef *f, upb_label_t label) {
-  assert(!upb_fielddef_isfrozen(f));
-  assert(upb_fielddef_checklabel(label));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(upb_fielddef_checklabel(label));
   f->label_ = label;
 }
 
 void upb_fielddef_setintfmt(upb_fielddef *f, upb_intfmt_t fmt) {
-  assert(!upb_fielddef_isfrozen(f));
-  assert(upb_fielddef_checkintfmt(fmt));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(upb_fielddef_checkintfmt(fmt));
   f->intfmt = fmt;
 }
 
 void upb_fielddef_settagdelim(upb_fielddef *f, bool tag_delim) {
-  assert(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
   f->tagdelim = tag_delim;
   f->tagdelim = tag_delim;
 }
@@ -1172,12 +1164,12 @@ void upb_fielddef_settagdelim(upb_fielddef *f, bool tag_delim) {
 static bool checksetdefault(upb_fielddef *f, upb_fieldtype_t type) {
   if (!f->type_is_set_ || upb_fielddef_isfrozen(f) ||
       upb_fielddef_type(f) != type) {
-    assert(false);
+    UPB_ASSERT(false);
     return false;
   }
   if (f->default_is_string) {
     str_t *s = f->defaultval.bytes;
-    assert(s || type == UPB_TYPE_ENUM);
+    UPB_ASSERT(s || type == UPB_TYPE_ENUM);
     if (s) freestr(s);
   }
   f->default_is_string = false;
@@ -1225,16 +1217,16 @@ void upb_fielddef_setdefaultdouble(upb_fielddef *f, double value) {
 bool upb_fielddef_setdefaultstr(upb_fielddef *f, const void *str, size_t len,
                                 upb_status *s) {
   str_t *str2;
-  assert(upb_fielddef_isstring(f) || f->type_ == UPB_TYPE_ENUM);
+  UPB_ASSERT(upb_fielddef_isstring(f) || f->type_ == UPB_TYPE_ENUM);
   if (f->type_ == UPB_TYPE_ENUM && !upb_isident(str, len, false, s))
     return false;
 
   if (f->default_is_string) {
     str_t *s = f->defaultval.bytes;
-    assert(s || f->type_ == UPB_TYPE_ENUM);
+    UPB_ASSERT(s || f->type_ == UPB_TYPE_ENUM);
     if (s) freestr(s);
   } else {
-    assert(f->type_ == UPB_TYPE_ENUM);
+    UPB_ASSERT(f->type_ == UPB_TYPE_ENUM);
   }
 
   str2 = newstr(str, len);
@@ -1245,18 +1237,18 @@ bool upb_fielddef_setdefaultstr(upb_fielddef *f, const void *str, size_t len,
 
 void upb_fielddef_setdefaultcstr(upb_fielddef *f, const char *str,
                                  upb_status *s) {
-  assert(f->type_is_set_);
+  UPB_ASSERT(f->type_is_set_);
   upb_fielddef_setdefaultstr(f, str, str ? strlen(str) : 0, s);
 }
 
 bool upb_fielddef_enumhasdefaultint32(const upb_fielddef *f) {
   int32_t val;
-  assert(f->type_is_set_ && f->type_ == UPB_TYPE_ENUM);
+  UPB_ASSERT(f->type_is_set_ && f->type_ == UPB_TYPE_ENUM);
   return enumdefaultint32(f, &val);
 }
 
 bool upb_fielddef_enumhasdefaultstr(const upb_fielddef *f) {
-  assert(f->type_is_set_ && f->type_ == UPB_TYPE_ENUM);
+  UPB_ASSERT(f->type_is_set_ && f->type_ == UPB_TYPE_ENUM);
   return enumdefaultstr(f) != NULL;
 }
 
@@ -1286,8 +1278,8 @@ static void release_subdef(upb_fielddef *f) {
 
 bool upb_fielddef_setsubdef(upb_fielddef *f, const upb_def *subdef,
                             upb_status *s) {
-  assert(!upb_fielddef_isfrozen(f));
-  assert(upb_fielddef_hassubdef(f));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(upb_fielddef_hassubdef(f));
   if (subdef && !upb_subdef_typecheck(f, subdef, s)) return false;
   release_subdef(f);
   f->sub.def = subdef;
@@ -1309,7 +1301,7 @@ bool upb_fielddef_setenumsubdef(upb_fielddef *f, const upb_enumdef *subdef,
 bool upb_fielddef_setsubdefname(upb_fielddef *f, const char *name,
                                 upb_status *s) {
   char *name_copy;
-  assert(!upb_fielddef_isfrozen(f));
+  UPB_ASSERT(!upb_fielddef_isfrozen(f));
   if (!upb_fielddef_hassubdef(f)) {
     upb_status_seterrmsg(s, "field type does not accept a subdef");
     return false;
@@ -1383,6 +1375,7 @@ static void visitmsg(const upb_refcounted *r, upb_refcounted_visit *visit,
                      void *closure) {
   upb_msg_oneof_iter o;
   const upb_msgdef *m = (const upb_msgdef*)r;
+  const upb_def *def = upb_msgdef_upcast(m);
   upb_msg_field_iter i;
   for(upb_msg_field_begin(&i, m);
       !upb_msg_field_done(&i);
@@ -1396,6 +1389,9 @@ static void visitmsg(const upb_refcounted *r, upb_refcounted_visit *visit,
     upb_oneofdef *f = upb_msg_iter_oneof(&o);
     visit(r, upb_oneofdef_upcast(f), closure);
   }
+  if (upb_def_file(def)) {
+    visit(r, upb_filedef_upcast(upb_def_file(def)), closure);
+  }
 }
 
 static void freemsg(upb_refcounted *r) {
@@ -1430,7 +1426,9 @@ err2:
   return NULL;
 }
 
-upb_msgdef *upb_msgdef_dup(const upb_msgdef *m, const void *owner) {
+static upb_oneofdef *upb_oneofdef_dup(const upb_oneofdef *o, const void *owner);
+
+static upb_msgdef *upb_msgdef_dup(const upb_msgdef *m, const void *owner) {
   bool ok;
   upb_msg_field_iter i;
   upb_msg_oneof_iter o;
@@ -1442,7 +1440,7 @@ upb_msgdef *upb_msgdef_dup(const upb_msgdef *m, const void *owner) {
                            NULL);
   newm->map_entry = m->map_entry;
   newm->syntax = m->syntax;
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   for(upb_msg_field_begin(&i, m);
       !upb_msg_field_done(&i);
       upb_msg_field_next(&i)) {
@@ -1544,6 +1542,7 @@ bool upb_msgdef_addfield(upb_msgdef *m, upb_fielddef *f, const void *ref_donor,
    * This method is idempotent. Check if |f| is already part of this msgdef and
    * return immediately if so. */
   if (upb_fielddef_containingtype(f) == m) {
+    if (ref_donor) upb_fielddef_unref(f, ref_donor);
     return true;
   }
 
@@ -1643,7 +1642,7 @@ bool upb_msgdef_lookupname(const upb_msgdef *m, const char *name, size_t len,
 
   *o = upb_trygetoneof(upb_value_getptr(val));
   *f = upb_trygetfield(upb_value_getptr(val));
-  assert((*o != NULL) ^ (*f != NULL));  /* Exactly one of the two should be set. */
+  UPB_ASSERT((*o != NULL) ^ (*f != NULL));  /* Exactly one of the two should be set. */
   return true;
 }
 
@@ -1658,7 +1657,7 @@ int upb_msgdef_numoneofs(const upb_msgdef *m) {
 }
 
 void upb_msgdef_setmapentry(upb_msgdef *m, bool map_entry) {
-  assert(!upb_msgdef_isfrozen(m));
+  UPB_ASSERT(!upb_msgdef_isfrozen(m));
   m->map_entry = map_entry;
 }
 
@@ -1765,13 +1764,14 @@ err2:
   return NULL;
 }
 
-upb_oneofdef *upb_oneofdef_dup(const upb_oneofdef *o, const void *owner) {
+static upb_oneofdef *upb_oneofdef_dup(const upb_oneofdef *o,
+                                      const void *owner) {
   bool ok;
   upb_oneof_iter i;
   upb_oneofdef *newo = upb_oneofdef_new(owner);
   if (!newo) return NULL;
   ok = upb_oneofdef_setname(newo, upb_oneofdef_name(o), NULL);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   for (upb_oneof_begin(&i, o); !upb_oneof_done(&i); upb_oneof_next(&i)) {
     upb_fielddef *f = upb_fielddef_dup(upb_oneof_iter_field(&i), &f);
     if (!f || !upb_oneofdef_addfield(newo, f, &f, NULL)) {
@@ -1785,7 +1785,7 @@ upb_oneofdef *upb_oneofdef_dup(const upb_oneofdef *o, const void *owner) {
 const char *upb_oneofdef_name(const upb_oneofdef *o) { return o->name; }
 
 bool upb_oneofdef_setname(upb_oneofdef *o, const char *name, upb_status *s) {
-  assert(!upb_oneofdef_isfrozen(o));
+  UPB_ASSERT(!upb_oneofdef_isfrozen(o));
   if (upb_oneofdef_containingtype(o)) {
     upb_status_seterrmsg(s, "oneof already added to a message");
     return false;
@@ -1814,11 +1814,15 @@ int upb_oneofdef_numfields(const upb_oneofdef *o) {
   return upb_strtable_count(&o->ntof);
 }
 
+uint32_t upb_oneofdef_index(const upb_oneofdef *o) {
+  return o->index;
+}
+
 bool upb_oneofdef_addfield(upb_oneofdef *o, upb_fielddef *f,
                            const void *ref_donor,
                            upb_status *s) {
-  assert(!upb_oneofdef_isfrozen(o));
-  assert(!o->parent || !upb_msgdef_isfrozen(o->parent));
+  UPB_ASSERT(!upb_oneofdef_isfrozen(o));
+  UPB_ASSERT(!o->parent || !upb_msgdef_isfrozen(o->parent));
 
   /* This method is idempotent. Check if |f| is already part of this oneofdef
    * and return immediately if so. */
@@ -2088,6 +2092,7 @@ bool upb_filedef_adddef(upb_filedef *f, upb_def *def, const void *ref_donor,
   if (upb_inttable_push(&f->defs, upb_value_constptr(def))) {
     def->file = f;
     upb_ref2(def, f);
+    upb_ref2(f, def);
     if (ref_donor) upb_def_unref(def, ref_donor);
     if (def->type == UPB_DEF_MSG) {
       upb_downcast_msgdef_mutable(def)->syntax = f->syntax;
@@ -2108,9 +2113,357 @@ bool upb_filedef_adddep(upb_filedef *f, const upb_filedef *dep) {
     return false;
   }
 }
+
+void upb_symtab_free(upb_symtab *s) {
+  upb_strtable_iter i;
+  upb_strtable_begin(&i, &s->symtab);
+  for (; !upb_strtable_done(&i); upb_strtable_next(&i)) {
+    const upb_def *def = upb_value_getptr(upb_strtable_iter_value(&i));
+    upb_def_unref(def, s);
+  }
+  upb_strtable_uninit(&s->symtab);
+  upb_gfree(s);
+}
+
+upb_symtab *upb_symtab_new() {
+  upb_symtab *s = upb_gmalloc(sizeof(*s));
+  if (!s) {
+    return NULL;
+  }
+
+  upb_strtable_init(&s->symtab, UPB_CTYPE_PTR);
+  return s;
+}
+
+const upb_def *upb_symtab_lookup(const upb_symtab *s, const char *sym) {
+  upb_value v;
+  upb_def *ret = upb_strtable_lookup(&s->symtab, sym, &v) ?
+      upb_value_getptr(v) : NULL;
+  return ret;
+}
+
+const upb_msgdef *upb_symtab_lookupmsg(const upb_symtab *s, const char *sym) {
+  upb_value v;
+  upb_def *def = upb_strtable_lookup(&s->symtab, sym, &v) ?
+      upb_value_getptr(v) : NULL;
+  return def ? upb_dyncast_msgdef(def) : NULL;
+}
+
+const upb_enumdef *upb_symtab_lookupenum(const upb_symtab *s, const char *sym) {
+  upb_value v;
+  upb_def *def = upb_strtable_lookup(&s->symtab, sym, &v) ?
+      upb_value_getptr(v) : NULL;
+  return def ? upb_dyncast_enumdef(def) : NULL;
+}
+
+/* Given a symbol and the base symbol inside which it is defined, find the
+ * symbol's definition in t. */
+static upb_def *upb_resolvename(const upb_strtable *t,
+                                const char *base, const char *sym) {
+  if(strlen(sym) == 0) return NULL;
+  if(sym[0] == '.') {
+    /* Symbols starting with '.' are absolute, so we do a single lookup.
+     * Slice to omit the leading '.' */
+    upb_value v;
+    return upb_strtable_lookup(t, sym + 1, &v) ? upb_value_getptr(v) : NULL;
+  } else {
+    /* Remove components from base until we find an entry or run out.
+     * TODO: This branch is totally broken, but currently not used. */
+    (void)base;
+    UPB_ASSERT(false);
+    return NULL;
+  }
+}
+
+const upb_def *upb_symtab_resolve(const upb_symtab *s, const char *base,
+                                  const char *sym) {
+  upb_def *ret = upb_resolvename(&s->symtab, base, sym);
+  return ret;
+}
+
+/* TODO(haberman): we need a lot more testing of error conditions. */
+static bool symtab_add(upb_symtab *s, upb_def *const*defs, size_t n,
+                       void *ref_donor, upb_refcounted *freeze_also,
+                       upb_status *status) {
+  size_t i;
+  size_t add_n;
+  size_t freeze_n;
+  upb_strtable_iter iter;
+  upb_refcounted **add_objs = NULL;
+  upb_def **add_defs = NULL;
+  size_t add_objs_size;
+  upb_strtable addtab;
+
+  if (n == 0 && !freeze_also) {
+    return true;
+  }
+
+  if (!upb_strtable_init(&addtab, UPB_CTYPE_PTR)) {
+    upb_status_seterrmsg(status, "out of memory");
+    return false;
+  }
+
+  /* Add new defs to our "add" set. */
+  for (i = 0; i < n; i++) {
+    upb_def *def = defs[i];
+    const char *fullname;
+    upb_fielddef *f;
+
+    if (upb_def_isfrozen(def)) {
+      upb_status_seterrmsg(status, "added defs must be mutable");
+      goto err;
+    }
+    UPB_ASSERT(!upb_def_isfrozen(def));
+    fullname = upb_def_fullname(def);
+    if (!fullname) {
+      upb_status_seterrmsg(
+          status, "Anonymous defs cannot be added to a symtab");
+      goto err;
+    }
+
+    f = upb_dyncast_fielddef_mutable(def);
+
+    if (f) {
+      if (!upb_fielddef_containingtypename(f)) {
+        upb_status_seterrmsg(status,
+                             "Standalone fielddefs must have a containing type "
+                             "(extendee) name set");
+        goto err;
+      }
+    } else {
+      if (upb_strtable_lookup(&addtab, fullname, NULL)) {
+        upb_status_seterrf(status, "Conflicting defs named '%s'", fullname);
+        goto err;
+      }
+      if (upb_strtable_lookup(&s->symtab, fullname, NULL)) {
+        upb_status_seterrf(status, "Symtab already has a def named '%s'",
+                           fullname);
+        goto err;
+      }
+      upb_def_donateref(def, ref_donor, s);
+      if (!upb_strtable_insert(&addtab, fullname, upb_value_ptr(def)))
+        goto oom_err;
+      def->came_from_user = true;
+    }
+  }
+
+  /* Add standalone fielddefs (ie. extensions) to the appropriate messages.
+   * If the appropriate message only exists in the existing symtab, duplicate
+   * it so we have a mutable copy we can add the fields to. */
+  for (i = 0; i < n; i++) {
+    upb_def *def = defs[i];
+    upb_fielddef *f = upb_dyncast_fielddef_mutable(def);
+    const char *msgname;
+    upb_value v;
+    upb_msgdef *m;
+
+    if (!f) continue;
+    msgname = upb_fielddef_containingtypename(f);
+    /* We validated this earlier in this function. */
+    UPB_ASSERT(msgname);
+
+    /* If the extendee name is absolutely qualified, move past the initial ".".
+     * TODO(haberman): it is not obvious what it would mean if this was not
+     * absolutely qualified. */
+    if (msgname[0] == '.') {
+      msgname++;
+    }
+
+    if (upb_strtable_lookup(&addtab, msgname, &v)) {
+      /* Extendee is in the set of defs the user asked us to add. */
+      m = upb_value_getptr(v);
+    } else {
+      /* Need to find and dup the extendee from the existing symtab. */
+      const upb_msgdef *frozen_m = upb_symtab_lookupmsg(s, msgname);
+      if (!frozen_m) {
+        upb_status_seterrf(status,
+                           "Tried to extend message %s that does not exist "
+                           "in this SymbolTable.",
+                           msgname);
+        goto err;
+      }
+      m = upb_msgdef_dup(frozen_m, s);
+      if (!m) goto oom_err;
+      if (!upb_strtable_insert(&addtab, msgname, upb_value_ptr(m))) {
+        upb_msgdef_unref(m, s);
+        goto oom_err;
+      }
+    }
+
+    if (!upb_msgdef_addfield(m, f, ref_donor, status)) {
+      goto err;
+    }
+  }
+
+  /* Now using the table, resolve symbolic references for subdefs. */
+  upb_strtable_begin(&iter, &addtab);
+  for (; !upb_strtable_done(&iter); upb_strtable_next(&iter)) {
+    const char *base;
+    upb_def *def = upb_value_getptr(upb_strtable_iter_value(&iter));
+    upb_msgdef *m = upb_dyncast_msgdef_mutable(def);
+    upb_msg_field_iter j;
+
+    if (!m) continue;
+    /* Type names are resolved relative to the message in which they appear. */
+    base = upb_msgdef_fullname(m);
+
+    for(upb_msg_field_begin(&j, m);
+        !upb_msg_field_done(&j);
+        upb_msg_field_next(&j)) {
+      upb_fielddef *f = upb_msg_iter_field(&j);
+      const char *name = upb_fielddef_subdefname(f);
+      if (name && !upb_fielddef_subdef(f)) {
+        /* Try the lookup in the current set of to-be-added defs first. If not
+         * there, try existing defs. */
+        upb_def *subdef = upb_resolvename(&addtab, base, name);
+        if (subdef == NULL) {
+          subdef = upb_resolvename(&s->symtab, base, name);
+        }
+        if (subdef == NULL) {
+          upb_status_seterrf(
+              status, "couldn't resolve name '%s' in message '%s'", name, base);
+          goto err;
+        } else if (!upb_fielddef_setsubdef(f, subdef, status)) {
+          goto err;
+        }
+      }
+    }
+  }
+
+  /* We need an array of the defs in addtab, for passing to
+   * upb_refcounted_freeze(). */
+  add_objs_size = upb_strtable_count(&addtab);
+  if (freeze_also) {
+    add_objs_size++;
+  }
+
+  add_defs = upb_gmalloc(sizeof(void*) * add_objs_size);
+  if (add_defs == NULL) goto oom_err;
+  upb_strtable_begin(&iter, &addtab);
+  for (add_n = 0; !upb_strtable_done(&iter); upb_strtable_next(&iter)) {
+    add_defs[add_n++] = upb_value_getptr(upb_strtable_iter_value(&iter));
+  }
+
+  /* Validate defs. */
+  if (!_upb_def_validate(add_defs, add_n, status)) {
+    goto err;
+  }
+
+  /* Cheat a little and give the array a new type.
+   * This is probably undefined behavior, but this code will be deleted soon. */
+  add_objs = (upb_refcounted**)add_defs;
+
+  freeze_n = add_n;
+  if (freeze_also) {
+    add_objs[freeze_n++] = freeze_also;
+  }
+
+  if (!upb_refcounted_freeze(add_objs, freeze_n, status,
+                             UPB_MAX_MESSAGE_DEPTH * 2)) {
+    goto err;
+  }
+
+  /* This must be delayed until all errors have been detected, since error
+   * recovery code uses this table to cleanup defs. */
+  upb_strtable_uninit(&addtab);
+
+  /* TODO(haberman) we don't properly handle errors after this point (like
+   * OOM in upb_strtable_insert() below). */
+  for (i = 0; i < add_n; i++) {
+    upb_def *def = (upb_def*)add_objs[i];
+    const char *name = upb_def_fullname(def);
+    upb_value v;
+    bool success;
+
+    if (upb_strtable_remove(&s->symtab, name, &v)) {
+      const upb_def *def = upb_value_getptr(v);
+      upb_def_unref(def, s);
+    }
+    success = upb_strtable_insert(&s->symtab, name, upb_value_ptr(def));
+    UPB_ASSERT(success == true);
+  }
+  upb_gfree(add_defs);
+  return true;
+
+oom_err:
+  upb_status_seterrmsg(status, "out of memory");
+err: {
+    /* We need to donate the refs back. */
+    upb_strtable_begin(&iter, &addtab);
+    for (; !upb_strtable_done(&iter); upb_strtable_next(&iter)) {
+      upb_def *def = upb_value_getptr(upb_strtable_iter_value(&iter));
+      upb_def_donateref(def, s, ref_donor);
+    }
+  }
+  upb_strtable_uninit(&addtab);
+  upb_gfree(add_defs);
+  UPB_ASSERT(!upb_ok(status));
+  return false;
+}
+
+bool upb_symtab_add(upb_symtab *s, upb_def *const*defs, size_t n,
+                    void *ref_donor, upb_status *status) {
+  return symtab_add(s, defs, n, ref_donor, NULL, status);
+}
+
+bool upb_symtab_addfile(upb_symtab *s, upb_filedef *file, upb_status *status) {
+  size_t n;
+  size_t i;
+  upb_def **defs;
+  bool ret;
+
+  n = upb_filedef_defcount(file);
+  defs = upb_gmalloc(sizeof(*defs) * n);
+
+  if (defs == NULL) {
+    upb_status_seterrmsg(status, "Out of memory");
+    return false;
+  }
+
+  for (i = 0; i < n; i++) {
+    defs[i] = upb_filedef_mutabledef(file, i);
+  }
+
+  ret = symtab_add(s, defs, n, NULL, upb_filedef_upcast_mutable(file), status);
+
+  upb_gfree(defs);
+  return ret;
+}
+
+/* Iteration. */
+
+static void advance_to_matching(upb_symtab_iter *iter) {
+  if (iter->type == UPB_DEF_ANY)
+    return;
+
+  while (!upb_strtable_done(&iter->iter) &&
+         iter->type != upb_symtab_iter_def(iter)->type) {
+    upb_strtable_next(&iter->iter);
+  }
+}
+
+void upb_symtab_begin(upb_symtab_iter *iter, const upb_symtab *s,
+                      upb_deftype_t type) {
+  upb_strtable_begin(&iter->iter, &s->symtab);
+  iter->type = type;
+  advance_to_matching(iter);
+}
+
+void upb_symtab_next(upb_symtab_iter *iter) {
+  upb_strtable_next(&iter->iter);
+  advance_to_matching(iter);
+}
+
+bool upb_symtab_done(const upb_symtab_iter *iter) {
+  return upb_strtable_done(&iter->iter);
+}
+
+const upb_def *upb_symtab_iter_def(const upb_symtab_iter *iter) {
+  return upb_value_getptr(upb_strtable_iter_value(&iter->iter));
+}
 /*
 ** TODO(haberman): it's unclear whether a lot of the consistency checks should
-** assert() or return false.
+** UPB_ASSERT() or return false.
 */
 
 
@@ -2220,7 +2573,7 @@ oom:
 static int32_t trygetsel(upb_handlers *h, const upb_fielddef *f,
                          upb_handlertype_t type) {
   upb_selector_t sel;
-  assert(!upb_handlers_isfrozen(h));
+  UPB_ASSERT(!upb_handlers_isfrozen(h));
   if (upb_handlers_msgdef(h) != upb_fielddef_containingtype(f)) {
     upb_status_seterrf(
         &h->status_, "type mismatch: field %s does not belong to message %s",
@@ -2240,7 +2593,7 @@ static int32_t trygetsel(upb_handlers *h, const upb_fielddef *f,
 static upb_selector_t handlers_getsel(upb_handlers *h, const upb_fielddef *f,
                              upb_handlertype_t type) {
   int32_t sel = trygetsel(h, f, type);
-  assert(sel >= 0);
+  UPB_ASSERT(sel >= 0);
   return sel;
 }
 
@@ -2256,7 +2609,7 @@ static bool doset(upb_handlers *h, int32_t sel, const upb_fielddef *f,
   const void *closure_type;
   const void **context_closure_type;
 
-  assert(!upb_handlers_isfrozen(h));
+  UPB_ASSERT(!upb_handlers_isfrozen(h));
 
   if (sel < 0) {
     upb_status_seterrmsg(&h->status_,
@@ -2336,7 +2689,7 @@ const void *effective_closure_type(upb_handlers *h, const upb_fielddef *f,
   const void *ret;
   upb_selector_t sel;
 
-  assert(type != UPB_HANDLER_STRING);
+  UPB_ASSERT(type != UPB_HANDLER_STRING);
   ret = h->top_closure_type;
 
   if (upb_fielddef_isseq(f) &&
@@ -2391,7 +2744,7 @@ upb_handlers *upb_handlers_new(const upb_msgdef *md, const void *owner) {
   int extra;
   upb_handlers *h;
 
-  assert(upb_msgdef_isfrozen(md));
+  UPB_ASSERT(upb_msgdef_isfrozen(md));
 
   extra = sizeof(upb_handlers_tabent) * (md->selector_count - 1);
   h = upb_calloc(sizeof(*h) + extra);
@@ -2440,18 +2793,18 @@ const upb_handlers *upb_handlers_newfrozen(const upb_msgdef *m,
 
   r = upb_handlers_upcast_mutable(ret);
   ok = upb_refcounted_freeze(&r, 1, NULL, UPB_MAX_HANDLER_DEPTH);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
 
   return ret;
 }
 
 const upb_status *upb_handlers_status(upb_handlers *h) {
-  assert(!upb_handlers_isfrozen(h));
+  UPB_ASSERT(!upb_handlers_isfrozen(h));
   return &h->status_;
 }
 
 void upb_handlers_clearerr(upb_handlers *h) {
-  assert(!upb_handlers_isfrozen(h));
+  UPB_ASSERT(!upb_handlers_isfrozen(h));
   upb_status_clear(&h->status_);
 }
 
@@ -2487,16 +2840,16 @@ bool upb_handlers_setstartmsg(upb_handlers *h, upb_startmsg_handlerfunc *func,
 
 bool upb_handlers_setendmsg(upb_handlers *h, upb_endmsg_handlerfunc *func,
                             upb_handlerattr *attr) {
-  assert(!upb_handlers_isfrozen(h));
+  UPB_ASSERT(!upb_handlers_isfrozen(h));
   return doset(h, UPB_ENDMSG_SELECTOR, NULL, UPB_HANDLER_INT32,
                (upb_func *)func, attr);
 }
 
 bool upb_handlers_setsubhandlers(upb_handlers *h, const upb_fielddef *f,
                                  const upb_handlers *sub) {
-  assert(sub);
-  assert(!upb_handlers_isfrozen(h));
-  assert(upb_fielddef_issubmsg(f));
+  UPB_ASSERT(sub);
+  UPB_ASSERT(!upb_handlers_isfrozen(h));
+  UPB_ASSERT(upb_fielddef_issubmsg(f));
   if (SUBH_F(h, f)) return false;  /* Can't reset. */
   if (upb_msgdef_upcast(upb_handlers_msgdef(sub)) != upb_fielddef_subdef(f)) {
     return false;
@@ -2508,7 +2861,7 @@ bool upb_handlers_setsubhandlers(upb_handlers *h, const upb_fielddef *f,
 
 const upb_handlers *upb_handlers_getsubhandlers(const upb_handlers *h,
                                                 const upb_fielddef *f) {
-  assert(upb_fielddef_issubmsg(f));
+  UPB_ASSERT(upb_fielddef_issubmsg(f));
   return SUBH_F(h, f);
 }
 
@@ -2534,7 +2887,7 @@ bool upb_handlers_addcleanup(upb_handlers *h, void *p, upb_handlerfree *func) {
     return false;
   }
   ok = upb_inttable_insertptr(&h->cleanup_, p, upb_value_fptr(func));
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return true;
 }
 
@@ -2635,7 +2988,7 @@ upb_handlertype_t upb_handlers_getprimitivehandlertype(const upb_fielddef *f) {
     case UPB_TYPE_FLOAT: return UPB_HANDLER_FLOAT;
     case UPB_TYPE_DOUBLE: return UPB_HANDLER_DOUBLE;
     case UPB_TYPE_BOOL: return UPB_HANDLER_BOOL;
-    default: assert(false); return -1;  /* Invalid input. */
+    default: UPB_ASSERT(false); return -1;  /* Invalid input. */
   }
 }
 
@@ -2698,7 +3051,7 @@ bool upb_handlers_getselector(const upb_fielddef *f, upb_handlertype_t type,
       *s = f->selector_base;
       break;
   }
-  assert((size_t)*s < upb_fielddef_containingtype(f)->selector_count);
+  UPB_ASSERT((size_t)*s < upb_fielddef_containingtype(f)->selector_count);
   return true;
 }
 
@@ -2803,6 +3156,1216 @@ bool upb_byteshandler_setendstr(upb_byteshandler *h,
   h->table[UPB_ENDSTR_SELECTOR].attr.handler_data_ = d;
   return true;
 }
+
+
+static bool is_power_of_two(size_t val) {
+  return (val & (val - 1)) == 0;
+}
+
+/* Align up to the given power of 2. */
+static size_t align_up(size_t val, size_t align) {
+  UPB_ASSERT(is_power_of_two(align));
+  return (val + align - 1) & ~(align - 1);
+}
+
+static size_t div_round_up(size_t n, size_t d) {
+  return (n + d - 1) / d;
+}
+
+bool upb_fieldtype_mapkeyok(upb_fieldtype_t type) {
+  return type == UPB_TYPE_BOOL || type == UPB_TYPE_INT32 ||
+         type == UPB_TYPE_UINT32 || type == UPB_TYPE_INT64 ||
+         type == UPB_TYPE_UINT64 || type == UPB_TYPE_STRING;
+}
+
+void *upb_array_pack(const upb_array *arr, void *p, size_t *ofs, size_t size);
+void *upb_map_pack(const upb_map *map, void *p, size_t *ofs, size_t size);
+
+#define CHARPTR_AT(msg, ofs) ((char*)msg + ofs)
+#define ENCODE_MAX_NESTING 64
+#define CHECK_TRUE(x) if (!(x)) { return false; }
+
+/** upb_msgval ****************************************************************/
+
+#define upb_alignof(t) offsetof(struct { char c; t x; }, x)
+
+/* These functions will generate real memcpy() calls on ARM sadly, because
+ * the compiler assumes they might not be aligned. */
+
+static upb_msgval upb_msgval_read(const void *p, size_t ofs,
+                                  uint8_t size) {
+  upb_msgval val;
+  p = (char*)p + ofs;
+  memcpy(&val, p, size);
+  return val;
+}
+
+static void upb_msgval_write(void *p, size_t ofs, upb_msgval val,
+                             uint8_t size) {
+  p = (char*)p + ofs;
+  memcpy(p, &val, size);
+}
+
+static size_t upb_msgval_sizeof(upb_fieldtype_t type) {
+  switch (type) {
+    case UPB_TYPE_DOUBLE:
+    case UPB_TYPE_INT64:
+    case UPB_TYPE_UINT64:
+      return 8;
+    case UPB_TYPE_ENUM:
+    case UPB_TYPE_INT32:
+    case UPB_TYPE_UINT32:
+    case UPB_TYPE_FLOAT:
+      return 4;
+    case UPB_TYPE_BOOL:
+      return 1;
+    case UPB_TYPE_BYTES:
+    case UPB_TYPE_MESSAGE:
+      return sizeof(void*);
+    case UPB_TYPE_STRING:
+      return sizeof(char*) + sizeof(size_t);
+  }
+  UPB_UNREACHABLE();
+}
+
+static uint8_t upb_msg_fieldsize(const upb_fielddef *f) {
+  if (upb_fielddef_isseq(f)) {
+    return sizeof(void*);
+  } else {
+    return upb_msgval_sizeof(upb_fielddef_type(f));
+  }
+}
+
+/* TODO(haberman): this is broken right now because upb_msgval can contain
+ * a char* / size_t pair, which is too big for a upb_value.  To fix this
+ * we'll probably need to dynamically allocate a upb_msgval and store a
+ * pointer to that in the tables for extensions/maps. */
+static upb_value upb_toval(upb_msgval val) {
+  upb_value ret;
+  UPB_UNUSED(val);
+  memset(&ret, 0, sizeof(upb_value));  /* XXX */
+  return ret;
+}
+
+static upb_msgval upb_msgval_fromval(upb_value val) {
+  upb_msgval ret;
+  UPB_UNUSED(val);
+  memset(&ret, 0, sizeof(upb_msgval));  /* XXX */
+  return ret;
+}
+
+static upb_ctype_t upb_fieldtotabtype(upb_fieldtype_t type) {
+  switch (type) {
+    case UPB_TYPE_FLOAT: return UPB_CTYPE_FLOAT;
+    case UPB_TYPE_DOUBLE: return UPB_CTYPE_DOUBLE;
+    case UPB_TYPE_BOOL: return UPB_CTYPE_BOOL;
+    case UPB_TYPE_BYTES:
+    case UPB_TYPE_MESSAGE:
+    case UPB_TYPE_STRING: return UPB_CTYPE_CONSTPTR;
+    case UPB_TYPE_ENUM:
+    case UPB_TYPE_INT32: return UPB_CTYPE_INT32;
+    case UPB_TYPE_UINT32: return UPB_CTYPE_UINT32;
+    case UPB_TYPE_INT64: return UPB_CTYPE_INT64;
+    case UPB_TYPE_UINT64: return UPB_CTYPE_UINT64;
+    default: UPB_ASSERT(false); return 0;
+  }
+}
+
+static upb_msgval upb_msgval_fromdefault(const upb_fielddef *f) {
+  /* TODO(haberman): improve/optimize this (maybe use upb_msgval in fielddef) */
+  switch (upb_fielddef_type(f)) {
+      case UPB_TYPE_FLOAT:
+        return upb_msgval_float(upb_fielddef_defaultfloat(f));
+      case UPB_TYPE_DOUBLE:
+        return upb_msgval_double(upb_fielddef_defaultdouble(f));
+      case UPB_TYPE_BOOL:
+        return upb_msgval_bool(upb_fielddef_defaultbool(f));
+      case UPB_TYPE_STRING:
+      case UPB_TYPE_BYTES: {
+        size_t len;
+        const char *ptr = upb_fielddef_defaultstr(f, &len);
+        return upb_msgval_str(ptr, len);
+      }
+      case UPB_TYPE_MESSAGE:
+        return upb_msgval_msg(NULL);
+      case UPB_TYPE_ENUM:
+      case UPB_TYPE_INT32:
+        return upb_msgval_int32(upb_fielddef_defaultint32(f));
+      case UPB_TYPE_UINT32:
+        return upb_msgval_uint32(upb_fielddef_defaultuint32(f));
+      case UPB_TYPE_INT64:
+        return upb_msgval_int64(upb_fielddef_defaultint64(f));
+      case UPB_TYPE_UINT64:
+        return upb_msgval_uint64(upb_fielddef_defaultuint64(f));
+      default:
+        UPB_ASSERT(false);
+        return upb_msgval_msg(NULL);
+  }
+}
+
+
+/** upb_msglayout *************************************************************/
+
+struct upb_msglayout {
+  upb_msgfactory *factory;
+  const upb_msgdef *msgdef;
+  size_t size;
+  size_t extdict_offset;
+  void *default_msg;
+  uint32_t *field_offsets;
+  uint32_t *case_offsets;
+  uint32_t *hasbits;
+  bool has_extdict;
+  uint8_t align;
+};
+
+static void upb_msg_checkfield(const upb_msglayout *l, const upb_fielddef *f) {
+  UPB_ASSERT(l->msgdef == upb_fielddef_containingtype(f));
+}
+
+static void upb_msglayout_free(upb_msglayout *l) {
+  upb_gfree(l->default_msg);
+  upb_gfree(l);
+}
+
+const upb_msgdef *upb_msglayout_msgdef(const upb_msglayout *l) {
+  return l->msgdef;
+}
+
+static size_t upb_msglayout_place(upb_msglayout *l, size_t size) {
+  size_t ret;
+
+  l->size = align_up(l->size, size);
+  l->align = align_up(l->align, size);
+  ret = l->size;
+  l->size += size;
+  return ret;
+}
+
+static uint32_t upb_msglayout_offset(const upb_msglayout *l,
+                                     const upb_fielddef *f) {
+  return l->field_offsets[upb_fielddef_index(f)];
+}
+
+static uint32_t upb_msglayout_hasbit(const upb_msglayout *l,
+                                     const upb_fielddef *f) {
+  return l->hasbits[upb_fielddef_index(f)];
+}
+
+static bool upb_msglayout_initdefault(upb_msglayout *l) {
+  const upb_msgdef *m = l->msgdef;
+  upb_msg_field_iter it;
+
+  if (upb_msgdef_syntax(m) == UPB_SYNTAX_PROTO2 && l->size) {
+    /* Allocate default message and set default values in it. */
+    l->default_msg = upb_gmalloc(l->size);
+    if (!l->default_msg) {
+      return false;
+    }
+
+    memset(l->default_msg, 0, l->size);
+
+    for (upb_msg_field_begin(&it, m); !upb_msg_field_done(&it);
+         upb_msg_field_next(&it)) {
+      const upb_fielddef* f = upb_msg_iter_field(&it);
+
+      if (upb_fielddef_containingoneof(f)) {
+        continue;
+      }
+
+      if (!upb_fielddef_isstring(f) &&
+          !upb_fielddef_issubmsg(f) &&
+          !upb_fielddef_isseq(f)) {
+        upb_msg_set(l->default_msg, f, upb_msgval_fromdefault(f), l);
+      }
+    }
+  }
+
+  return true;
+}
+
+static upb_msglayout *upb_msglayout_new(const upb_msgdef *m) {
+  upb_msg_field_iter it;
+  upb_msg_oneof_iter oit;
+  upb_msglayout *l;
+  size_t hasbit;
+  size_t array_size = upb_msgdef_numfields(m) + upb_msgdef_numoneofs(m);
+
+  if (upb_msgdef_syntax(m) == UPB_SYNTAX_PROTO2) {
+    array_size += upb_msgdef_numfields(m);  /* hasbits. */
+  }
+
+  l = upb_gmalloc(sizeof(*l) + (sizeof(uint32_t) * array_size));
+  if (!l) return NULL;
+
+  memset(l, 0, sizeof(*l));
+
+  l->msgdef = m;
+  l->align = 1;
+  l->field_offsets = (uint32_t*)CHARPTR_AT(l, sizeof(*l));
+  l->case_offsets = l->field_offsets + upb_msgdef_numfields(m);
+  l->hasbits = l->case_offsets + upb_msgdef_numoneofs(m);
+
+  /* Allocate data offsets in three stages:
+   *
+   * 1. hasbits.
+   * 2. regular fields.
+   * 3. oneof fields.
+   *
+   * OPT: There is a lot of room for optimization here to minimize the size.
+   */
+
+  /* Allocate hasbits.  Start at sizeof(void*) for upb_alloc*. */
+  for (upb_msg_field_begin(&it, m), hasbit = sizeof(void*) * 8;
+       !upb_msg_field_done(&it);
+       upb_msg_field_next(&it)) {
+    const upb_fielddef* f = upb_msg_iter_field(&it);
+
+    if (upb_fielddef_haspresence(f) && !upb_fielddef_containingoneof(f)) {
+      l->hasbits[upb_fielddef_index(f)] = hasbit++;
+    }
+  }
+
+  /* Account for space used by hasbits. */
+  l->size = div_round_up(hasbit, 8);
+
+  /* Allocate non-oneof fields. */
+  for (upb_msg_field_begin(&it, m); !upb_msg_field_done(&it);
+       upb_msg_field_next(&it)) {
+    const upb_fielddef* f = upb_msg_iter_field(&it);
+    size_t field_size = upb_msg_fieldsize(f);
+    size_t index = upb_fielddef_index(f);
+
+
+    if (upb_fielddef_containingoneof(f)) {
+      /* Oneofs are handled separately below. */
+      continue;
+    }
+
+    l->field_offsets[index] = upb_msglayout_place(l, field_size);
+  }
+
+  /* Allocate oneof fields.  Each oneof field consists of a uint32 for the case
+   * and space for the actual data. */
+  for (upb_msg_oneof_begin(&oit, m); !upb_msg_oneof_done(&oit);
+       upb_msg_oneof_next(&oit)) {
+    const upb_oneofdef* oneof = upb_msg_iter_oneof(&oit);
+    upb_oneof_iter fit;
+    size_t case_size = sizeof(uint32_t);  /* Could potentially optimize this. */
+    size_t field_size = 0;
+    size_t case_offset;
+    size_t val_offset;
+
+    /* Calculate field size: the max of all field sizes. */
+    for (upb_oneof_begin(&fit, oneof);
+         !upb_oneof_done(&fit);
+         upb_oneof_next(&fit)) {
+      const upb_fielddef* f = upb_oneof_iter_field(&fit);
+      field_size = UPB_MAX(field_size, upb_msg_fieldsize(f));
+    }
+
+    /* Align and allocate case offset. */
+    case_offset = upb_msglayout_place(l, case_size);
+    val_offset = upb_msglayout_place(l, field_size);
+
+    l->case_offsets[upb_oneofdef_index(oneof)] = case_offset;
+
+    /* Assign all fields in the oneof this same offset. */
+    for (upb_oneof_begin(&fit, oneof); !upb_oneof_done(&fit);
+         upb_oneof_next(&fit)) {
+      const upb_fielddef* f = upb_oneof_iter_field(&fit);
+      l->field_offsets[upb_fielddef_index(f)] = val_offset;
+    }
+  }
+
+  /* Size of the entire structure should be a multiple of its greatest
+   * alignment. */
+  l->size = align_up(l->size, l->align);
+
+  if (upb_msglayout_initdefault(l)) {
+    return l;
+  } else {
+    upb_msglayout_free(l);
+    return NULL;
+  }
+}
+
+upb_msgfactory *upb_msglayout_factory(const upb_msglayout *layout) {
+  return layout->factory;
+}
+
+
+/** upb_msgfactory ************************************************************/
+
+struct upb_msgfactory {
+  const upb_symtab *symtab;  /* We own a ref. */
+  upb_inttable layouts;
+  upb_inttable mergehandlers;
+};
+
+upb_msgfactory *upb_msgfactory_new(const upb_symtab *symtab) {
+  upb_msgfactory *ret = upb_gmalloc(sizeof(*ret));
+
+  ret->symtab = symtab;
+  upb_inttable_init(&ret->layouts, UPB_CTYPE_PTR);
+  upb_inttable_init(&ret->mergehandlers, UPB_CTYPE_CONSTPTR);
+
+  return ret;
+}
+
+void upb_msgfactory_free(upb_msgfactory *f) {
+  upb_inttable_iter i;
+  upb_inttable_begin(&i, &f->layouts);
+  for(; !upb_inttable_done(&i); upb_inttable_next(&i)) {
+    upb_msglayout *l = upb_value_getptr(upb_inttable_iter_value(&i));
+    upb_msglayout_free(l);
+  }
+
+  upb_inttable_begin(&i, &f->mergehandlers);
+  for(; !upb_inttable_done(&i); upb_inttable_next(&i)) {
+    const upb_handlers *h = upb_value_getconstptr(upb_inttable_iter_value(&i));
+    upb_handlers_unref(h, f);
+  }
+
+  upb_inttable_uninit(&f->layouts);
+  upb_inttable_uninit(&f->mergehandlers);
+  upb_gfree(f);
+}
+
+const upb_symtab *upb_msgfactory_symtab(const upb_msgfactory *f) {
+  return f->symtab;
+}
+
+const upb_msglayout *upb_msgfactory_getlayout(upb_msgfactory *f,
+                                              const upb_msgdef *m) {
+  upb_value v;
+  UPB_ASSERT(upb_symtab_lookupmsg(f->symtab, upb_msgdef_fullname(m)) == m);
+  UPB_ASSERT(!upb_msgdef_mapentry(m));
+
+  if (upb_inttable_lookupptr(&f->layouts, m, &v)) {
+    UPB_ASSERT(upb_value_getptr(v));
+    return upb_value_getptr(v);
+  } else {
+    upb_msgfactory *mutable_f = (void*)f;
+    upb_msglayout *l = upb_msglayout_new(m);
+    upb_inttable_insertptr(&mutable_f->layouts, m, upb_value_ptr(l));
+    UPB_ASSERT(l);
+    l->factory = f;
+    return l;
+  }
+}
+
+/* Our handlers that we don't expose externally. */
+
+void *upb_msg_startstr(void *msg, const void *hd, size_t size_hint) {
+  uint32_t ofs = (uintptr_t)hd;
+  /* We pass NULL here because we know we can get away with it. */
+  upb_alloc *alloc = upb_msg_alloc(msg, NULL);
+  upb_msgval val;
+  UPB_UNUSED(size_hint);
+
+  val = upb_msgval_read(msg, ofs, upb_msgval_sizeof(UPB_TYPE_STRING));
+
+  upb_free(alloc, (void*)val.str.ptr);
+  val.str.ptr = NULL;
+  val.str.len = 0;
+
+  upb_msgval_write(msg, ofs, val, upb_msgval_sizeof(UPB_TYPE_STRING));
+  return msg;
+}
+
+size_t upb_msg_str(void *msg, const void *hd, const char *ptr, size_t size,
+                   const upb_bufhandle *handle) {
+  uint32_t ofs = (uintptr_t)hd;
+  /* We pass NULL here because we know we can get away with it. */
+  upb_alloc *alloc = upb_msg_alloc(msg, NULL);
+  upb_msgval val;
+  size_t newsize;
+  UPB_UNUSED(handle);
+
+  val = upb_msgval_read(msg, ofs, upb_msgval_sizeof(UPB_TYPE_STRING));
+
+  newsize = val.str.len + size;
+  val.str.ptr = upb_realloc(alloc, (void*)val.str.ptr, val.str.len, newsize);
+
+  if (!val.str.ptr) {
+    return false;
+  }
+
+  memcpy((char*)val.str.ptr + val.str.len, ptr, size);
+  val.str.len = newsize;
+  upb_msgval_write(msg, ofs, val, upb_msgval_sizeof(UPB_TYPE_STRING));
+  return size;
+}
+
+static void callback(const void *closure, upb_handlers *h) {
+  upb_msgfactory *factory = (upb_msgfactory*)closure;
+  const upb_msgdef *md = upb_handlers_msgdef(h);
+  const upb_msglayout* layout = upb_msgfactory_getlayout(factory, md);
+  upb_msg_field_iter i;
+  UPB_UNUSED(factory);
+
+  for(upb_msg_field_begin(&i, md);
+      !upb_msg_field_done(&i);
+      upb_msg_field_next(&i)) {
+    const upb_fielddef *f = upb_msg_iter_field(&i);
+    size_t offset = upb_msglayout_offset(layout, f);
+    upb_handlerattr attr = UPB_HANDLERATTR_INITIALIZER;
+    upb_handlerattr_sethandlerdata(&attr, (void*)offset);
+
+    if (upb_fielddef_isseq(f)) {
+    } else if (upb_fielddef_isstring(f)) {
+      upb_handlers_setstartstr(h, f, upb_msg_startstr, &attr);
+      upb_handlers_setstring(h, f, upb_msg_str, &attr);
+    } else {
+      upb_msg_setscalarhandler(
+          h, f, offset, upb_msglayout_hasbit(layout, f));
+    }
+  }
+}
+
+const upb_handlers *upb_msgfactory_getmergehandlers(upb_msgfactory *f,
+                                                    const upb_msgdef *m) {
+  upb_msgfactory *mutable_f = (void*)f;
+
+  /* TODO(haberman): properly cache these. */
+  const upb_handlers *ret = upb_handlers_newfrozen(m, f, callback, f);
+  upb_inttable_push(&mutable_f->mergehandlers, upb_value_constptr(ret));
+
+  return ret;
+}
+
+const upb_visitorplan *upb_msgfactory_getvisitorplan(upb_msgfactory *f,
+                                                     const upb_handlers *h) {
+  const upb_msgdef *md = upb_handlers_msgdef(h);
+  return (const upb_visitorplan*)upb_msgfactory_getlayout(f, md);
+}
+
+
+/** upb_visitor ***************************************************************/
+
+struct upb_visitor {
+  const upb_msglayout *layout;
+  upb_sink *sink;
+};
+
+static upb_selector_t getsel2(const upb_fielddef *f, upb_handlertype_t type) {
+  upb_selector_t ret;
+  bool ok = upb_handlers_getselector(f, type, &ret);
+  UPB_ASSERT(ok);
+  return ret;
+}
+
+static bool upb_visitor_hasfield(const upb_msg *msg, const upb_fielddef *f,
+                                 const upb_msglayout *layout) {
+  if (upb_fielddef_isseq(f)) {
+    return upb_msgval_getarr(upb_msg_get(msg, f, layout)) != NULL;
+  } else if (upb_msgdef_syntax(upb_fielddef_containingtype(f)) ==
+             UPB_SYNTAX_PROTO2) {
+    return upb_msg_has(msg, f, layout);
+  } else {
+    upb_msgval val = upb_msg_get(msg, f, layout);
+    switch (upb_fielddef_type(f)) {
+      case UPB_TYPE_FLOAT:
+        return upb_msgval_getfloat(val) != 0;
+      case UPB_TYPE_DOUBLE:
+        return upb_msgval_getdouble(val) != 0;
+      case UPB_TYPE_BOOL:
+        return upb_msgval_getbool(val);
+      case UPB_TYPE_ENUM:
+      case UPB_TYPE_INT32:
+        return upb_msgval_getint32(val) != 0;
+      case UPB_TYPE_UINT32:
+        return upb_msgval_getuint32(val) != 0;
+      case UPB_TYPE_INT64:
+        return upb_msgval_getint64(val) != 0;
+      case UPB_TYPE_UINT64:
+        return upb_msgval_getuint64(val) != 0;
+      case UPB_TYPE_STRING:
+      case UPB_TYPE_BYTES:
+        return upb_msgval_getstr(val) && upb_msgval_getstrlen(val) > 0;
+      case UPB_TYPE_MESSAGE:
+        return upb_msgval_getmsg(val) != NULL;
+    }
+    UPB_UNREACHABLE();
+  }
+}
+
+static bool upb_visitor_visitmsg2(const upb_msg *msg,
+                                  const upb_msglayout *layout, upb_sink *sink,
+                                  int depth) {
+  const upb_msgdef *md = upb_msglayout_msgdef(layout);
+  upb_msg_field_iter i;
+  upb_status status;
+
+  upb_sink_startmsg(sink);
+
+  /* Protect against cycles (possible because users may freely reassign message
+   * and repeated fields) by imposing a maximum recursion depth. */
+  if (depth > ENCODE_MAX_NESTING) {
+    return false;
+  }
+
+  for (upb_msg_field_begin(&i, md);
+       !upb_msg_field_done(&i);
+       upb_msg_field_next(&i)) {
+    upb_fielddef *f = upb_msg_iter_field(&i);
+    upb_msgval val;
+
+    if (!upb_visitor_hasfield(msg, f, layout)) {
+      continue;
+    }
+
+    val = upb_msg_get(msg, f, layout);
+
+    if (upb_fielddef_isseq(f)) {
+      const upb_array *arr = upb_msgval_getarr(val);
+      UPB_ASSERT(arr);
+      /* TODO: putary(ary, f, sink, depth);*/
+    } else if (upb_fielddef_issubmsg(f)) {
+      const upb_map *map = upb_msgval_getmap(val);
+      UPB_ASSERT(map);
+      /* TODO: putmap(map, f, sink, depth);*/
+    } else if (upb_fielddef_isstring(f)) {
+      /* TODO putstr(); */
+    } else {
+      upb_selector_t sel = getsel2(f, upb_handlers_getprimitivehandlertype(f));
+      UPB_ASSERT(upb_fielddef_isprimitive(f));
+
+      switch (upb_fielddef_type(f)) {
+        case UPB_TYPE_FLOAT:
+          CHECK_TRUE(upb_sink_putfloat(sink, sel, upb_msgval_getfloat(val)));
+          break;
+        case UPB_TYPE_DOUBLE:
+          CHECK_TRUE(
+              upb_sink_putdouble(sink, sel, upb_msgval_getdouble(val)));
+          break;
+        case UPB_TYPE_BOOL:
+          CHECK_TRUE(upb_sink_putbool(sink, sel, upb_msgval_getbool(val)));
+          break;
+        case UPB_TYPE_ENUM:
+        case UPB_TYPE_INT32:
+          CHECK_TRUE(upb_sink_putint32(sink, sel, upb_msgval_getint32(val)));
+          break;
+        case UPB_TYPE_UINT32:
+          CHECK_TRUE(
+              upb_sink_putuint32(sink, sel, upb_msgval_getuint32(val)));
+          break;
+        case UPB_TYPE_INT64:
+          CHECK_TRUE(upb_sink_putint64(sink, sel, upb_msgval_getint64(val)));
+          break;
+        case UPB_TYPE_UINT64:
+          CHECK_TRUE(
+              upb_sink_putuint64(sink, sel, upb_msgval_getuint64(val)));
+          break;
+        case UPB_TYPE_STRING:
+        case UPB_TYPE_BYTES:
+        case UPB_TYPE_MESSAGE:
+          UPB_UNREACHABLE();
+      }
+    }
+  }
+
+  upb_sink_endmsg(sink, &status);
+  return true;
+}
+
+upb_visitor *upb_visitor_create(upb_env *e, const upb_visitorplan *vp,
+                                upb_sink *output) {
+  upb_visitor *visitor = upb_env_malloc(e, sizeof(*visitor));
+  visitor->layout = (const upb_msglayout*)vp;
+  visitor->sink = output;
+  return visitor;
+}
+
+bool upb_visitor_visitmsg(upb_visitor *visitor, const upb_msg *msg) {
+  return upb_visitor_visitmsg2(msg, visitor->layout, visitor->sink, 0);
+}
+
+
+/** upb_msg *******************************************************************/
+
+/* If we always read/write as a consistent type to each address, this shouldn't
+ * violate aliasing.
+ */
+#define DEREF(msg, ofs, type) *(type*)CHARPTR_AT(msg, ofs)
+
+static upb_inttable *upb_msg_trygetextdict(const upb_msg *msg,
+                                           const upb_msglayout *l) {
+  return l->has_extdict ? DEREF(msg, l->extdict_offset, upb_inttable*) : NULL;
+}
+
+static upb_inttable *upb_msg_getextdict(upb_msg *msg,
+                                        const upb_msglayout *l,
+                                        upb_alloc *a) {
+  upb_inttable *ext_dict;
+  UPB_ASSERT(l->has_extdict);
+
+  ext_dict = upb_msg_trygetextdict(msg, l);
+
+  if (!ext_dict) {
+    ext_dict = upb_malloc(a, sizeof(upb_inttable));
+
+    if (!ext_dict) {
+      return NULL;
+    }
+
+    /* Use an 8-byte type to ensure all bytes are copied. */
+    if (!upb_inttable_init2(ext_dict, UPB_CTYPE_INT64, a)) {
+      upb_free(a, ext_dict);
+      return NULL;
+    }
+
+    DEREF(msg, l->extdict_offset, upb_inttable*) = ext_dict;
+  }
+
+  return ext_dict;
+}
+
+static uint32_t upb_msg_getoneofint(const upb_msg *msg,
+                                    const upb_oneofdef *o,
+                                    const upb_msglayout *l) {
+  size_t oneof_ofs = l->case_offsets[upb_oneofdef_index(o)];
+  return DEREF(msg, oneof_ofs, uint8_t);
+}
+
+static void upb_msg_setoneofcase(const upb_msg *msg,
+                                 const upb_oneofdef *o,
+                                 const upb_msglayout *l,
+                                 uint32_t val) {
+  size_t oneof_ofs = l->case_offsets[upb_oneofdef_index(o)];
+  DEREF(msg, oneof_ofs, uint8_t) = val;
+}
+
+
+static bool upb_msg_oneofis(const upb_msg *msg, const upb_msglayout *l,
+                            const upb_oneofdef *o, const upb_fielddef *f) {
+  return upb_msg_getoneofint(msg, o, l) == upb_fielddef_number(f);
+}
+
+size_t upb_msg_sizeof(const upb_msglayout *l) { return l->size; }
+
+void upb_msg_init(upb_msg *msg, const upb_msglayout *l, upb_alloc *a) {
+  if (l->default_msg) {
+    memcpy(msg, l->default_msg, l->size);
+  } else {
+    memset(msg, 0, l->size);
+  }
+
+  /* Set arena pointer. */
+  memcpy(msg, &a, sizeof(a));
+}
+
+void upb_msg_uninit(upb_msg *msg, const upb_msglayout *l) {
+  upb_inttable *ext_dict = upb_msg_trygetextdict(msg, l);
+  if (ext_dict) {
+    upb_inttable_uninit2(ext_dict, upb_msg_alloc(msg, l));
+  }
+}
+
+upb_msg *upb_msg_new(const upb_msglayout *l, upb_alloc *a) {
+  upb_msg *msg = upb_malloc(a, upb_msg_sizeof(l));
+
+  if (msg) {
+    upb_msg_init(msg, l, a);
+  }
+
+  return msg;
+}
+
+void upb_msg_free(upb_msg *msg, const upb_msglayout *l) {
+  upb_msg_uninit(msg, l);
+  upb_free(upb_msg_alloc(msg, l), msg);
+}
+
+upb_alloc *upb_msg_alloc(const upb_msg *msg, const upb_msglayout *l) {
+  upb_alloc *alloc;
+  UPB_UNUSED(l);
+  memcpy(&alloc, msg, sizeof(alloc));
+  return alloc;
+}
+
+bool upb_msg_has(const upb_msg *msg,
+                 const upb_fielddef *f,
+                 const upb_msglayout *l) {
+  const upb_oneofdef *o;
+  upb_msg_checkfield(l, f);
+  UPB_ASSERT(upb_fielddef_haspresence(f));
+
+  if (upb_fielddef_isextension(f)) {
+    /* Extensions are set when they are present in the extension dict. */
+    upb_inttable *ext_dict = upb_msg_trygetextdict(msg, l);
+    upb_value v;
+    return ext_dict != NULL &&
+           upb_inttable_lookup32(ext_dict, upb_fielddef_number(f), &v);
+  } else if ((o = upb_fielddef_containingoneof(f)) != NULL) {
+    /* Oneofs are set when the oneof number is set to this field. */
+    return upb_msg_getoneofint(msg, o, l) == upb_fielddef_number(f);
+  } else {
+    /* Other fields are set when their hasbit is set. */
+    uint32_t hasbit = l->hasbits[upb_fielddef_index(f)];
+    return DEREF(msg, hasbit / 8, char) | (1 << (hasbit % 8));
+  }
+}
+
+upb_msgval upb_msg_get(const upb_msg *msg, const upb_fielddef *f,
+                       const upb_msglayout *l) {
+  upb_msg_checkfield(l, f);
+
+  if (upb_fielddef_isextension(f)) {
+    upb_inttable *ext_dict = upb_msg_trygetextdict(msg, l);
+    upb_value val;
+    if (upb_inttable_lookup32(ext_dict, upb_fielddef_number(f), &val)) {
+      return upb_msgval_fromval(val);
+    } else {
+      return upb_msgval_fromdefault(f);
+    }
+  } else {
+    size_t ofs = l->field_offsets[upb_fielddef_index(f)];
+    const upb_oneofdef *o = upb_fielddef_containingoneof(f);
+    upb_msgval ret;
+
+    if (o && !upb_msg_oneofis(msg, l, o, f)) {
+      /* Oneof defaults can't come from the message because the memory is reused
+       * by all types in the oneof. */
+      return upb_msgval_fromdefault(f);
+    }
+
+    ret = upb_msgval_read(msg, ofs, upb_msg_fieldsize(f));
+    return ret;
+  }
+}
+
+bool upb_msg_set(upb_msg *msg,
+                 const upb_fielddef *f,
+                 upb_msgval val,
+                 const upb_msglayout *l) {
+  upb_alloc *a = upb_msg_alloc(msg, l);
+  upb_msg_checkfield(l, f);
+
+  if (upb_fielddef_isextension(f)) {
+    /* TODO(haberman): introduce table API that can do this in one call. */
+    upb_inttable *ext = upb_msg_getextdict(msg, l, a);
+    upb_value val2 = upb_toval(val);
+    if (!upb_inttable_replace(ext, upb_fielddef_number(f), val2) &&
+        !upb_inttable_insert2(ext, upb_fielddef_number(f), val2, a)) {
+      return false;
+    }
+  } else {
+    size_t ofs = l->field_offsets[upb_fielddef_index(f)];
+    const upb_oneofdef *o = upb_fielddef_containingoneof(f);
+
+    if (o) {
+      upb_msg_setoneofcase(msg, o, l, upb_fielddef_number(f));
+    }
+
+    upb_msgval_write(msg, ofs, val, upb_msg_fieldsize(f));
+  }
+  return true;
+}
+
+
+/** upb_array *****************************************************************/
+
+struct upb_array {
+  upb_fieldtype_t type;
+  uint8_t element_size;
+  void *data;   /* Each element is element_size. */
+  size_t len;   /* Measured in elements. */
+  size_t size;  /* Measured in elements. */
+  upb_alloc *alloc;
+};
+
+#define DEREF_ARR(arr, i, type) ((type*)arr->data)[i]
+
+size_t upb_array_sizeof(upb_fieldtype_t type) {
+  UPB_UNUSED(type);
+  return sizeof(upb_array);
+}
+
+void upb_array_init(upb_array *arr, upb_fieldtype_t type, upb_alloc *alloc) {
+  arr->type = type;
+  arr->data = NULL;
+  arr->len = 0;
+  arr->size = 0;
+  arr->element_size = upb_msgval_sizeof(type);
+  arr->alloc = alloc;
+}
+
+void upb_array_uninit(upb_array *arr) {
+  upb_free(arr->alloc, arr->data);
+}
+
+upb_array *upb_array_new(upb_fieldtype_t type, upb_alloc *a) {
+  upb_array *ret = upb_malloc(a, upb_array_sizeof(type));
+
+  if (ret) {
+    upb_array_init(ret, type, a);
+  }
+
+  return ret;
+}
+
+void upb_array_free(upb_array *arr) {
+  upb_array_uninit(arr);
+  upb_free(arr->alloc, arr);
+}
+
+size_t upb_array_size(const upb_array *arr) {
+  return arr->len;
+}
+
+upb_fieldtype_t upb_array_type(const upb_array *arr) {
+  return arr->type;
+}
+
+upb_msgval upb_array_get(const upb_array *arr, size_t i) {
+  UPB_ASSERT(i < arr->len);
+  return upb_msgval_read(arr->data, i * arr->element_size, arr->element_size);
+}
+
+bool upb_array_set(upb_array *arr, size_t i, upb_msgval val) {
+  UPB_ASSERT(i <= arr->len);
+
+  if (i == arr->len) {
+    /* Extending the array. */
+
+    if (i == arr->size) {
+      /* Need to reallocate. */
+      size_t new_size = UPB_MAX(arr->size * 2, 8);
+      size_t new_bytes = new_size * arr->element_size;
+      size_t old_bytes = arr->size * arr->element_size;
+      upb_msgval *new_data =
+          upb_realloc(arr->alloc, arr->data, old_bytes, new_bytes);
+
+      if (!new_data) {
+        return false;
+      }
+
+      arr->data = new_data;
+      arr->size = new_size;
+    }
+
+    arr->len = i + 1;
+  }
+
+  upb_msgval_write(arr->data, i * arr->element_size, val, arr->element_size);
+  return true;
+}
+
+
+/** upb_map *******************************************************************/
+
+struct upb_map {
+  upb_fieldtype_t key_type;
+  upb_fieldtype_t val_type;
+  /* We may want to optimize this to use inttable where possible, for greater
+   * efficiency and lower memory footprint. */
+  upb_strtable strtab;
+  upb_alloc *alloc;
+};
+
+static void upb_map_tokey(upb_fieldtype_t type, upb_msgval *key,
+                          const char **out_key, size_t *out_len) {
+  switch (type) {
+    case UPB_TYPE_STRING:
+      /* Point to string data of the input key. */
+      *out_key = key->str.ptr;
+      *out_len = key->str.len;
+      return;
+    case UPB_TYPE_BOOL:
+    case UPB_TYPE_INT32:
+    case UPB_TYPE_UINT32:
+    case UPB_TYPE_INT64:
+    case UPB_TYPE_UINT64:
+      /* Point to the key itself.  XXX: big-endian. */
+      *out_key = (const char*)key;
+      *out_len = upb_msgval_sizeof(type);
+      return;
+    case UPB_TYPE_BYTES:
+    case UPB_TYPE_DOUBLE:
+    case UPB_TYPE_ENUM:
+    case UPB_TYPE_FLOAT:
+    case UPB_TYPE_MESSAGE:
+      break;  /* Cannot be a map key. */
+  }
+  UPB_UNREACHABLE();
+}
+
+static upb_msgval upb_map_fromkey(upb_fieldtype_t type, const char *key,
+                                  size_t len) {
+  switch (type) {
+    case UPB_TYPE_STRING:
+      return upb_msgval_str(key, len);
+    case UPB_TYPE_BOOL:
+    case UPB_TYPE_INT32:
+    case UPB_TYPE_UINT32:
+    case UPB_TYPE_INT64:
+    case UPB_TYPE_UINT64:
+      return upb_msgval_read(key, 0, upb_msgval_sizeof(type));
+    case UPB_TYPE_BYTES:
+    case UPB_TYPE_DOUBLE:
+    case UPB_TYPE_ENUM:
+    case UPB_TYPE_FLOAT:
+    case UPB_TYPE_MESSAGE:
+      break;  /* Cannot be a map key. */
+  }
+  UPB_UNREACHABLE();
+}
+
+size_t upb_map_sizeof(upb_fieldtype_t ktype, upb_fieldtype_t vtype) {
+  /* Size does not currently depend on key/value type. */
+  UPB_UNUSED(ktype);
+  UPB_UNUSED(vtype);
+  return sizeof(upb_map);
+}
+
+bool upb_map_init(upb_map *map, upb_fieldtype_t ktype, upb_fieldtype_t vtype,
+                  upb_alloc *a) {
+  upb_ctype_t vtabtype = upb_fieldtotabtype(vtype);
+  UPB_ASSERT(upb_fieldtype_mapkeyok(ktype));
+  map->key_type = ktype;
+  map->val_type = vtype;
+  map->alloc = a;
+
+  if (!upb_strtable_init2(&map->strtab, vtabtype, a)) {
+    return false;
+  }
+
+  return true;
+}
+
+void upb_map_uninit(upb_map *map) {
+  upb_strtable_uninit2(&map->strtab, map->alloc);
+}
+
+upb_map *upb_map_new(upb_fieldtype_t ktype, upb_fieldtype_t vtype,
+                     upb_alloc *a) {
+  upb_map *map = upb_malloc(a, upb_map_sizeof(ktype, vtype));
+
+  if (!map) {
+    return NULL;
+  }
+
+  if (!upb_map_init(map, ktype, vtype, a)) {
+    return NULL;
+  }
+
+  return map;
+}
+
+void upb_map_free(upb_map *map) {
+  upb_map_uninit(map);
+  upb_free(map->alloc, map);
+}
+
+size_t upb_map_size(const upb_map *map) {
+  return upb_strtable_count(&map->strtab);
+}
+
+upb_fieldtype_t upb_map_keytype(const upb_map *map) {
+  return map->key_type;
+}
+
+upb_fieldtype_t upb_map_valuetype(const upb_map *map) {
+  return map->val_type;
+}
+
+bool upb_map_get(const upb_map *map, upb_msgval key, upb_msgval *val) {
+  upb_value tabval;
+  const char *key_str;
+  size_t key_len;
+  bool ret;
+
+  upb_map_tokey(map->key_type, &key, &key_str, &key_len);
+  ret = upb_strtable_lookup2(&map->strtab, key_str, key_len, &tabval);
+  if (ret) {
+    memcpy(val, &tabval, sizeof(tabval));
+  }
+
+  return ret;
+}
+
+bool upb_map_set(upb_map *map, upb_msgval key, upb_msgval val,
+                 upb_msgval *removed) {
+  const char *key_str;
+  size_t key_len;
+  upb_value tabval = upb_toval(val);
+  upb_value removedtabval;
+  upb_alloc *a = map->alloc;
+
+  upb_map_tokey(map->key_type, &key, &key_str, &key_len);
+
+  /* TODO(haberman): add overwrite operation to minimize number of lookups. */
+  if (upb_strtable_lookup2(&map->strtab, key_str, key_len, NULL)) {
+    upb_strtable_remove3(&map->strtab, key_str, key_len, &removedtabval, a);
+    memcpy(&removed, &removedtabval, sizeof(removed));
+  }
+
+  return upb_strtable_insert3(&map->strtab, key_str, key_len, tabval, a);
+}
+
+bool upb_map_del(upb_map *map, upb_msgval key) {
+  const char *key_str;
+  size_t key_len;
+  upb_alloc *a = map->alloc;
+
+  upb_map_tokey(map->key_type, &key, &key_str, &key_len);
+  return upb_strtable_remove3(&map->strtab, key_str, key_len, NULL, a);
+}
+
+
+/** upb_mapiter ***************************************************************/
+
+struct upb_mapiter {
+  upb_strtable_iter iter;
+  upb_fieldtype_t key_type;
+};
+
+size_t upb_mapiter_sizeof() {
+  return sizeof(upb_mapiter);
+}
+
+void upb_mapiter_begin(upb_mapiter *i, const upb_map *map) {
+  upb_strtable_begin(&i->iter, &map->strtab);
+  i->key_type = map->key_type;
+}
+
+upb_mapiter *upb_mapiter_new(const upb_map *t, upb_alloc *a) {
+  upb_mapiter *ret = upb_malloc(a, upb_mapiter_sizeof());
+
+  if (!ret) {
+    return NULL;
+  }
+
+  upb_mapiter_begin(ret, t);
+  return ret;
+}
+
+void upb_mapiter_free(upb_mapiter *i, upb_alloc *a) {
+  upb_free(a, i);
+}
+
+void upb_mapiter_next(upb_mapiter *i) {
+  upb_strtable_next(&i->iter);
+}
+
+bool upb_mapiter_done(const upb_mapiter *i) {
+  return upb_strtable_done(&i->iter);
+}
+
+upb_msgval upb_mapiter_key(const upb_mapiter *i) {
+  return upb_map_fromkey(i->key_type, upb_strtable_iter_key(&i->iter),
+                         upb_strtable_iter_keylength(&i->iter));
+}
+
+upb_msgval upb_mapiter_value(const upb_mapiter *i) {
+  return upb_msgval_fromval(upb_strtable_iter_value(&i->iter));
+}
+
+void upb_mapiter_setdone(upb_mapiter *i) {
+  upb_strtable_iter_setdone(&i->iter);
+}
+
+bool upb_mapiter_isequal(const upb_mapiter *i1, const upb_mapiter *i2) {
+  return upb_strtable_iter_isequal(&i1->iter, &i2->iter);
+}
+
+
+/** Handlers for upb_msg ******************************************************/
+
+typedef struct {
+  size_t offset;
+  int32_t hasbit;
+} upb_msg_handlerdata;
+
+/* Fallback implementation if the handler is not specialized by the producer. */
+#define MSG_WRITER(type, ctype)                                               \
+  bool upb_msg_set ## type (void *c, const void *hd, ctype val) {             \
+    uint8_t *m = c;                                                           \
+    const upb_msg_handlerdata *d = hd;                                        \
+    if (d->hasbit > 0)                                                        \
+      *(uint8_t*)&m[d->hasbit / 8] |= 1 << (d->hasbit % 8);                   \
+    *(ctype*)&m[d->offset] = val;                                             \
+    return true;                                                              \
+  }                                                                           \
+
+MSG_WRITER(double, double)
+MSG_WRITER(float,  float)
+MSG_WRITER(int32,  int32_t)
+MSG_WRITER(int64,  int64_t)
+MSG_WRITER(uint32, uint32_t)
+MSG_WRITER(uint64, uint64_t)
+MSG_WRITER(bool,   bool)
+
+bool upb_msg_setscalarhandler(upb_handlers *h, const upb_fielddef *f,
+                              size_t offset, int32_t hasbit) {
+  upb_handlerattr attr = UPB_HANDLERATTR_INITIALIZER;
+  bool ok;
+
+  upb_msg_handlerdata *d = upb_gmalloc(sizeof(*d));
+  if (!d) return false;
+  d->offset = offset;
+  d->hasbit = hasbit;
+
+  upb_handlerattr_sethandlerdata(&attr, d);
+  upb_handlerattr_setalwaysok(&attr, true);
+  upb_handlers_addcleanup(h, d, upb_gfree);
+
+#define TYPE(u, l) \
+  case UPB_TYPE_##u: \
+    ok = upb_handlers_set##l(h, f, upb_msg_set##l, &attr); break;
+
+  ok = false;
+
+  switch (upb_fielddef_type(f)) {
+    TYPE(INT64,  int64);
+    TYPE(INT32,  int32);
+    TYPE(ENUM,   int32);
+    TYPE(UINT64, uint64);
+    TYPE(UINT32, uint32);
+    TYPE(DOUBLE, double);
+    TYPE(FLOAT,  float);
+    TYPE(BOOL,   bool);
+    default: UPB_ASSERT(false); break;
+  }
+#undef TYPE
+
+  upb_handlerattr_uninit(&attr);
+  return ok;
+}
+
+bool upb_msg_getscalarhandlerdata(const upb_handlers *h,
+                                  upb_selector_t s,
+                                  upb_fieldtype_t *type,
+                                  size_t *offset,
+                                  int32_t *hasbit) {
+  const upb_msg_handlerdata *d;
+  upb_func *f = upb_handlers_gethandler(h, s);
+
+  if ((upb_int64_handlerfunc*)f == upb_msg_setint64) {
+    *type = UPB_TYPE_INT64;
+  } else if ((upb_int32_handlerfunc*)f == upb_msg_setint32) {
+    *type = UPB_TYPE_INT32;
+  } else if ((upb_uint64_handlerfunc*)f == upb_msg_setuint64) {
+    *type = UPB_TYPE_UINT64;
+  } else if ((upb_uint32_handlerfunc*)f == upb_msg_setuint32) {
+    *type = UPB_TYPE_UINT32;
+  } else if ((upb_double_handlerfunc*)f == upb_msg_setdouble) {
+    *type = UPB_TYPE_DOUBLE;
+  } else if ((upb_float_handlerfunc*)f == upb_msg_setfloat) {
+    *type = UPB_TYPE_FLOAT;
+  } else if ((upb_bool_handlerfunc*)f == upb_msg_setbool) {
+    *type = UPB_TYPE_BOOL;
+  } else {
+    return false;
+  }
+
+  d = upb_handlers_gethandlerdata(h, s);
+  *offset = d->offset;
+  *hasbit = d->hasbit;
+  return true;
+}
 /*
 ** upb::RefCounted Implementation
 **
@@ -2938,7 +4501,7 @@ static trackedref *trackedref_new(bool is_ref2) {
 static void track(const upb_refcounted *r, const void *owner, bool ref2) {
   upb_value v;
 
-  assert(owner);
+  UPB_ASSERT(owner);
   if (owner == UPB_UNTRACKED_REF) return;
 
   upb_lock();
@@ -2949,8 +4512,8 @@ static void track(const upb_refcounted *r, const void *owner, bool ref2) {
      * tracking behavior we get with regular refs.  Since ref2s only happen
      * inside upb, we'll accept this limitation until/unless there is a really
      * difficult upb-internal bug that can't be figured out without it. */
-    assert(ref2);
-    assert(ref->is_ref2);
+    UPB_ASSERT(ref2);
+    UPB_ASSERT(ref->is_ref2);
     ref->count++;
   } else {
     trackedref *ref = trackedref_new(ref2);
@@ -2960,7 +4523,7 @@ static void track(const upb_refcounted *r, const void *owner, bool ref2) {
       /* We know this cast is safe when it is a ref2, because it's coming from
        * another refcounted object. */
       const upb_refcounted *from = owner;
-      assert(!upb_inttable_lookupptr(from->ref2s, r, NULL));
+      UPB_ASSERT(!upb_inttable_lookupptr(from->ref2s, r, NULL));
       upb_inttable_insertptr2(from->ref2s, r, upb_value_ptr(NULL),
                               &upb_alloc_debugrefs);
     }
@@ -2973,15 +4536,15 @@ static void untrack(const upb_refcounted *r, const void *owner, bool ref2) {
   bool found;
   trackedref *ref;
 
-  assert(owner);
+  UPB_ASSERT(owner);
   if (owner == UPB_UNTRACKED_REF) return;
 
   upb_lock();
   found = upb_inttable_lookupptr(r->refs, owner, &v);
   /* This assert will fail if an owner attempts to release a ref it didn't have. */
-  UPB_ASSERT_VAR(found, found);
+  UPB_ASSERT(found);
   ref = upb_value_getptr(v);
-  assert(ref->is_ref2 == ref2);
+  UPB_ASSERT(ref->is_ref2 == ref2);
   if (--ref->count == 0) {
     free(ref);
     upb_inttable_removeptr(r->refs, owner, NULL);
@@ -2990,7 +4553,7 @@ static void untrack(const upb_refcounted *r, const void *owner, bool ref2) {
        * another refcounted object. */
       const upb_refcounted *from = owner;
       bool removed = upb_inttable_removeptr(from->ref2s, r, NULL);
-      assert(removed);
+      UPB_ASSERT(removed);
     }
   }
   upb_unlock();
@@ -3003,9 +4566,9 @@ static void checkref(const upb_refcounted *r, const void *owner, bool ref2) {
 
   upb_lock();
   found = upb_inttable_lookupptr(r->refs, owner, &v);
-  UPB_ASSERT_VAR(found, found);
+  UPB_ASSERT(found);
   ref = upb_value_getptr(v);
-  assert(ref->is_ref2 == ref2);
+  UPB_ASSERT(ref->is_ref2 == ref2);
   upb_unlock();
 }
 
@@ -3026,7 +4589,7 @@ static void getref2s(const upb_refcounted *owner, upb_inttable *tab) {
 
     /* To get the count we need to look in the target's table. */
     found = upb_inttable_lookupptr(to->refs, owner, &v);
-    assert(found);
+    UPB_ASSERT(found);
     ref = upb_value_getptr(v);
     count = upb_value_int32(ref->count);
 
@@ -3048,12 +4611,12 @@ static void visit_check(const upb_refcounted *obj, const upb_refcounted *subobj,
   bool removed;
   int32_t newcount;
 
-  assert(obj == s->obj);
-  assert(subobj);
+  UPB_ASSERT(obj == s->obj);
+  UPB_ASSERT(subobj);
   removed = upb_inttable_removeptr(ref2, subobj, &v);
   /* The following assertion will fail if the visit() function visits a subobj
    * that it did not have a ref2 on, or visits the same subobj too many times. */
-  assert(removed);
+  UPB_ASSERT(removed);
   newcount = upb_value_getint32(v) - 1;
   if (newcount > 0) {
     upb_inttable_insert2(ref2, (uintptr_t)subobj, upb_value_int32(newcount),
@@ -3075,7 +4638,7 @@ static void visit(const upb_refcounted *r, upb_refcounted_visit *v,
   if (r->vtbl->visit) r->vtbl->visit(r, visit_check, &state);
 
   /* This assertion will fail if the visit() function missed any children. */
-  assert(upb_inttable_count(&state.ref2) == 0);
+  UPB_ASSERT(upb_inttable_count(&state.ref2) == 0);
   upb_inttable_uninit2(&state.ref2, &upb_alloc_debugrefs);
   if (r->vtbl->visit) r->vtbl->visit(r, v, closure);
 }
@@ -3182,7 +4745,7 @@ static uint64_t trygetattr(const tarjan *t, const upb_refcounted *r) {
 static uint64_t getattr(const tarjan *t, const upb_refcounted *r) {
   upb_value v;
   bool found = upb_inttable_lookupptr(&t->objattr, r, &v);
-  UPB_ASSERT_VAR(found, found);
+  UPB_ASSERT(found);
   return upb_value_getuint64(v);
 }
 
@@ -3196,13 +4759,13 @@ static color_t color(tarjan *t, const upb_refcounted *r) {
 }
 
 static void set_gray(tarjan *t, const upb_refcounted *r) {
-  assert(color(t, r) == BLACK);
+  UPB_ASSERT(color(t, r) == BLACK);
   setattr(t, r, GRAY);
 }
 
 /* Pushes an obj onto the Tarjan stack and sets it to GREEN. */
 static void push(tarjan *t, const upb_refcounted *r) {
-  assert(color(t, r) == BLACK || color(t, r) == GRAY);
+  UPB_ASSERT(color(t, r) == BLACK || color(t, r) == GRAY);
   /* This defines the attr layout for the GREEN state.  "index" and "lowlink"
    * get 31 bits, which is plenty (limit of 2B objects frozen at a time). */
   setattr(t, r, GREEN | (t->index << 2) | (t->index << 33));
@@ -3217,7 +4780,7 @@ static void push(tarjan *t, const upb_refcounted *r) {
  * SCC group. */
 static upb_refcounted *pop(tarjan *t) {
   upb_refcounted *r = upb_value_getptr(upb_inttable_pop(&t->stack));
-  assert(color(t, r) == GREEN);
+  UPB_ASSERT(color(t, r) == GREEN);
   /* This defines the attr layout for nodes in the WHITE state.
    * Top of group stack is [group, NULL]; we point at group. */
   setattr(t, r, WHITE | (upb_inttable_count(&t->groups) - 2) << 8);
@@ -3237,7 +4800,7 @@ static void tarjan_newgroup(tarjan *t) {
 }
 
 static uint32_t idx(tarjan *t, const upb_refcounted *r) {
-  assert(color(t, r) == GREEN);
+  UPB_ASSERT(color(t, r) == GREEN);
   return (getattr(t, r) >> 2) & 0x7FFFFFFF;
 }
 
@@ -3250,7 +4813,7 @@ static uint32_t lowlink(tarjan *t, const upb_refcounted *r) {
 }
 
 static void set_lowlink(tarjan *t, const upb_refcounted *r, uint32_t lowlink) {
-  assert(color(t, r) == GREEN);
+  UPB_ASSERT(color(t, r) == GREEN);
   setattr(t, r, ((uint64_t)lowlink << 33) | (getattr(t, r) & 0x1FFFFFFFF));
 }
 
@@ -3259,10 +4822,10 @@ static uint32_t *group(tarjan *t, upb_refcounted *r) {
   upb_value v;
   bool found;
 
-  assert(color(t, r) == WHITE);
+  UPB_ASSERT(color(t, r) == WHITE);
   groupnum = getattr(t, r) >> 8;
   found = upb_inttable_lookup(&t->groups, groupnum, &v);
-  UPB_ASSERT_VAR(found, found);
+  UPB_ASSERT(found);
   return upb_value_getptr(v);
 }
 
@@ -3273,10 +4836,10 @@ static upb_refcounted *groupleader(tarjan *t, upb_refcounted *r) {
   upb_value v;
   bool found;
 
-  assert(color(t, r) == WHITE);
+  UPB_ASSERT(color(t, r) == WHITE);
   leader_slot = (getattr(t, r) >> 8) + 1;
   found = upb_inttable_lookup(&t->groups, leader_slot, &v);
-  UPB_ASSERT_VAR(found, found);
+  UPB_ASSERT(found);
   if (upb_value_getptr(v)) {
     return upb_value_getptr(v);
   } else {
@@ -3336,7 +4899,7 @@ static void do_tarjan(const upb_refcounted *obj, tarjan *t) {
 static void crossref(const upb_refcounted *r, const upb_refcounted *subobj,
                      void *_t) {
   tarjan *t = _t;
-  assert(color(t, r) > BLACK);
+  UPB_ASSERT(color(t, r) > BLACK);
   if (color(t, subobj) > BLACK && r->group != subobj->group) {
     /* Previously this ref was not reflected in subobj->group because they
      * were in the same group; now that they are split a ref must be taken. */
@@ -3404,13 +4967,13 @@ static bool freeze(upb_refcounted *const*roots, int n, upb_status *s,
       upb_refcounted *move = obj->next;
       if (obj == move) {
         /* Removing the last object from a group. */
-        assert(*obj->group == obj->individual_count);
+        UPB_ASSERT(*obj->group == obj->individual_count);
         upb_gfree(obj->group);
       } else {
         obj->next = move->next;
         /* This may decrease to zero; we'll collect GRAY objects (if any) that
          * remain in the group in the third pass. */
-        assert(*move->group >= move->individual_count);
+        UPB_ASSERT(*move->group >= move->individual_count);
         *move->group -= move->individual_count;
       }
 
@@ -3423,7 +4986,7 @@ static bool freeze(upb_refcounted *const*roots, int n, upb_status *s,
         *move->group = move->individual_count;
       } else {
         /* Group already has at least one object in it. */
-        assert(leader->group == group(&t, move));
+        UPB_ASSERT(leader->group == group(&t, move));
         move->group = group(&t, move);
         move->next = leader->next;
         leader->next = move;
@@ -3513,7 +5076,7 @@ static void merge(upb_refcounted *r, upb_refcounted *from) {
    * TODO(haberman): this linear algorithm can result in an overall O(n^2) bound
    * if the user continuously extends a group by one object.  Prevent this by
    * using one of the techniques in this paper:
-   *     ftp://www.ncedc.org/outgoing/geomorph/dino/orals/p245-tarjan.pdf */
+   *     http://bioinfo.ict.ac.cn/~dbu/AlgorithmCourses/Lectures/Union-Find-Tarjan.pdf */
   do { from->group = r->group; } while ((from = from->next) != base);
 
   /* Merge the two circularly linked lists by swapping their next pointers. */
@@ -3530,7 +5093,7 @@ static void release_ref2(const upb_refcounted *obj,
   UPB_UNUSED(closure);
   untrack(subobj, obj, true);
   if (!merged(obj, subobj)) {
-    assert(subobj->is_frozen);
+    UPB_ASSERT(subobj->is_frozen);
     unref(subobj);
   }
 }
@@ -3549,7 +5112,7 @@ static void unref(const upb_refcounted *r) {
     o = r;
     do {
       const upb_refcounted *next = o->next;
-      assert(o->is_frozen || o->individual_count == 0);
+      UPB_ASSERT(o->is_frozen || o->individual_count == 0);
       freeobj((upb_refcounted*)o);
       o = next;
     } while(o != r);
@@ -3573,9 +5136,9 @@ bool upb_refcounted_init(upb_refcounted *r,
    * basically every program using upb. */
   const int x = 1;
 #ifdef UPB_BIG_ENDIAN
-  assert(*(char*)&x != 1);
+  UPB_ASSERT(*(char*)&x != 1);
 #else
-  assert(*(char*)&x == 1);
+  UPB_ASSERT(*(char*)&x == 1);
 #endif
 #endif
 
@@ -3610,7 +5173,7 @@ void upb_refcounted_unref(const upb_refcounted *r, const void *owner) {
 }
 
 void upb_refcounted_ref2(const upb_refcounted *r, upb_refcounted *from) {
-  assert(!from->is_frozen);  /* Non-const pointer implies this. */
+  UPB_ASSERT(!from->is_frozen);  /* Non-const pointer implies this. */
   track(r, from, true);
   if (r->is_frozen) {
     refgroup(r->group);
@@ -3620,18 +5183,18 @@ void upb_refcounted_ref2(const upb_refcounted *r, upb_refcounted *from) {
 }
 
 void upb_refcounted_unref2(const upb_refcounted *r, upb_refcounted *from) {
-  assert(!from->is_frozen);  /* Non-const pointer implies this. */
+  UPB_ASSERT(!from->is_frozen);  /* Non-const pointer implies this. */
   untrack(r, from, true);
   if (r->is_frozen) {
     unref(r);
   } else {
-    assert(merged(r, from));
+    UPB_ASSERT(merged(r, from));
   }
 }
 
 void upb_refcounted_donateref(
     const upb_refcounted *r, const void *from, const void *to) {
-  assert(from != to);
+  UPB_ASSERT(from != to);
   if (to != NULL)
     upb_refcounted_ref(r, to);
   if (from != NULL)
@@ -3647,587 +5210,99 @@ bool upb_refcounted_freeze(upb_refcounted *const*roots, int n, upb_status *s,
   int i;
   bool ret;
   for (i = 0; i < n; i++) {
-    assert(!roots[i]->is_frozen);
+    UPB_ASSERT(!roots[i]->is_frozen);
   }
   ret = freeze(roots, n, s, maxdepth);
-  assert(!s || ret == upb_ok(s));
+  UPB_ASSERT(!s || ret == upb_ok(s));
   return ret;
 }
 
 
-/* Fallback implementation if the shim is not specialized by the JIT. */
-#define SHIM_WRITER(type, ctype)                                              \
-  bool upb_shim_set ## type (void *c, const void *hd, ctype val) {            \
-    uint8_t *m = c;                                                           \
-    const upb_shim_data *d = hd;                                              \
-    if (d->hasbit > 0)                                                        \
-      *(uint8_t*)&m[d->hasbit / 8] |= 1 << (d->hasbit % 8);                   \
-    *(ctype*)&m[d->offset] = val;                                             \
-    return true;                                                              \
-  }                                                                           \
-
-SHIM_WRITER(double, double)
-SHIM_WRITER(float,  float)
-SHIM_WRITER(int32,  int32_t)
-SHIM_WRITER(int64,  int64_t)
-SHIM_WRITER(uint32, uint32_t)
-SHIM_WRITER(uint64, uint64_t)
-SHIM_WRITER(bool,   bool)
-#undef SHIM_WRITER
-
-bool upb_shim_set(upb_handlers *h, const upb_fielddef *f, size_t offset,
-                  int32_t hasbit) {
-  upb_handlerattr attr = UPB_HANDLERATTR_INITIALIZER;
-  bool ok;
-
-  upb_shim_data *d = upb_gmalloc(sizeof(*d));
-  if (!d) return false;
-  d->offset = offset;
-  d->hasbit = hasbit;
-
-  upb_handlerattr_sethandlerdata(&attr, d);
-  upb_handlerattr_setalwaysok(&attr, true);
-  upb_handlers_addcleanup(h, d, upb_gfree);
-
-#define TYPE(u, l) \
-  case UPB_TYPE_##u: \
-    ok = upb_handlers_set##l(h, f, upb_shim_set##l, &attr); break;
-
-  ok = false;
-
-  switch (upb_fielddef_type(f)) {
-    TYPE(INT64,  int64);
-    TYPE(INT32,  int32);
-    TYPE(ENUM,   int32);
-    TYPE(UINT64, uint64);
-    TYPE(UINT32, uint32);
-    TYPE(DOUBLE, double);
-    TYPE(FLOAT,  float);
-    TYPE(BOOL,   bool);
-    default: assert(false); break;
-  }
-#undef TYPE
-
-  upb_handlerattr_uninit(&attr);
-  return ok;
-}
-
-const upb_shim_data *upb_shim_getdata(const upb_handlers *h, upb_selector_t s,
-                                      upb_fieldtype_t *type) {
-  upb_func *f = upb_handlers_gethandler(h, s);
-
-  if ((upb_int64_handlerfunc*)f == upb_shim_setint64) {
-    *type = UPB_TYPE_INT64;
-  } else if ((upb_int32_handlerfunc*)f == upb_shim_setint32) {
-    *type = UPB_TYPE_INT32;
-  } else if ((upb_uint64_handlerfunc*)f == upb_shim_setuint64) {
-    *type = UPB_TYPE_UINT64;
-  } else if ((upb_uint32_handlerfunc*)f == upb_shim_setuint32) {
-    *type = UPB_TYPE_UINT32;
-  } else if ((upb_double_handlerfunc*)f == upb_shim_setdouble) {
-    *type = UPB_TYPE_DOUBLE;
-  } else if ((upb_float_handlerfunc*)f == upb_shim_setfloat) {
-    *type = UPB_TYPE_FLOAT;
-  } else if ((upb_bool_handlerfunc*)f == upb_shim_setbool) {
-    *type = UPB_TYPE_BOOL;
-  } else {
-    return NULL;
-  }
-
-  return (const upb_shim_data*)upb_handlers_gethandlerdata(h, s);
-}
-
-
-#include <string.h>
-
-static void upb_symtab_free(upb_refcounted *r) {
-  upb_symtab *s = (upb_symtab*)r;
-  upb_strtable_iter i;
-  upb_strtable_begin(&i, &s->symtab);
-  for (; !upb_strtable_done(&i); upb_strtable_next(&i)) {
-    const upb_def *def = upb_value_getptr(upb_strtable_iter_value(&i));
-    upb_def_unref(def, s);
+bool upb_bufsrc_putbuf(const char *buf, size_t len, upb_bytessink *sink) {
+  void *subc;
+  bool ret;
+  upb_bufhandle handle;
+  upb_bufhandle_init(&handle);
+  upb_bufhandle_setbuf(&handle, buf, 0);
+  ret = upb_bytessink_start(sink, len, &subc);
+  if (ret && len != 0) {
+    ret = (upb_bytessink_putbuf(sink, subc, buf, len, &handle) >= len);
   }
-  upb_strtable_uninit(&s->symtab);
-  upb_gfree(s);
-}
-
-upb_symtab *upb_symtab_new(const void *owner) {
-  static const struct upb_refcounted_vtbl vtbl = {NULL, &upb_symtab_free};
-
-  upb_symtab *s = upb_gmalloc(sizeof(*s));
-  if (!s) {
-    return NULL;
+  if (ret) {
+    ret = upb_bytessink_end(sink);
   }
-
-  upb_refcounted_init(upb_symtab_upcast_mutable(s), &vtbl, owner);
-  upb_strtable_init(&s->symtab, UPB_CTYPE_PTR);
-  return s;
-}
-
-void upb_symtab_freeze(upb_symtab *s) {
-  upb_refcounted *r;
-  bool ok;
-
-  assert(!upb_symtab_isfrozen(s));
-  r = upb_symtab_upcast_mutable(s);
-  /* The symtab does not take ref2's (see refcounted.h) on the defs, because
-   * defs cannot refer back to the table and therefore cannot create cycles.  So
-   * 0 will suffice for maxdepth here. */
-  ok = upb_refcounted_freeze(&r, 1, NULL, 0);
-  UPB_ASSERT_VAR(ok, ok);
-}
-
-const upb_def *upb_symtab_lookup(const upb_symtab *s, const char *sym) {
-  upb_value v;
-  upb_def *ret = upb_strtable_lookup(&s->symtab, sym, &v) ?
-      upb_value_getptr(v) : NULL;
+  upb_bufhandle_uninit(&handle);
   return ret;
 }
 
-const upb_msgdef *upb_symtab_lookupmsg(const upb_symtab *s, const char *sym) {
-  upb_value v;
-  upb_def *def = upb_strtable_lookup(&s->symtab, sym, &v) ?
-      upb_value_getptr(v) : NULL;
-  return def ? upb_dyncast_msgdef(def) : NULL;
-}
-
-const upb_enumdef *upb_symtab_lookupenum(const upb_symtab *s, const char *sym) {
-  upb_value v;
-  upb_def *def = upb_strtable_lookup(&s->symtab, sym, &v) ?
-      upb_value_getptr(v) : NULL;
-  return def ? upb_dyncast_enumdef(def) : NULL;
-}
-
-/* Given a symbol and the base symbol inside which it is defined, find the
- * symbol's definition in t. */
-static upb_def *upb_resolvename(const upb_strtable *t,
-                                const char *base, const char *sym) {
-  if(strlen(sym) == 0) return NULL;
-  if(sym[0] == '.') {
-    /* Symbols starting with '.' are absolute, so we do a single lookup.
-     * Slice to omit the leading '.' */
-    upb_value v;
-    return upb_strtable_lookup(t, sym + 1, &v) ? upb_value_getptr(v) : NULL;
-  } else {
-    /* Remove components from base until we find an entry or run out.
-     * TODO: This branch is totally broken, but currently not used. */
-    (void)base;
-    assert(false);
-    return NULL;
-  }
-}
-
-const upb_def *upb_symtab_resolve(const upb_symtab *s, const char *base,
-                                  const char *sym) {
-  upb_def *ret = upb_resolvename(&s->symtab, base, sym);
-  return ret;
-}
-
-/* Starts a depth-first traversal at "def", recursing into any subdefs
- * (ie. submessage types).  Adds duplicates of existing defs to addtab
- * wherever necessary, so that the resulting symtab will be consistent once
- * addtab is added.
- *
- * More specifically, if any def D is found in the DFS that:
- *
- *   1. can reach a def that is being replaced by something in addtab, AND
- *
- *   2. is not itself being replaced already (ie. this name doesn't already
- *      exist in addtab)
- *
- * ...then a duplicate (new copy) of D will be added to addtab.
- *
- * Returns true if this happened for any def reachable from "def."
- *
- * It is slightly tricky to do this correctly in the presence of cycles.  If we
- * detect that our DFS has hit a cycle, we might not yet know if any SCCs on
- * our stack can reach a def in addtab or not.  Once we figure this out, that
- * answer needs to apply to *all* defs in these SCCs, even if we visited them
- * already.  So a straight up one-pass cycle-detecting DFS won't work.
- *
- * To work around this problem, we traverse each SCC (which we already
- * computed, since these defs are frozen) as a single node.  We first compute
- * whether the SCC as a whole can reach any def in addtab, then we dup (or not)
- * the entire SCC.  This requires breaking the encapsulation of upb_refcounted,
- * since that is where we get the data about what SCC we are in. */
-static bool upb_resolve_dfs(const upb_def *def, upb_strtable *addtab,
-                            const void *new_owner, upb_inttable *seen,
-                            upb_status *s) {
-  upb_value v;
-  bool need_dup;
-  const upb_def *base;
-  const void* memoize_key;
-
-  /* Memoize results of this function for efficiency (since we're traversing a
-   * DAG this is not needed to limit the depth of the search).
-   *
-   * We memoize by SCC instead of by individual def. */
-  memoize_key = def->base.group;
-
-  if (upb_inttable_lookupptr(seen, memoize_key, &v))
-    return upb_value_getbool(v);
-
-  /* Visit submessages for all messages in the SCC. */
-  need_dup = false;
-  base = def;
-  do {
-    upb_value v;
-    const upb_msgdef *m;
-
-    assert(upb_def_isfrozen(def));
-    if (def->type == UPB_DEF_FIELD) continue;
-    if (upb_strtable_lookup(addtab, upb_def_fullname(def), &v)) {
-      need_dup = true;
-    }
-
-    /* For messages, continue the recursion by visiting all subdefs, but only
-     * ones in different SCCs. */
-    m = upb_dyncast_msgdef(def);
-    if (m) {
-      upb_msg_field_iter i;
-      for(upb_msg_field_begin(&i, m);
-          !upb_msg_field_done(&i);
-          upb_msg_field_next(&i)) {
-        upb_fielddef *f = upb_msg_iter_field(&i);
-        const upb_def *subdef;
-
-        if (!upb_fielddef_hassubdef(f)) continue;
-        subdef = upb_fielddef_subdef(f);
-
-        /* Skip subdefs in this SCC. */
-        if (def->base.group == subdef->base.group) continue;
-
-        /* |= to avoid short-circuit; we need its side-effects. */
-        need_dup |= upb_resolve_dfs(subdef, addtab, new_owner, seen, s);
-        if (!upb_ok(s)) return false;
-      }
-    }
-  } while ((def = (upb_def*)def->base.next) != base);
-
-  if (need_dup) {
-    /* Dup all defs in this SCC that don't already have entries in addtab. */
-    def = base;
-    do {
-      const char *name;
-
-      if (def->type == UPB_DEF_FIELD) continue;
-      name = upb_def_fullname(def);
-      if (!upb_strtable_lookup(addtab, name, NULL)) {
-        upb_def *newdef = upb_def_dup(def, new_owner);
-        if (!newdef) goto oom;
-        newdef->came_from_user = false;
-        if (!upb_strtable_insert(addtab, name, upb_value_ptr(newdef)))
-          goto oom;
-      }
-    } while ((def = (upb_def*)def->base.next) != base);
-  }
-
-  upb_inttable_insertptr(seen, memoize_key, upb_value_bool(need_dup));
-  return need_dup;
-
-oom:
-  upb_status_seterrmsg(s, "out of memory");
-  return false;
-}
-
-/* TODO(haberman): we need a lot more testing of error conditions.
- * The came_from_user stuff in particular is not tested. */
-static bool symtab_add(upb_symtab *s, upb_def *const*defs, size_t n,
-                       void *ref_donor, upb_refcounted *freeze_also,
-                       upb_status *status) {
-  size_t i;
-  size_t add_n;
-  size_t freeze_n;
-  upb_strtable_iter iter;
-  upb_refcounted **add_objs = NULL;
-  upb_def **add_defs = NULL;
-  size_t add_objs_size;
-  upb_strtable addtab;
-  upb_inttable seen;
-
-  if (n == 0 && !freeze_also) {
-    return true;
-  }
-
-  assert(!upb_symtab_isfrozen(s));
-  if (!upb_strtable_init(&addtab, UPB_CTYPE_PTR)) {
-    upb_status_seterrmsg(status, "out of memory");
-    return false;
-  }
-
-  /* Add new defs to our "add" set. */
-  for (i = 0; i < n; i++) {
-    upb_def *def = defs[i];
-    const char *fullname;
-    upb_fielddef *f;
-
-    if (upb_def_isfrozen(def)) {
-      upb_status_seterrmsg(status, "added defs must be mutable");
-      goto err;
-    }
-    assert(!upb_def_isfrozen(def));
-    fullname = upb_def_fullname(def);
-    if (!fullname) {
-      upb_status_seterrmsg(
-          status, "Anonymous defs cannot be added to a symtab");
-      goto err;
-    }
-
-    f = upb_dyncast_fielddef_mutable(def);
-
-    if (f) {
-      if (!upb_fielddef_containingtypename(f)) {
-        upb_status_seterrmsg(status,
-                             "Standalone fielddefs must have a containing type "
-                             "(extendee) name set");
-        goto err;
-      }
-    } else {
-      if (upb_strtable_lookup(&addtab, fullname, NULL)) {
-        upb_status_seterrf(status, "Conflicting defs named '%s'", fullname);
-        goto err;
-      }
-      /* We need this to back out properly, because if there is a failure we
-       * need to donate the ref back to the caller. */
-      def->came_from_user = true;
-      upb_def_donateref(def, ref_donor, s);
-      if (!upb_strtable_insert(&addtab, fullname, upb_value_ptr(def)))
-        goto oom_err;
-    }
-  }
-
-  /* Add standalone fielddefs (ie. extensions) to the appropriate messages.
-   * If the appropriate message only exists in the existing symtab, duplicate
-   * it so we have a mutable copy we can add the fields to. */
-  for (i = 0; i < n; i++) {
-    upb_def *def = defs[i];
-    upb_fielddef *f = upb_dyncast_fielddef_mutable(def);
-    const char *msgname;
-    upb_value v;
-    upb_msgdef *m;
-
-    if (!f) continue;
-    msgname = upb_fielddef_containingtypename(f);
-    /* We validated this earlier in this function. */
-    assert(msgname);
-
-    /* If the extendee name is absolutely qualified, move past the initial ".".
-     * TODO(haberman): it is not obvious what it would mean if this was not
-     * absolutely qualified. */
-    if (msgname[0] == '.') {
-      msgname++;
-    }
-
-    if (upb_strtable_lookup(&addtab, msgname, &v)) {
-      /* Extendee is in the set of defs the user asked us to add. */
-      m = upb_value_getptr(v);
-    } else {
-      /* Need to find and dup the extendee from the existing symtab. */
-      const upb_msgdef *frozen_m = upb_symtab_lookupmsg(s, msgname);
-      if (!frozen_m) {
-        upb_status_seterrf(status,
-                           "Tried to extend message %s that does not exist "
-                           "in this SymbolTable.",
-                           msgname);
-        goto err;
-      }
-      m = upb_msgdef_dup(frozen_m, s);
-      if (!m) goto oom_err;
-      if (!upb_strtable_insert(&addtab, msgname, upb_value_ptr(m))) {
-        upb_msgdef_unref(m, s);
-        goto oom_err;
-      }
-    }
-
-    if (!upb_msgdef_addfield(m, f, ref_donor, status)) {
-      goto err;
-    }
-  }
-
-  /* Add dups of any existing def that can reach a def with the same name as
-   * anything in our "add" set. */
-  if (!upb_inttable_init(&seen, UPB_CTYPE_BOOL)) goto oom_err;
-  upb_strtable_begin(&iter, &s->symtab);
-  for (; !upb_strtable_done(&iter); upb_strtable_next(&iter)) {
-    upb_def *def = upb_value_getptr(upb_strtable_iter_value(&iter));
-    upb_resolve_dfs(def, &addtab, s, &seen, status);
-    if (!upb_ok(status)) goto err;
-  }
-  upb_inttable_uninit(&seen);
-
-  /* Now using the table, resolve symbolic references for subdefs. */
-  upb_strtable_begin(&iter, &addtab);
-  for (; !upb_strtable_done(&iter); upb_strtable_next(&iter)) {
-    const char *base;
-    upb_def *def = upb_value_getptr(upb_strtable_iter_value(&iter));
-    upb_msgdef *m = upb_dyncast_msgdef_mutable(def);
-    upb_msg_field_iter j;
-
-    if (!m) continue;
-    /* Type names are resolved relative to the message in which they appear. */
-    base = upb_msgdef_fullname(m);
-
-    for(upb_msg_field_begin(&j, m);
-        !upb_msg_field_done(&j);
-        upb_msg_field_next(&j)) {
-      upb_fielddef *f = upb_msg_iter_field(&j);
-      const char *name = upb_fielddef_subdefname(f);
-      if (name && !upb_fielddef_subdef(f)) {
-        /* Try the lookup in the current set of to-be-added defs first. If not
-         * there, try existing defs. */
-        upb_def *subdef = upb_resolvename(&addtab, base, name);
-        if (subdef == NULL) {
-          subdef = upb_resolvename(&s->symtab, base, name);
-        }
-        if (subdef == NULL) {
-          upb_status_seterrf(
-              status, "couldn't resolve name '%s' in message '%s'", name, base);
-          goto err;
-        } else if (!upb_fielddef_setsubdef(f, subdef, status)) {
-          goto err;
-        }
-      }
-    }
-  }
-
-  /* We need an array of the defs in addtab, for passing to
-   * upb_refcounted_freeze(). */
-  add_objs_size = upb_strtable_count(&addtab);
-  if (freeze_also) {
-    add_objs_size++;
-  }
-
-  add_defs = upb_gmalloc(sizeof(void*) * add_objs_size);
-  if (add_defs == NULL) goto oom_err;
-  upb_strtable_begin(&iter, &addtab);
-  for (add_n = 0; !upb_strtable_done(&iter); upb_strtable_next(&iter)) {
-    add_defs[add_n++] = upb_value_getptr(upb_strtable_iter_value(&iter));
-  }
-
-  /* Validate defs. */
-  if (!_upb_def_validate(add_defs, add_n, status)) {
-    goto err;
-  }
-
-  /* Cheat a little and give the array a new type.
-   * This is probably undefined behavior, but this code will be deleted soon. */
-  add_objs = (upb_refcounted**)add_defs;
-
-  freeze_n = add_n;
-  if (freeze_also) {
-    add_objs[freeze_n++] = freeze_also;
-  }
-
-  if (!upb_refcounted_freeze(add_objs, freeze_n, status,
-                             UPB_MAX_MESSAGE_DEPTH * 2)) {
-    goto err;
-  }
-
-  /* This must be delayed until all errors have been detected, since error
-   * recovery code uses this table to cleanup defs. */
-  upb_strtable_uninit(&addtab);
-
-  /* TODO(haberman) we don't properly handle errors after this point (like
-   * OOM in upb_strtable_insert() below). */
-  for (i = 0; i < add_n; i++) {
-    upb_def *def = (upb_def*)add_objs[i];
-    const char *name = upb_def_fullname(def);
-    upb_value v;
-    bool success;
-
-    if (upb_strtable_remove(&s->symtab, name, &v)) {
-      const upb_def *def = upb_value_getptr(v);
-      upb_def_unref(def, s);
-    }
-    success = upb_strtable_insert(&s->symtab, name, upb_value_ptr(def));
-    UPB_ASSERT_VAR(success, success == true);
-  }
-  upb_gfree(add_defs);
-  return true;
-
-oom_err:
-  upb_status_seterrmsg(status, "out of memory");
-err: {
-    /* For defs the user passed in, we need to donate the refs back.  For defs
-     * we dup'd, we need to just unref them. */
-    upb_strtable_begin(&iter, &addtab);
-    for (; !upb_strtable_done(&iter); upb_strtable_next(&iter)) {
-      upb_def *def = upb_value_getptr(upb_strtable_iter_value(&iter));
-      bool came_from_user = def->came_from_user;
-      def->came_from_user = false;
-      if (came_from_user) {
-        upb_def_donateref(def, s, ref_donor);
-      } else {
-        upb_def_unref(def, s);
-      }
-    }
-  }
-  upb_strtable_uninit(&addtab);
-  upb_gfree(add_defs);
-  assert(!upb_ok(status));
-  return false;
-}
+struct upb_bufsink {
+  upb_byteshandler handler;
+  upb_bytessink sink;
+  upb_env *env;
+  char *ptr;
+  size_t len, size;
+};
 
-bool upb_symtab_add(upb_symtab *s, upb_def *const*defs, size_t n,
-                    void *ref_donor, upb_status *status) {
-  return symtab_add(s, defs, n, ref_donor, NULL, status);
+static void *upb_bufsink_start(void *_sink, const void *hd, size_t size_hint) {
+  upb_bufsink *sink = _sink;
+  UPB_UNUSED(hd);
+  UPB_UNUSED(size_hint);
+  sink->len = 0;
+  return sink;
 }
 
-bool upb_symtab_addfile(upb_symtab *s, upb_filedef *file, upb_status *status) {
-  size_t n;
-  size_t i;
-  upb_def **defs;
-  bool ret;
+static size_t upb_bufsink_string(void *_sink, const void *hd, const char *ptr,
+                                size_t len, const upb_bufhandle *handle) {
+  upb_bufsink *sink = _sink;
+  size_t new_size = sink->size;
 
-  n = upb_filedef_defcount(file);
-  defs = upb_gmalloc(sizeof(*defs) * n);
+  UPB_ASSERT(new_size > 0);
+  UPB_UNUSED(hd);
+  UPB_UNUSED(handle);
 
-  if (defs == NULL) {
-    upb_status_seterrmsg(status, "Out of memory");
-    return false;
+  while (sink->len + len > new_size) {
+    new_size *= 2;
   }
 
-  for (i = 0; i < n; i++) {
-    defs[i] = upb_filedef_mutabledef(file, i);
+  if (new_size != sink->size) {
+    sink->ptr = upb_env_realloc(sink->env, sink->ptr, sink->size, new_size);
+    sink->size = new_size;
   }
 
-  ret = symtab_add(s, defs, n, NULL, upb_filedef_upcast_mutable(file), status);
+  memcpy(sink->ptr + sink->len, ptr, len);
+  sink->len += len;
 
-  upb_gfree(defs);
-  return ret;
+  return len;
 }
 
-/* Iteration. */
+upb_bufsink *upb_bufsink_new(upb_env *env) {
+  upb_bufsink *sink = upb_env_malloc(env, sizeof(upb_bufsink));
+  upb_byteshandler_init(&sink->handler);
+  upb_byteshandler_setstartstr(&sink->handler, upb_bufsink_start, NULL);
+  upb_byteshandler_setstring(&sink->handler, upb_bufsink_string, NULL);
 
-static void advance_to_matching(upb_symtab_iter *iter) {
-  if (iter->type == UPB_DEF_ANY)
-    return;
+  upb_bytessink_reset(&sink->sink, &sink->handler, sink);
 
-  while (!upb_strtable_done(&iter->iter) &&
-         iter->type != upb_symtab_iter_def(iter)->type) {
-    upb_strtable_next(&iter->iter);
-  }
-}
+  sink->env = env;
+  sink->size = 32;
+  sink->ptr = upb_env_malloc(env, sink->size);
+  sink->len = 0;
 
-void upb_symtab_begin(upb_symtab_iter *iter, const upb_symtab *s,
-                      upb_deftype_t type) {
-  upb_strtable_begin(&iter->iter, &s->symtab);
-  iter->type = type;
-  advance_to_matching(iter);
+  return sink;
 }
 
-void upb_symtab_next(upb_symtab_iter *iter) {
-  upb_strtable_next(&iter->iter);
-  advance_to_matching(iter);
+void upb_bufsink_free(upb_bufsink *sink) {
+  upb_env_free(sink->env, sink->ptr);
+  upb_env_free(sink->env, sink);
 }
 
-bool upb_symtab_done(const upb_symtab_iter *iter) {
-  return upb_strtable_done(&iter->iter);
+upb_bytessink *upb_bufsink_sink(upb_bufsink *sink) {
+  return &sink->sink;
 }
 
-const upb_def *upb_symtab_iter_def(const upb_symtab_iter *iter) {
-  return upb_value_getptr(upb_strtable_iter_value(&iter->iter));
+const char *upb_bufsink_getdata(const upb_bufsink *sink, size_t *len) {
+  *len = sink->len;
+  return sink->ptr;
 }
 /*
 ** upb_table Implementation
@@ -4244,16 +5319,11 @@ const upb_def *upb_symtab_iter_def(const upb_symtab_iter *iter) {
 #define ARRAY_SIZE(x) \
     ((sizeof(x)/sizeof(0[x])) / ((size_t)(!(sizeof(x) % sizeof(0[x])))))
 
-#ifdef NDEBUG
 static void upb_check_alloc(upb_table *t, upb_alloc *a) {
   UPB_UNUSED(t);
   UPB_UNUSED(a);
+  UPB_ASSERT_DEBUGVAR(t->alloc == a);
 }
-#else
-static void upb_check_alloc(upb_table *t, upb_alloc *a) {
-  assert(t->alloc == a);
-}
-#endif
 
 static const double MAX_LOAD = 0.85;
 
@@ -4362,7 +5432,7 @@ static void uninit(upb_table *t, upb_alloc *a) {
 
 static upb_tabent *emptyent(upb_table *t) {
   upb_tabent *e = mutable_entries(t) + upb_table_size(t);
-  while (1) { if (upb_tabent_isempty(--e)) return e; assert(e > t->entries); }
+  while (1) { if (upb_tabent_isempty(--e)) return e; UPB_ASSERT(e > t->entries); }
 }
 
 static upb_tabent *getentry_mutable(upb_table *t, uint32_t hash) {
@@ -4407,10 +5477,8 @@ static void insert(upb_table *t, lookupkey_t key, upb_tabkey tabkey,
   upb_tabent *mainpos_e;
   upb_tabent *our_e;
 
-  UPB_UNUSED(eql);
-  UPB_UNUSED(key);
-  assert(findentry(t, key, hash, eql) == NULL);
-  assert(val.ctype == t->ctype);
+  UPB_ASSERT(findentry(t, key, hash, eql) == NULL);
+  UPB_ASSERT_DEBUGVAR(val.ctype == t->ctype);
 
   t->count++;
   mainpos_e = getentry_mutable(t, hash);
@@ -4437,7 +5505,7 @@ static void insert(upb_table *t, lookupkey_t key, upb_tabkey tabkey,
       *new_e = *mainpos_e;  /* copies next. */
       while (chain->next != mainpos_e) {
         chain = (upb_tabent*)chain->next;
-        assert(chain);
+        UPB_ASSERT(chain);
       }
       chain->next = new_e;
       our_e = mainpos_e;
@@ -4446,7 +5514,7 @@ static void insert(upb_table *t, lookupkey_t key, upb_tabkey tabkey,
   }
   our_e->key = tabkey;
   our_e->val.val = val.val;
-  assert(findentry(t, key, hash, eql) == our_e);
+  UPB_ASSERT(findentry(t, key, hash, eql) == our_e);
 }
 
 static bool rm(upb_table *t, lookupkey_t key, upb_value *val,
@@ -4456,38 +5524,33 @@ static bool rm(upb_table *t, lookupkey_t key, upb_value *val,
   if (eql(chain->key, key)) {
     /* Element to remove is at the head of its chain. */
     t->count--;
-    if (val) {
-      _upb_value_setval(val, chain->val.val, t->ctype);
-    }
+    if (val) _upb_value_setval(val, chain->val.val, t->ctype);
+    if (removed) *removed = chain->key;
     if (chain->next) {
       upb_tabent *move = (upb_tabent*)chain->next;
       *chain = *move;
-      if (removed) *removed = move->key;
       move->key = 0;  /* Make the slot empty. */
     } else {
-      if (removed) *removed = chain->key;
       chain->key = 0;  /* Make the slot empty. */
     }
     return true;
   } else {
     /* Element to remove is either in a non-head position or not in the
      * table. */
-    while (chain->next && !eql(chain->next->key, key))
+    while (chain->next && !eql(chain->next->key, key)) {
       chain = (upb_tabent*)chain->next;
+    }
     if (chain->next) {
       /* Found element to remove. */
-      upb_tabent *rm;
-
-      if (val) {
-        _upb_value_setval(val, chain->next->val.val, t->ctype);
-      }
-      rm = (upb_tabent*)chain->next;
+      upb_tabent *rm = (upb_tabent*)chain->next;
+      t->count--;
+      if (val) _upb_value_setval(val, chain->next->val.val, t->ctype);
       if (removed) *removed = rm->key;
-      rm->key = 0;
+      rm->key = 0;  /* Make the slot empty. */
       chain->next = rm->next;
-      t->count--;
       return true;
     } else {
+      /* Element to remove is not in the table. */
       return false;
     }
   }
@@ -4596,7 +5659,7 @@ bool upb_strtable_lookup2(const upb_strtable *t, const char *key, size_t len,
 
 bool upb_strtable_remove3(upb_strtable *t, const char *key, size_t len,
                          upb_value *val, upb_alloc *alloc) {
-  uint32_t hash = MurmurHash2(key, strlen(key), 0);
+  uint32_t hash = MurmurHash2(key, len, 0);
   upb_tabkey tabkey;
   if (rm(&t->t, strkey2(key, len), val, &tabkey, hash, &streql)) {
     upb_free(alloc, (void*)tabkey);
@@ -4627,19 +5690,19 @@ bool upb_strtable_done(const upb_strtable_iter *i) {
 }
 
 const char *upb_strtable_iter_key(const upb_strtable_iter *i) {
-  assert(!upb_strtable_done(i));
+  UPB_ASSERT(!upb_strtable_done(i));
   return upb_tabstr(str_tabent(i)->key, NULL);
 }
 
 size_t upb_strtable_iter_keylength(const upb_strtable_iter *i) {
   uint32_t len;
-  assert(!upb_strtable_done(i));
+  UPB_ASSERT(!upb_strtable_done(i));
   upb_tabstr(str_tabent(i)->key, &len);
   return len;
 }
 
 upb_value upb_strtable_iter_value(const upb_strtable_iter *i) {
-  assert(!upb_strtable_done(i));
+  UPB_ASSERT(!upb_strtable_done(i));
   return _upb_value_val(str_tabent(i)->val.val, i->t->t.ctype);
 }
 
@@ -4698,9 +5761,9 @@ static void check(upb_inttable *t) {
     upb_inttable_iter i;
     upb_inttable_begin(&i, t);
     for(; !upb_inttable_done(&i); upb_inttable_next(&i), count++) {
-      assert(upb_inttable_lookup(t, upb_inttable_iter_key(&i), NULL));
+      UPB_ASSERT(upb_inttable_lookup(t, upb_inttable_iter_key(&i), NULL));
     }
-    assert(count == upb_inttable_count(t));
+    UPB_ASSERT(count == upb_inttable_count(t));
   }
 #endif
 }
@@ -4738,13 +5801,12 @@ bool upb_inttable_insert2(upb_inttable *t, uintptr_t key, upb_value val,
                           upb_alloc *a) {
   upb_tabval tabval;
   tabval.val = val.val;
-  UPB_UNUSED(tabval);
-  assert(upb_arrhas(tabval));  /* This will reject (uint64_t)-1.  Fix this. */
+  UPB_ASSERT(upb_arrhas(tabval));  /* This will reject (uint64_t)-1.  Fix this. */
 
   upb_check_alloc(&t->t, a);
 
   if (key < t->array_size) {
-    assert(!upb_arrhas(t->array[key]));
+    UPB_ASSERT(!upb_arrhas(t->array[key]));
     t->array_count++;
     mutable_array(t)[key].val = val.val;
   } else {
@@ -4767,7 +5829,7 @@ bool upb_inttable_insert2(upb_inttable *t, uintptr_t key, upb_value val,
         insert(&new_table, intkey(e->key), e->key, v, hash, &inthash, &inteql);
       }
 
-      assert(t->t.count == new_table.count);
+      UPB_ASSERT(t->t.count == new_table.count);
 
       uninit(&t->t, a);
       t->t = new_table;
@@ -4807,9 +5869,7 @@ bool upb_inttable_remove(upb_inttable *t, uintptr_t key, upb_value *val) {
       success = false;
     }
   } else {
-    upb_tabkey removed;
-    uint32_t hash = upb_inthash(key);
-    success = rm(&t->t, intkey(key), val, &removed, hash, &inteql);
+    success = rm(&t->t, intkey(key), val, NULL, upb_inthash(key), &inteql);
   }
   check(t);
   return success;
@@ -4823,7 +5883,7 @@ bool upb_inttable_push2(upb_inttable *t, upb_value val, upb_alloc *a) {
 upb_value upb_inttable_pop(upb_inttable *t) {
   upb_value val;
   bool ok = upb_inttable_remove(t, upb_inttable_count(t) - 1, &val);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return val;
 }
 
@@ -4879,7 +5939,7 @@ void upb_inttable_compact2(upb_inttable *t, upb_alloc *a) {
     arr_count -= counts[size_lg2];
   }
 
-  assert(arr_count <= upb_inttable_count(t));
+  UPB_ASSERT(arr_count <= upb_inttable_count(t));
 
   {
     /* Insert all elements into new, perfectly-sized table. */
@@ -4894,8 +5954,8 @@ void upb_inttable_compact2(upb_inttable *t, upb_alloc *a) {
       uintptr_t k = upb_inttable_iter_key(&i);
       upb_inttable_insert2(&new_t, k, upb_inttable_iter_value(&i), a);
     }
-    assert(new_t.array_size == arr_size);
-    assert(new_t.t.size_lg2 == hashsize_lg2);
+    UPB_ASSERT(new_t.array_size == arr_size);
+    UPB_ASSERT(new_t.t.size_lg2 == hashsize_lg2);
   }
   upb_inttable_uninit2(t, a);
   *t = new_t;
@@ -4904,12 +5964,12 @@ void upb_inttable_compact2(upb_inttable *t, upb_alloc *a) {
 /* Iteration. */
 
 static const upb_tabent *int_tabent(const upb_inttable_iter *i) {
-  assert(!i->array_part);
+  UPB_ASSERT(!i->array_part);
   return &i->t->t.entries[i->index];
 }
 
 static upb_tabval int_arrent(const upb_inttable_iter *i) {
-  assert(i->array_part);
+  UPB_ASSERT(i->array_part);
   return i->t->array[i->index];
 }
 
@@ -4946,12 +6006,12 @@ bool upb_inttable_done(const upb_inttable_iter *i) {
 }
 
 uintptr_t upb_inttable_iter_key(const upb_inttable_iter *i) {
-  assert(!upb_inttable_done(i));
+  UPB_ASSERT(!upb_inttable_done(i));
   return i->array_part ? i->index : int_tabent(i)->key;
 }
 
 upb_value upb_inttable_iter_value(const upb_inttable_iter *i) {
-  assert(!upb_inttable_done(i));
+  UPB_ASSERT(!upb_inttable_done(i));
   return _upb_value_val(
       i->array_part ? i->t->array[i->index].val : int_tabent(i)->val.val,
       i->t->t.ctype);
@@ -5169,7 +6229,7 @@ bool upb_dumptostderr(void *closure, const upb_status* status) {
 static void nullz(upb_status *status) {
   const char *ellipsis = "...";
   size_t len = strlen(ellipsis);
-  assert(sizeof(status->msg) > len);
+  UPB_ASSERT(sizeof(status->msg) > len);
   memcpy(status->msg + sizeof(status->msg) - len, ellipsis, len);
 }
 
@@ -5252,7 +6312,7 @@ upb_alloc upb_alloc_global = {&upb_global_allocfunc};
 /* Be conservative and choose 16 in case anyone is using SSE. */
 static const size_t maxalign = 16;
 
-static size_t align_up(size_t size) {
+static size_t align_up_max(size_t size) {
   return ((size + maxalign - 1) / maxalign) * maxalign;
 }
 
@@ -5276,7 +6336,7 @@ static void upb_arena_addblock(upb_arena *a, void *ptr, size_t size,
 
   block->next = a->block_head;
   block->size = size;
-  block->used = align_up(sizeof(mem_block));
+  block->used = align_up_max(sizeof(mem_block));
   block->owned = owned;
 
   a->block_head = block;
@@ -5309,7 +6369,7 @@ static void *upb_arena_doalloc(upb_alloc *alloc, void *ptr, size_t oldsize,
     return NULL;  /* We are an arena, don't need individual frees. */
   }
 
-  size = align_up(size);
+  size = align_up_max(size);
 
   /* TODO(haberman): special-case if this is a realloc of the last alloc? */
 
@@ -5379,6 +6439,10 @@ void upb_arena_uninit(upb_arena *a) {
 
     block = next;
   }
+
+  /* Protect against multiple-uninit. */
+  a->cleanup_head = NULL;
+  a->block_head = NULL;
 }
 
 bool upb_arena_addcleanup(upb_arena *a, upb_cleanup_func *func, void *ud) {
@@ -5479,8 +6543,6 @@ size_t upb_env_bytesallocated(const upb_env *e) {
  * Do not edit -- your changes will be discarded when the file is
  * regenerated. */
 
-#include <assert.h>
-
 
 static const upb_msgdef msgs[22];
 static const upb_fielddef fields[105];
@@ -6416,6 +7478,8 @@ typedef struct {
   /* Index of the first def that is under this scope.  For msgdefs, the
    * msgdef itself is at start-1. */
   int start;
+  uint32_t oneof_start;
+  uint32_t oneof_index;
 } upb_descreader_frame;
 
 /* The maximum number of nested declarations that are allowed, ie.
@@ -6436,6 +7500,7 @@ struct upb_descreader {
   upb_filedef *file;  /* The last file in files. */
   upb_descreader_frame stack[UPB_MAX_MESSAGE_NESTING];
   int stack_len;
+  upb_inttable oneofs;
 
   uint32_t number;
   char *name;
@@ -6447,7 +7512,7 @@ struct upb_descreader {
   upb_fielddef *f;
 };
 
-static char *upb_strndup(const char *buf, size_t n) {
+static char *upb_gstrndup(const char *buf, size_t n) {
   char *ret = upb_gmalloc(n + 1);
   if (!ret) return NULL;
   memcpy(ret, buf, n);
@@ -6498,9 +7563,9 @@ static bool upb_descreader_qualify(upb_filedef *f, char *str, int32_t start) {
 
 static upb_msgdef *upb_descreader_top(upb_descreader *r) {
   int index;
-  assert(r->stack_len > 1);
+  UPB_ASSERT(r->stack_len > 1);
   index = r->stack[r->stack_len-1].start - 1;
-  assert(index >= 0);
+  UPB_ASSERT(index >= 0);
   return upb_downcast_msgdef_mutable(upb_filedef_mutabledef(r->file, index));
 }
 
@@ -6513,16 +7578,27 @@ static upb_def *upb_descreader_last(upb_descreader *r) {
 void upb_descreader_startcontainer(upb_descreader *r) {
   upb_descreader_frame *f = &r->stack[r->stack_len++];
   f->start = upb_filedef_defcount(r->file);
+  f->oneof_start = upb_inttable_count(&r->oneofs);
+  f->oneof_index = 0;
   f->name = NULL;
 }
 
 bool upb_descreader_endcontainer(upb_descreader *r) {
-  upb_descreader_frame *f = &r->stack[--r->stack_len];
+  upb_descreader_frame *f = &r->stack[r->stack_len - 1];
+
+  while (upb_inttable_count(&r->oneofs) > f->oneof_start) {
+    upb_oneofdef *o = upb_value_getptr(upb_inttable_pop(&r->oneofs));
+    bool ok = upb_msgdef_addoneof(upb_descreader_top(r), o, &r->oneofs, NULL);
+    UPB_ASSERT(ok);
+  }
+
   if (!upb_descreader_qualify(r->file, f->name, f->start)) {
     return false;
   }
   upb_gfree(f->name);
   f->name = NULL;
+
+  r->stack_len--;
   return true;
 }
 
@@ -6532,6 +7608,26 @@ void upb_descreader_setscopename(upb_descreader *r, char *str) {
   f->name = str;
 }
 
+static upb_oneofdef *upb_descreader_getoneof(upb_descreader *r,
+                                             uint32_t index) {
+  bool found;
+  upb_value val;
+  upb_descreader_frame *f = &r->stack[r->stack_len-1];
+
+  /* DescriptorProto messages can be nested, so we will see the nested messages
+   * between when we see the FieldDescriptorProto and the OneofDescriptorProto.
+   * We need to preserve the oneofs in between these two things. */
+  index += f->oneof_start;
+
+  while (upb_inttable_count(&r->oneofs) <= index) {
+    upb_inttable_push(&r->oneofs, upb_value_ptr(upb_oneofdef_new(&r->oneofs)));
+  }
+
+  found = upb_inttable_lookup(&r->oneofs, index, &val);
+  UPB_ASSERT(found);
+  return upb_value_getptr(val);
+}
+
 /** Handlers for google.protobuf.FileDescriptorSet. ***************************/
 
 static void *fileset_startfile(void *closure, const void *hd) {
@@ -6566,11 +7662,11 @@ static size_t file_onname(void *closure, const void *hd, const char *buf,
   UPB_UNUSED(hd);
   UPB_UNUSED(handle);
 
-  name = upb_strndup(buf, n);
+  name = upb_gstrndup(buf, n);
   /* XXX: see comment at the top of the file. */
   ok = upb_filedef_setname(r->file, name, NULL);
   upb_gfree(name);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return n;
 }
 
@@ -6582,11 +7678,11 @@ static size_t file_onpackage(void *closure, const void *hd, const char *buf,
   UPB_UNUSED(hd);
   UPB_UNUSED(handle);
 
-  package = upb_strndup(buf, n);
+  package = upb_gstrndup(buf, n);
   /* XXX: see comment at the top of the file. */
   upb_descreader_setscopename(r, package);
   ok = upb_filedef_setpackage(r->file, package, NULL);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return n;
 }
 
@@ -6605,7 +7701,7 @@ static size_t file_onsyntax(void *closure, const void *hd, const char *buf,
     ok = false;
   }
 
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return n;
 }
 
@@ -6614,7 +7710,7 @@ static void *file_startmsg(void *closure, const void *hd) {
   upb_msgdef *m = upb_msgdef_new(&m);
   bool ok = upb_filedef_addmsg(r->file, m, &m, NULL);
   UPB_UNUSED(hd);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return r;
 }
 
@@ -6623,7 +7719,7 @@ static void *file_startenum(void *closure, const void *hd) {
   upb_enumdef *e = upb_enumdef_new(&e);
   bool ok = upb_filedef_addenum(r->file, e, &e, NULL);
   UPB_UNUSED(hd);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return r;
 }
 
@@ -6633,7 +7729,7 @@ static void *file_startext(void *closure, const void *hd) {
   r->f = upb_fielddef_new(r);
   ok = upb_filedef_addext(r->file, r->f, r, NULL);
   UPB_UNUSED(hd);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return r;
 }
 
@@ -6654,7 +7750,7 @@ static size_t enumval_onname(void *closure, const void *hd, const char *buf,
   UPB_UNUSED(handle);
   /* XXX: see comment at the top of the file. */
   upb_gfree(r->name);
-  r->name = upb_strndup(buf, n);
+  r->name = upb_gstrndup(buf, n);
   r->saw_name = true;
   return n;
 }
@@ -6705,7 +7801,7 @@ static bool enum_endmsg(void *closure, const void *hd, upb_status *status) {
 static size_t enum_onname(void *closure, const void *hd, const char *buf,
                           size_t n, const upb_bufhandle *handle) {
   upb_descreader *r = closure;
-  char *fullname = upb_strndup(buf, n);
+  char *fullname = upb_gstrndup(buf, n);
   UPB_UNUSED(hd);
   UPB_UNUSED(handle);
   /* XXX: see comment at the top of the file. */
@@ -6719,7 +7815,7 @@ static size_t enum_onname(void *closure, const void *hd, const char *buf,
 static bool field_startmsg(void *closure, const void *hd) {
   upb_descreader *r = closure;
   UPB_UNUSED(hd);
-  assert(r->f);
+  UPB_ASSERT(r->f);
   upb_gfree(r->default_string);
   r->default_string = NULL;
 
@@ -6805,9 +7901,9 @@ static bool field_endmsg(void *closure, const void *hd, upb_status *status) {
   UPB_UNUSED(hd);
 
   /* TODO: verify that all required fields were present. */
-  assert(upb_fielddef_number(f) != 0);
-  assert(upb_fielddef_name(f) != NULL);
-  assert((upb_fielddef_subdefname(f) != NULL) == upb_fielddef_hassubdef(f));
+  UPB_ASSERT(upb_fielddef_number(f) != 0);
+  UPB_ASSERT(upb_fielddef_name(f) != NULL);
+  UPB_ASSERT((upb_fielddef_subdefname(f) != NULL) == upb_fielddef_hassubdef(f));
 
   if (r->default_string) {
     if (upb_fielddef_issubmsg(f)) {
@@ -6866,14 +7962,14 @@ static bool field_onnumber(void *closure, const void *hd, int32_t val) {
   UPB_UNUSED(hd);
 
   ok = upb_fielddef_setnumber(r->f, val, NULL);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return true;
 }
 
 static size_t field_onname(void *closure, const void *hd, const char *buf,
                            size_t n, const upb_bufhandle *handle) {
   upb_descreader *r = closure;
-  char *name = upb_strndup(buf, n);
+  char *name = upb_gstrndup(buf, n);
   UPB_UNUSED(hd);
   UPB_UNUSED(handle);
 
@@ -6886,7 +7982,7 @@ static size_t field_onname(void *closure, const void *hd, const char *buf,
 static size_t field_ontypename(void *closure, const void *hd, const char *buf,
                                size_t n, const upb_bufhandle *handle) {
   upb_descreader *r = closure;
-  char *name = upb_strndup(buf, n);
+  char *name = upb_gstrndup(buf, n);
   UPB_UNUSED(hd);
   UPB_UNUSED(handle);
 
@@ -6899,7 +7995,7 @@ static size_t field_ontypename(void *closure, const void *hd, const char *buf,
 static size_t field_onextendee(void *closure, const void *hd, const char *buf,
                                size_t n, const upb_bufhandle *handle) {
   upb_descreader *r = closure;
-  char *name = upb_strndup(buf, n);
+  char *name = upb_gstrndup(buf, n);
   UPB_UNUSED(hd);
   UPB_UNUSED(handle);
 
@@ -6919,7 +8015,34 @@ static size_t field_ondefaultval(void *closure, const void *hd, const char *buf,
    * type yet, so we save it as a string until the end of the field.
    * XXX: see comment at the top of the file. */
   upb_gfree(r->default_string);
-  r->default_string = upb_strndup(buf, n);
+  r->default_string = upb_gstrndup(buf, n);
+  return n;
+}
+
+static bool field_ononeofindex(void *closure, const void *hd, int32_t index) {
+  upb_descreader *r = closure;
+  upb_oneofdef *o = upb_descreader_getoneof(r, index);
+  bool ok = upb_oneofdef_addfield(o, r->f, &r->f, NULL);
+  UPB_UNUSED(hd);
+
+  UPB_ASSERT(ok);
+  return true;
+}
+
+/** Handlers for google.protobuf.OneofDescriptorProto. ************************/
+
+static size_t oneof_name(void *closure, const void *hd, const char *buf,
+                         size_t n, const upb_bufhandle *handle) {
+  upb_descreader *r = closure;
+  upb_descreader_frame *f = &r->stack[r->stack_len-1];
+  upb_oneofdef *o = upb_descreader_getoneof(r, f->oneof_index++);
+  char *name_null_terminated = upb_gstrndup(buf, n);
+  bool ok = upb_oneofdef_setname(o, name_null_terminated, NULL);
+  UPB_UNUSED(hd);
+  UPB_UNUSED(handle);
+
+  UPB_ASSERT(ok);
+  free(name_null_terminated);
   return n;
 }
 
@@ -6950,7 +8073,7 @@ static size_t msg_name(void *closure, const void *hd, const char *buf,
   upb_descreader *r = closure;
   upb_msgdef *m = upb_descreader_top(r);
   /* XXX: see comment at the top of the file. */
-  char *name = upb_strndup(buf, n);
+  char *name = upb_gstrndup(buf, n);
   UPB_UNUSED(hd);
   UPB_UNUSED(handle);
 
@@ -6964,7 +8087,7 @@ static void *msg_startmsg(void *closure, const void *hd) {
   upb_msgdef *m = upb_msgdef_new(&m);
   bool ok = upb_filedef_addmsg(r->file, m, &m, NULL);
   UPB_UNUSED(hd);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return r;
 }
 
@@ -6973,7 +8096,7 @@ static void *msg_startext(void *closure, const void *hd) {
   upb_fielddef *f = upb_fielddef_new(&f);
   bool ok = upb_filedef_addext(r->file, f, &f, NULL);
   UPB_UNUSED(hd);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return r;
 }
 
@@ -6989,9 +8112,15 @@ static void *msg_startfield(void *closure, const void *hd) {
 static bool msg_endfield(void *closure, const void *hd) {
   upb_descreader *r = closure;
   upb_msgdef *m = upb_descreader_top(r);
+  bool ok;
   UPB_UNUSED(hd);
 
-  upb_msgdef_addfield(m, r->f, &r->f, NULL);
+  /* Oneof fields are added to the msgdef through their oneof, so don't need to
+   * be added here. */
+  if (upb_fielddef_containingoneof(r->f) == NULL) {
+    ok = upb_msgdef_addfield(m, r->f, &r->f, NULL);
+    UPB_ASSERT(ok);
+  }
   r->f = NULL;
   return true;
 }
@@ -7074,6 +8203,10 @@ static void reghandlers(const void *closure, upb_handlers *h) {
                            &field_onextendee, NULL);
     upb_handlers_setstring(h, F(FieldDescriptorProto, default_value),
                            &field_ondefaultval, NULL);
+    upb_handlers_setint32(h, F(FieldDescriptorProto, oneof_index),
+                          &field_ononeofindex, NULL);
+  } else if (upbdefs_google_protobuf_OneofDescriptorProto_is(m)) {
+    upb_handlers_setstring(h, F(OneofDescriptorProto, name), &oneof_name, NULL);
   } else if (upbdefs_google_protobuf_FieldOptions_is(m)) {
     upb_handlers_setbool(h, F(FieldOptions, lazy), &field_onlazy, NULL);
     upb_handlers_setbool(h, F(FieldOptions, packed), &field_onpacked, NULL);
@@ -7081,7 +8214,7 @@ static void reghandlers(const void *closure, upb_handlers *h) {
     upb_handlers_setbool(h, F(MessageOptions, map_entry), &msg_onmapentry, NULL);
   }
 
-  assert(upb_ok(upb_handlers_status(h)));
+  UPB_ASSERT(upb_ok(upb_handlers_status(h)));
 }
 
 #undef F
@@ -7096,6 +8229,7 @@ void descreader_cleanup(void *_r) {
 
   upb_gfree(r->name);
   upb_inttable_uninit(&r->files);
+  upb_inttable_uninit(&r->oneofs);
   upb_gfree(r->default_string);
   while (r->stack_len > 0) {
     upb_descreader_frame *f = &r->stack[--r->stack_len];
@@ -7113,6 +8247,7 @@ upb_descreader *upb_descreader_create(upb_env *e, const upb_handlers *h) {
   }
 
   upb_inttable_init(&r->files, UPB_CTYPE_PTR);
+  upb_inttable_init(&r->oneofs, UPB_CTYPE_PTR);
   upb_sink_reset(upb_descreader_input(r), h, r);
   r->stack_len = 0;
   r->name = NULL;
@@ -7327,7 +8462,7 @@ bool op_has_longofs(int32_t instruction) {
     case OP_TAGN:
       return false;
     default:
-      assert(false);
+      UPB_ASSERT(false);
       return false;
   }
 }
@@ -7346,7 +8481,7 @@ static void setofs(uint32_t *instruction, int32_t ofs) {
   } else {
     *instruction = (*instruction & ~0xff00) | ((ofs & 0xff) << 8);
   }
-  assert(getofs(*instruction) == ofs);  /* Would fail in cases of overflow. */
+  UPB_ASSERT(getofs(*instruction) == ofs);  /* Would fail in cases of overflow. */
 }
 
 static uint32_t pcofs(compiler *c) { return c->pc - c->group->bytecode; }
@@ -7358,7 +8493,7 @@ static void label(compiler *c, unsigned int label) {
   int val;
   uint32_t *codep;
 
-  assert(label < MAXLABEL);
+  UPB_ASSERT(label < MAXLABEL);
   val = c->fwd_labels[label];
   codep = (val == EMPTYLABEL) ? NULL : c->group->bytecode + val;
   while (codep) {
@@ -7379,7 +8514,7 @@ static void label(compiler *c, unsigned int label) {
  * The returned value is the offset that should be written into the instruction.
  */
 static int32_t labelref(compiler *c, int label) {
-  assert(label < MAXLABEL);
+  UPB_ASSERT(label < MAXLABEL);
   if (label == LABEL_DISPATCH) {
     /* No resolving required. */
     return 0;
@@ -7479,7 +8614,7 @@ static void putop(compiler *c, opcode op, ...) {
       int label = va_arg(ap, int);
       uint64_t tag = va_arg(ap, uint64_t);
       uint32_t instruction = op | (tag << 16);
-      assert(tag <= 0xffff);
+      UPB_ASSERT(tag <= 0xffff);
       setofs(&instruction, labelref(c, label));
       put32(c, instruction);
       break;
@@ -7616,7 +8751,7 @@ static uint64_t get_encoded_tag(const upb_fielddef *f, int wire_type) {
   uint32_t tag = (upb_fielddef_number(f) << 3) | wire_type;
   uint64_t encoded_tag = upb_vencode32(tag);
   /* No tag should be greater than 5 bytes. */
-  assert(encoded_tag <= 0xffffffffff);
+  UPB_ASSERT(encoded_tag <= 0xffffffffff);
   return encoded_tag;
 }
 
@@ -7639,7 +8774,7 @@ static void putchecktag(compiler *c, const upb_fielddef *f,
 static upb_selector_t getsel(const upb_fielddef *f, upb_handlertype_t type) {
   upb_selector_t selector;
   bool ok = upb_handlers_getselector(f, type, &selector);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return selector;
 }
 
@@ -7651,7 +8786,7 @@ static uint64_t repack(uint64_t dispatch, int new_wt2) {
   uint8_t wt1;
   uint8_t old_wt2;
   upb_pbdecoder_unpackdispatch(dispatch, &ofs, &wt1, &old_wt2);
-  assert(old_wt2 == NO_WIRE_TYPE);  /* wt2 should not be set yet. */
+  UPB_ASSERT(old_wt2 == NO_WIRE_TYPE);  /* wt2 should not be set yet. */
   return upb_pbdecoder_packdispatch(ofs, wt1, new_wt2);
 }
 
@@ -7853,7 +8988,7 @@ static void generate_primitivefield(compiler *c, const upb_fielddef *f,
    * setting in the fielddef.  This will favor (in speed) whichever was
    * specified. */
 
-  assert((int)parse_type >= 0 && parse_type <= OP_MAX);
+  UPB_ASSERT((int)parse_type >= 0 && parse_type <= OP_MAX);
   sel = getsel(f, upb_handlers_getprimitivehandlertype(f));
   wire_type = upb_pb_native_wire_types[upb_fielddef_descriptortype(f)];
   if (upb_fielddef_isseq(f)) {
@@ -7895,7 +9030,7 @@ static void compile_method(compiler *c, upb_pbdecodermethod *method) {
   upb_msg_field_iter i;
   upb_value val;
 
-  assert(method);
+  UPB_ASSERT(method);
 
   /* Clear all entries in the dispatch table. */
   upb_inttable_uninit(&method->dispatch);
@@ -8043,7 +9178,7 @@ const mgroup *mgroup_new(const upb_handlers *dest, bool allowjit, bool lazy,
   compiler *c;
 
   UPB_UNUSED(allowjit);
-  assert(upb_handlers_isfrozen(dest));
+  UPB_ASSERT(upb_handlers_isfrozen(dest));
 
   g = newgroup(owner);
   c = newcompiler(g, lazy);
@@ -8064,13 +9199,13 @@ const mgroup *mgroup_new(const upb_handlers *dest, bool allowjit, bool lazy,
 #ifdef UPB_DUMP_BYTECODE
   {
     FILE *f = fopen("/tmp/upb-bytecode", "w");
-    assert(f);
+    UPB_ASSERT(f);
     dumpbc(g->bytecode, g->bytecode_end, stderr);
     dumpbc(g->bytecode, g->bytecode_end, f);
     fclose(f);
 
     f = fopen("/tmp/upb-bytecode.bin", "wb");
-    assert(f);
+    UPB_ASSERT(f);
     fwrite(g->bytecode, 1, g->bytecode_end - g->bytecode, f);
     fclose(f);
   }
@@ -8120,7 +9255,7 @@ const upb_pbdecodermethod *upb_pbcodecache_getdecodermethod(
   upb_inttable_push(&c->groups, upb_value_constptr(g));
 
   ok = upb_inttable_lookupptr(&g->methods, opts->handlers, &v);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return upb_value_getptr(v);
 }
 
@@ -8253,7 +9388,7 @@ void upb_pbdecoder_seterr(upb_pbdecoder *d, const char *msg) {
 /* How many bytes can be safely read from d->ptr without reading past end-of-buf
  * or past the current delimited end. */
 static size_t curbufleft(const upb_pbdecoder *d) {
-  assert(d->data_end >= d->ptr);
+  UPB_ASSERT(d->data_end >= d->ptr);
   return d->data_end - d->ptr;
 }
 
@@ -8274,7 +9409,7 @@ size_t delim_remaining(const upb_pbdecoder *d) {
 
 /* Advances d->ptr. */
 static void advance(upb_pbdecoder *d, size_t len) {
-  assert(curbufleft(d) >= len);
+  UPB_ASSERT(curbufleft(d) >= len);
   d->ptr += len;
 }
 
@@ -8307,7 +9442,7 @@ static void switchtobuf(upb_pbdecoder *d, const char *buf, const char *end) {
 }
 
 static void advancetobuf(upb_pbdecoder *d, const char *buf, size_t len) {
-  assert(curbufleft(d) == 0);
+  UPB_ASSERT(curbufleft(d) == 0);
   d->bufstart_ofs += (d->end - d->buf);
   switchtobuf(d, buf, buf + len);
 }
@@ -8316,7 +9451,7 @@ static void checkpoint(upb_pbdecoder *d) {
   /* The assertion here is in the interests of efficiency, not correctness.
    * We are trying to ensure that we don't checkpoint() more often than
    * necessary. */
-  assert(d->checkpoint != d->ptr);
+  UPB_ASSERT(d->checkpoint != d->ptr);
   d->checkpoint = d->ptr;
 }
 
@@ -8327,8 +9462,8 @@ static void checkpoint(upb_pbdecoder *d) {
  * won't actually be read.
  */
 static int32_t skip(upb_pbdecoder *d, size_t bytes) {
-  assert(!in_residual_buf(d, d->ptr) || d->size_param == 0);
-  assert(d->skip == 0);
+  UPB_ASSERT(!in_residual_buf(d, d->ptr) || d->size_param == 0);
+  UPB_ASSERT(d->skip == 0);
   if (bytes > delim_remaining(d)) {
     seterr(d, "Skipped value extended beyond enclosing submessage.");
     return upb_pbdecoder_suspend(d);
@@ -8356,7 +9491,7 @@ int32_t upb_pbdecoder_resume(upb_pbdecoder *d, void *p, const char *buf,
 
   /* d->skip and d->residual_end could probably elegantly be represented
    * as a single variable, to more easily represent this invariant. */
-  assert(!(d->skip && d->residual_end > d->residual));
+  UPB_ASSERT(!(d->skip && d->residual_end > d->residual));
 
   /* We need to remember the original size_param, so that the value we return
    * is relative to it, even if we do some skipping first. */
@@ -8389,7 +9524,7 @@ int32_t upb_pbdecoder_resume(upb_pbdecoder *d, void *p, const char *buf,
 
   if (d->residual_end > d->residual) {
     /* We have residual bytes from the last buffer. */
-    assert(d->ptr == d->residual);
+    UPB_ASSERT(d->ptr == d->residual);
   } else {
     switchtobuf(d, buf, buf + size);
   }
@@ -8423,8 +9558,8 @@ size_t upb_pbdecoder_suspend(upb_pbdecoder *d) {
     return 0;
   } else {
     size_t ret = d->size_param - (d->end - d->checkpoint);
-    assert(!in_residual_buf(d, d->checkpoint));
-    assert(d->buf == d->buf_param || d->buf == &dummy_char);
+    UPB_ASSERT(!in_residual_buf(d, d->checkpoint));
+    UPB_ASSERT(d->buf == d->buf_param || d->buf == &dummy_char);
 
     d->bufstart_ofs += (d->checkpoint - d->buf);
     d->residual_end = d->residual;
@@ -8444,7 +9579,7 @@ static size_t suspend_save(upb_pbdecoder *d) {
 
   if (d->checkpoint == d->residual) {
     /* Checkpoint was in residual buf; append user byte(s) to residual buf. */
-    assert((d->residual_end - d->residual) + d->size_param <=
+    UPB_ASSERT((d->residual_end - d->residual) + d->size_param <=
            sizeof(d->residual));
     if (!in_residual_buf(d, d->ptr)) {
       d->bufstart_ofs -= (d->residual_end - d->residual);
@@ -8454,11 +9589,11 @@ static size_t suspend_save(upb_pbdecoder *d) {
   } else {
     /* Checkpoint was in user buf; old residual bytes not needed. */
     size_t save;
-    assert(!in_residual_buf(d, d->checkpoint));
+    UPB_ASSERT(!in_residual_buf(d, d->checkpoint));
 
     d->ptr = d->checkpoint;
     save = curbufleft(d);
-    assert(save <= sizeof(d->residual));
+    UPB_ASSERT(save <= sizeof(d->residual));
     memcpy(d->residual, d->ptr, save);
     d->residual_end = d->residual + save;
     d->bufstart_ofs = offset(d);
@@ -8472,7 +9607,7 @@ static size_t suspend_save(upb_pbdecoder *d) {
  * Requires that this many bytes are available in the current buffer. */
 UPB_FORCEINLINE static void consumebytes(upb_pbdecoder *d, void *buf,
                                          size_t bytes) {
-  assert(bytes <= curbufleft(d));
+  UPB_ASSERT(bytes <= curbufleft(d));
   memcpy(buf, d->ptr, bytes);
   advance(d, bytes);
 }
@@ -8485,7 +9620,7 @@ UPB_NOINLINE static int32_t getbytes_slow(upb_pbdecoder *d, void *buf,
   const size_t avail = curbufleft(d);
   consumebytes(d, buf, avail);
   bytes -= avail;
-  assert(bytes > 0);
+  UPB_ASSERT(bytes > 0);
   if (in_residual_buf(d, d->ptr)) {
     advancetobuf(d, d->buf_param, d->size_param);
   }
@@ -8668,7 +9803,7 @@ UPB_NOINLINE int32_t upb_pbdecoder_checktag_slow(upb_pbdecoder *d,
   if (read == bytes && data == expected) {
     /* Advance past matched bytes. */
     int32_t ok = getbytes(d, &data, read);
-    UPB_ASSERT_VAR(ok, ok < 0);
+    UPB_ASSERT(ok < 0);
     return DECODE_OK;
   } else if (read < bytes && memcmp(&data, &expected, read) == 0) {
     return suspend_save(d);
@@ -8743,7 +9878,7 @@ have_tag:
 static void goto_endmsg(upb_pbdecoder *d) {
   upb_value v;
   bool found = upb_inttable_lookup32(d->top->dispatch, DISPATCH_ENDMSG, &v);
-  UPB_ASSERT_VAR(found, found);
+  UPB_ASSERT(found);
   d->pc = d->top->base + upb_value_getuint64(v);
 }
 
@@ -8777,7 +9912,7 @@ static int32_t dispatch(upb_pbdecoder *d) {
     } else if (wire_type == ((v >> 8) & 0xff)) {
       bool found =
           upb_inttable_lookup(dispatch, fieldnum + UPB_MAX_FIELDNUMBER, &val);
-      UPB_ASSERT_VAR(found, found);
+      UPB_ASSERT(found);
       d->pc = d->top->base + upb_value_getuint64(val);
       return DECODE_OK;
     }
@@ -8789,7 +9924,7 @@ static int32_t dispatch(upb_pbdecoder *d) {
    * can re-check the delimited end. */
   d->last--;  /* Necessary if we get suspended */
   d->pc = d->last;
-  assert(getop(*d->last) == OP_CHECKDELIM);
+  UPB_ASSERT(getop(*d->last) == OP_CHECKDELIM);
 
   /* Unknown field or ENDGROUP. */
   retval = upb_pbdecoder_skipunknown(d, fieldnum, wire_type);
@@ -8807,7 +9942,7 @@ static int32_t dispatch(upb_pbdecoder *d) {
 /* Callers know that the stack is more than one deep because the opcodes that
  * call this only occur after PUSH operations. */
 upb_pbdecoder_frame *outer_frame(upb_pbdecoder *d) {
-  assert(d->top != d->stack);
+  UPB_ASSERT(d->top != d->stack);
   return d->top - 1;
 }
 
@@ -8839,7 +9974,7 @@ size_t run_decoder_vm(upb_pbdecoder *d, const mgroup *group,
     op = getop(instruction);
     arg = instruction >> 8;
     longofs = arg;
-    assert(d->ptr != d->residual_end);
+    UPB_ASSERT(d->ptr != d->residual_end);
     UPB_UNUSED(group);
 #ifdef UPB_DUMP_BYTECODE
     fprintf(stderr, "s_ofs=%d buf_ofs=%d data_rem=%d buf_rem=%d delim_rem=%d "
@@ -8914,7 +10049,7 @@ size_t run_decoder_vm(upb_pbdecoder *d, const mgroup *group,
           } else {
             int32_t ret = skip(d, n);
             /* This shouldn't return DECODE_OK, because n > len. */
-            assert(ret >= 0);
+            UPB_ASSERT(ret >= 0);
             return ret;
           }
         }
@@ -8936,7 +10071,7 @@ size_t run_decoder_vm(upb_pbdecoder *d, const mgroup *group,
         d->top->groupnum = *d->pc++;
       )
       VMCASE(OP_POP,
-        assert(d->top > d->stack);
+        UPB_ASSERT(d->top > d->stack);
         decoder_pop(d);
       )
       VMCASE(OP_PUSHLENDELIM,
@@ -8952,7 +10087,7 @@ size_t run_decoder_vm(upb_pbdecoder *d, const mgroup *group,
         /* We are guaranteed of this assert because we never allow ourselves to
          * consume bytes beyond data_end, which covers delim_end when non-NULL.
          */
-        assert(!(d->delim_end && d->ptr > d->delim_end));
+        UPB_ASSERT(!(d->delim_end && d->ptr > d->delim_end));
         if (d->ptr == d->delim_end)
           d->pc += longofs;
       )
@@ -8961,7 +10096,7 @@ size_t run_decoder_vm(upb_pbdecoder *d, const mgroup *group,
         d->pc += longofs;
       )
       VMCASE(OP_RET,
-        assert(d->call_len > 0);
+        UPB_ASSERT(d->call_len > 0);
         d->pc = d->callstack[--d->call_len];
       )
       VMCASE(OP_BRANCH,
@@ -9088,7 +10223,7 @@ bool upb_pbdecoder_end(void *closure, const void *handler_data) {
     if (p != method->code_base.ptr) p--;
     if (getop(*p) == OP_CHECKDELIM) {
       /* Rewind from OP_TAG* to OP_CHECKDELIM. */
-      assert(getop(*d->pc) == OP_TAG1 ||
+      UPB_ASSERT(getop(*d->pc) == OP_TAG1 ||
              getop(*d->pc) == OP_TAG2 ||
              getop(*d->pc) == OP_TAGN ||
              getop(*d->pc) == OP_DISPATCH);
@@ -9152,7 +10287,7 @@ upb_pbdecoder *upb_pbdecoder_create(upb_env *e, const upb_pbdecodermethod *m,
   upb_pbdecoder_reset(d);
   upb_bytessink_reset(&d->input_, &m->input_handler_, d);
 
-  assert(sink);
+  UPB_ASSERT(sink);
   if (d->method_->dest_handlers_) {
     if (sink->handlers != d->method_->dest_handlers_)
       return NULL;
@@ -9160,7 +10295,8 @@ upb_pbdecoder *upb_pbdecoder_create(upb_env *e, const upb_pbdecodermethod *m,
   upb_sink_reset(&d->top->sink, sink->handlers, sink->closure);
 
   /* If this fails, increase the value in decoder.h. */
-  assert(upb_env_bytesallocated(e) - size_before <= UPB_PB_DECODER_SIZE);
+  UPB_ASSERT_DEBUGVAR(upb_env_bytesallocated(e) - size_before <=
+                      UPB_PB_DECODER_SIZE);
   return d;
 }
 
@@ -9181,7 +10317,7 @@ size_t upb_pbdecoder_maxnesting(const upb_pbdecoder *d) {
 }
 
 bool upb_pbdecoder_setmaxnesting(upb_pbdecoder *d, size_t max) {
-  assert(d->top >= d->stack);
+  UPB_ASSERT(d->top >= d->stack);
 
   if (max < (size_t)(d->top - d->stack)) {
     /* Can't set a limit smaller than what we are currently at. */
@@ -9340,7 +10476,7 @@ struct upb_pb_encoder {
 /* TODO(haberman): handle pushback */
 static void putbuf(upb_pb_encoder *e, const char *buf, size_t len) {
   size_t n = upb_bytessink_putbuf(e->output_, e->subc, buf, len, NULL);
-  UPB_ASSERT_VAR(n, n == len);
+  UPB_ASSERT(n == len);
 }
 
 static upb_pb_encoder_segment *top(upb_pb_encoder *e) {
@@ -9380,7 +10516,7 @@ static bool reserve(upb_pb_encoder *e, size_t bytes) {
 /* Call when "bytes" bytes have been writte at e->ptr.  The caller *must* have
  * previously called reserve() with at least this many bytes. */
 static void encoder_advance(upb_pb_encoder *e, size_t bytes) {
-  assert((size_t)(e->limit - e->ptr) >= bytes);
+  UPB_ASSERT((size_t)(e->limit - e->ptr) >= bytes);
   e->ptr += bytes;
 }
 
@@ -9415,7 +10551,7 @@ static bool encode_bytes(upb_pb_encoder *e, const void *data, size_t len) {
  * length. */
 static void accumulate(upb_pb_encoder *e) {
   size_t run_len;
-  assert(e->ptr >= e->runbegin);
+  UPB_ASSERT(e->ptr >= e->runbegin);
   run_len = e->ptr - e->runbegin;
   e->segptr->seglen += run_len;
   top(e)->msglen += run_len;
@@ -9770,7 +10906,8 @@ upb_pb_encoder *upb_pb_encoder_create(upb_env *env, const upb_handlers *h,
   e->ptr = e->buf;
 
   /* If this fails, increase the value in encoder.h. */
-  assert(upb_env_bytesallocated(env) - size_before <= UPB_PB_ENCODER_SIZE);
+  UPB_ASSERT_DEBUGVAR(upb_env_bytesallocated(env) - size_before <=
+                      UPB_PB_ENCODER_SIZE);
   return e;
 }
 
@@ -9938,7 +11075,7 @@ bool putf(upb_textprinter *p, const char *fmt, ...) {
   if (!str) return false;
   written = vsprintf(str, fmt, args);
   va_end(args);
-  UPB_ASSERT_VAR(written, written == len);
+  UPB_ASSERT(written == len);
 
   ok = upb_bytessink_putbuf(p->output_, p->subc, str, len, NULL);
   upb_gfree(str);
@@ -10407,7 +11544,7 @@ static upb_selector_t getsel_for_handlertype(upb_json_parser *p,
                                              upb_handlertype_t type) {
   upb_selector_t sel;
   bool ok = upb_handlers_getselector(p->top->f, type, &sel);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   return sel;
 }
 
@@ -10429,7 +11566,7 @@ static bool check_stack(upb_json_parser *p) {
 static void set_name_table(upb_json_parser *p, upb_jsonparser_frame *frame) {
   upb_value v;
   bool ok = upb_inttable_lookupptr(&p->method->name_tables, frame->m, &v);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
   frame->name_table = upb_value_getptr(v);
 }
 
@@ -10552,7 +11689,7 @@ otherchar:
     val = b64lookup(ptr[0]) << 18 |
           b64lookup(ptr[1]) << 12;
 
-    assert(!(val & 0x80000000));
+    UPB_ASSERT(!(val & 0x80000000));
     output = val >> 16;
     upb_sink_putstring(&p->top->sink, sel, &output, 1, NULL);
     return true;
@@ -10606,9 +11743,8 @@ badpadding:
  *      the true value in a contiguous buffer. */
 
 static void assert_accumulate_empty(upb_json_parser *p) {
-  UPB_UNUSED(p);
-  assert(p->accumulated == NULL);
-  assert(p->accumulated_len == 0);
+  UPB_ASSERT(p->accumulated == NULL);
+  UPB_ASSERT(p->accumulated_len == 0);
 }
 
 static void accumulate_clear(upb_json_parser *p) {
@@ -10674,7 +11810,7 @@ static bool accumulate_append(upb_json_parser *p, const char *buf, size_t len,
  * call, and writes the length to *len.  This with point either to the input
  * buffer or a temporary accumulate buffer. */
 static const char *accumulate_getptr(upb_json_parser *p, size_t *len) {
-  assert(p->accumulated);
+  UPB_ASSERT(p->accumulated);
   *len = p->accumulated_len;
   return p->accumulated;
 }
@@ -10712,7 +11848,7 @@ enum {
  * the end. */
 static void multipart_startaccum(upb_json_parser *p) {
   assert_accumulate_empty(p);
-  assert(p->multipart_state == MULTIPART_INACTIVE);
+  UPB_ASSERT(p->multipart_state == MULTIPART_INACTIVE);
   p->multipart_state = MULTIPART_ACCUMULATE;
 }
 
@@ -10720,7 +11856,7 @@ static void multipart_startaccum(upb_json_parser *p) {
  * value with the given selector. */
 static void multipart_start(upb_json_parser *p, upb_selector_t sel) {
   assert_accumulate_empty(p);
-  assert(p->multipart_state == MULTIPART_INACTIVE);
+  UPB_ASSERT(p->multipart_state == MULTIPART_INACTIVE);
   p->multipart_state = MULTIPART_PUSHEAGERLY;
   p->string_selector = sel;
 }
@@ -10753,7 +11889,7 @@ static bool multipart_text(upb_json_parser *p, const char *buf, size_t len,
 /* Note: this invalidates the accumulate buffer!  Call only after reading its
  * contents. */
 static void multipart_end(upb_json_parser *p) {
-  assert(p->multipart_state != MULTIPART_INACTIVE);
+  UPB_ASSERT(p->multipart_state != MULTIPART_INACTIVE);
   p->multipart_state = MULTIPART_INACTIVE;
   accumulate_clear(p);
 }
@@ -10766,13 +11902,13 @@ static void multipart_end(upb_json_parser *p) {
  * region. */
 
 static void capture_begin(upb_json_parser *p, const char *ptr) {
-  assert(p->multipart_state != MULTIPART_INACTIVE);
-  assert(p->capture == NULL);
+  UPB_ASSERT(p->multipart_state != MULTIPART_INACTIVE);
+  UPB_ASSERT(p->capture == NULL);
   p->capture = ptr;
 }
 
 static bool capture_end(upb_json_parser *p, const char *ptr) {
-  assert(p->capture);
+  UPB_ASSERT(p->capture);
   if (multipart_text(p, p->capture, ptr - p->capture, true)) {
     p->capture = NULL;
     return true;
@@ -10805,7 +11941,7 @@ static void capture_suspend(upb_json_parser *p, const char **ptr) {
 
 static void capture_resume(upb_json_parser *p, const char *ptr) {
   if (p->capture) {
-    assert(p->capture == &suspend_capture);
+    UPB_ASSERT(p->capture == &suspend_capture);
     p->capture = ptr;
   }
 }
@@ -10827,7 +11963,7 @@ static char escape_char(char in) {
     case '"': return '"';
     case '\\': return '\\';
     default:
-      assert(0);
+      UPB_ASSERT(0);
       return 'x';
   }
 }
@@ -10851,7 +11987,7 @@ static void hexdigit(upb_json_parser *p, const char *ptr) {
   } else if (ch >= 'a' && ch <= 'f') {
     p->digit += ((ch - 'a') + 10);
   } else {
-    assert(ch >= 'A' && ch <= 'F');
+    UPB_ASSERT(ch >= 'A' && ch <= 'F');
     p->digit += ((ch - 'A') + 10);
   }
 }
@@ -10982,7 +12118,7 @@ static bool parse_number(upb_json_parser *p) {
       break;
     }
     default:
-      assert(false);
+      UPB_ASSERT(false);
   }
 
   multipart_end(p);
@@ -11008,13 +12144,13 @@ static bool parser_putbool(upb_json_parser *p, bool val) {
   }
 
   ok = upb_sink_putbool(&p->top->sink, parser_getsel(p), val);
-  UPB_ASSERT_VAR(ok, ok);
+  UPB_ASSERT(ok);
 
   return true;
 }
 
 static bool start_stringval(upb_json_parser *p) {
-  assert(p->top->f);
+  UPB_ASSERT(p->top->f);
 
   if (upb_fielddef_isstring(p->top->f)) {
     upb_jsonparser_frame *inner;
@@ -11104,7 +12240,7 @@ static bool end_stringval(upb_json_parser *p) {
     }
 
     default:
-      assert(false);
+      UPB_ASSERT(false);
       upb_status_seterrmsg(&p->status, "Internal error in JSON decoder");
       upb_env_reporterror(p->env, &p->status);
       ok = false;
@@ -11117,7 +12253,7 @@ static bool end_stringval(upb_json_parser *p) {
 }
 
 static void start_member(upb_json_parser *p) {
-  assert(!p->top->f);
+  UPB_ASSERT(!p->top->f);
   multipart_startaccum(p);
 }
 
@@ -11246,7 +12382,7 @@ static bool handle_mapentry(upb_json_parser *p) {
 }
 
 static bool end_membername(upb_json_parser *p) {
-  assert(!p->top->f);
+  UPB_ASSERT(!p->top->f);
 
   if (p->top->is_map) {
     return handle_mapentry(p);
@@ -11278,7 +12414,7 @@ static void end_member(upb_json_parser *p) {
     bool ok;
     const upb_fielddef *mapfield;
 
-    assert(p->top > p->stack);
+    UPB_ASSERT(p->top > p->stack);
     /* send ENDMSG on submsg. */
     upb_sink_endmsg(&p->top->sink, &s);
     mapfield = p->top->mapfield;
@@ -11286,7 +12422,7 @@ static void end_member(upb_json_parser *p) {
     /* send ENDSUBMSG in repeated-field-of-mapentries frame. */
     p->top--;
     ok = upb_handlers_getselector(mapfield, UPB_HANDLER_ENDSUBMSG, &sel);
-    UPB_ASSERT_VAR(ok, ok);
+    UPB_ASSERT(ok);
     upb_sink_endsubmsg(&p->top->sink, sel);
   }
 
@@ -11294,7 +12430,7 @@ static void end_member(upb_json_parser *p) {
 }
 
 static bool start_subobject(upb_json_parser *p) {
-  assert(p->top->f);
+  UPB_ASSERT(p->top->f);
 
   if (upb_fielddef_ismap(p->top->f)) {
     upb_jsonparser_frame *inner;
@@ -11363,7 +12499,7 @@ static bool start_array(upb_json_parser *p) {
   upb_jsonparser_frame *inner;
   upb_selector_t sel;
 
-  assert(p->top->f);
+  UPB_ASSERT(p->top->f);
 
   if (!upb_fielddef_isseq(p->top->f)) {
     upb_status_seterrf(&p->status,
@@ -11391,7 +12527,7 @@ static bool start_array(upb_json_parser *p) {
 static void end_array(upb_json_parser *p) {
   upb_selector_t sel;
 
-  assert(p->top > p->stack);
+  UPB_ASSERT(p->top > p->stack);
 
   p->top--;
   sel = getsel_for_handlertype(p, UPB_HANDLER_ENDSEQ);
@@ -11437,11 +12573,11 @@ static void end_object(upb_json_parser *p) {
  * final state once, when the closing '"' is seen. */
 
 
-#line 1245 "upb/json/parser.rl"
+#line 1244 "upb/json/parser.rl"
 
 
 
-#line 1157 "upb/json/parser.c"
+#line 1156 "upb/json/parser.c"
 static const char _json_actions[] = {
 	0, 1, 0, 1, 2, 1, 3, 1, 
 	5, 1, 6, 1, 7, 1, 8, 1, 
@@ -11590,7 +12726,7 @@ static const int json_en_value_machine = 27;
 static const int json_en_main = 1;
 
 
-#line 1248 "upb/json/parser.rl"
+#line 1247 "upb/json/parser.rl"
 
 size_t parse(void *closure, const void *hd, const char *buf, size_t size,
              const upb_bufhandle *handle) {
@@ -11612,7 +12748,7 @@ size_t parse(void *closure, const void *hd, const char *buf, size_t size,
   capture_resume(parser, buf);
 
   
-#line 1328 "upb/json/parser.c"
+#line 1327 "upb/json/parser.c"
 	{
 	int _klen;
 	unsigned int _trans;
@@ -11687,118 +12823,118 @@ _match:
 		switch ( *_acts++ )
 		{
 	case 0:
-#line 1160 "upb/json/parser.rl"
+#line 1159 "upb/json/parser.rl"
 	{ p--; {cs = stack[--top]; goto _again;} }
 	break;
 	case 1:
-#line 1161 "upb/json/parser.rl"
+#line 1160 "upb/json/parser.rl"
 	{ p--; {stack[top++] = cs; cs = 10; goto _again;} }
 	break;
 	case 2:
-#line 1165 "upb/json/parser.rl"
+#line 1164 "upb/json/parser.rl"
 	{ start_text(parser, p); }
 	break;
 	case 3:
-#line 1166 "upb/json/parser.rl"
+#line 1165 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(end_text(parser, p)); }
 	break;
 	case 4:
-#line 1172 "upb/json/parser.rl"
+#line 1171 "upb/json/parser.rl"
 	{ start_hex(parser); }
 	break;
 	case 5:
-#line 1173 "upb/json/parser.rl"
+#line 1172 "upb/json/parser.rl"
 	{ hexdigit(parser, p); }
 	break;
 	case 6:
-#line 1174 "upb/json/parser.rl"
+#line 1173 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(end_hex(parser)); }
 	break;
 	case 7:
-#line 1180 "upb/json/parser.rl"
+#line 1179 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(escape(parser, p)); }
 	break;
 	case 8:
-#line 1186 "upb/json/parser.rl"
+#line 1185 "upb/json/parser.rl"
 	{ p--; {cs = stack[--top]; goto _again;} }
 	break;
 	case 9:
-#line 1189 "upb/json/parser.rl"
+#line 1188 "upb/json/parser.rl"
 	{ {stack[top++] = cs; cs = 19; goto _again;} }
 	break;
 	case 10:
-#line 1191 "upb/json/parser.rl"
+#line 1190 "upb/json/parser.rl"
 	{ p--; {stack[top++] = cs; cs = 27; goto _again;} }
 	break;
 	case 11:
-#line 1196 "upb/json/parser.rl"
+#line 1195 "upb/json/parser.rl"
 	{ start_member(parser); }
 	break;
 	case 12:
-#line 1197 "upb/json/parser.rl"
+#line 1196 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(end_membername(parser)); }
 	break;
 	case 13:
-#line 1200 "upb/json/parser.rl"
+#line 1199 "upb/json/parser.rl"
 	{ end_member(parser); }
 	break;
 	case 14:
-#line 1206 "upb/json/parser.rl"
+#line 1205 "upb/json/parser.rl"
 	{ start_object(parser); }
 	break;
 	case 15:
-#line 1209 "upb/json/parser.rl"
+#line 1208 "upb/json/parser.rl"
 	{ end_object(parser); }
 	break;
 	case 16:
-#line 1215 "upb/json/parser.rl"
+#line 1214 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(start_array(parser)); }
 	break;
 	case 17:
-#line 1219 "upb/json/parser.rl"
+#line 1218 "upb/json/parser.rl"
 	{ end_array(parser); }
 	break;
 	case 18:
-#line 1224 "upb/json/parser.rl"
+#line 1223 "upb/json/parser.rl"
 	{ start_number(parser, p); }
 	break;
 	case 19:
-#line 1225 "upb/json/parser.rl"
+#line 1224 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(end_number(parser, p)); }
 	break;
 	case 20:
-#line 1227 "upb/json/parser.rl"
+#line 1226 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(start_stringval(parser)); }
 	break;
 	case 21:
-#line 1228 "upb/json/parser.rl"
+#line 1227 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(end_stringval(parser)); }
 	break;
 	case 22:
-#line 1230 "upb/json/parser.rl"
+#line 1229 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(parser_putbool(parser, true)); }
 	break;
 	case 23:
-#line 1232 "upb/json/parser.rl"
+#line 1231 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(parser_putbool(parser, false)); }
 	break;
 	case 24:
-#line 1234 "upb/json/parser.rl"
+#line 1233 "upb/json/parser.rl"
 	{ /* null value */ }
 	break;
 	case 25:
-#line 1236 "upb/json/parser.rl"
+#line 1235 "upb/json/parser.rl"
 	{ CHECK_RETURN_TOP(start_subobject(parser)); }
 	break;
 	case 26:
-#line 1237 "upb/json/parser.rl"
+#line 1236 "upb/json/parser.rl"
 	{ end_subobject(parser); }
 	break;
 	case 27:
-#line 1242 "upb/json/parser.rl"
+#line 1241 "upb/json/parser.rl"
 	{ p--; {cs = stack[--top]; goto _again;} }
 	break;
-#line 1514 "upb/json/parser.c"
+#line 1513 "upb/json/parser.c"
 		}
 	}
 
@@ -11811,7 +12947,7 @@ _again:
 	_out: {}
 	}
 
-#line 1269 "upb/json/parser.rl"
+#line 1268 "upb/json/parser.rl"
 
   if (p != pe) {
     upb_status_seterrf(&parser->status, "Parse error at '%.*s'\n", pe - p, p);
@@ -11852,13 +12988,13 @@ static void json_parser_reset(upb_json_parser *p) {
 
   /* Emit Ragel initialization of the parser. */
   
-#line 1568 "upb/json/parser.c"
+#line 1567 "upb/json/parser.c"
 	{
 	cs = json_start;
 	top = 0;
 	}
 
-#line 1309 "upb/json/parser.rl"
+#line 1308 "upb/json/parser.rl"
   p->current_state = cs;
   p->parser_top = top;
   accumulate_clear(p);
@@ -11922,7 +13058,7 @@ static void add_jsonname_table(upb_json_parsermethod *m, const upb_msgdef* md) {
       buf = upb_grealloc(buf, 0, field_len);
       len = field_len;
       len2 = upb_fielddef_getjsonname(f, buf, len);
-      UPB_ASSERT_VAR(len2, len == len2);
+      UPB_ASSERT(len == len2);
     }
     upb_strtable_insert(t, buf, upb_value_constptr(f));
 
@@ -11966,7 +13102,8 @@ upb_json_parser *upb_json_parser_create(upb_env *env,
 
   /* If this fails, uncomment and increase the value in parser.h. */
   /* fprintf(stderr, "%zd\n", upb_env_bytesallocated(env) - size_before); */
-  assert(upb_env_bytesallocated(env) - size_before <= UPB_JSON_PARSER_SIZE);
+  UPB_ASSERT_DEBUGVAR(upb_env_bytesallocated(env) - size_before <=
+                      UPB_JSON_PARSER_SIZE);
   return p;
 }
 
@@ -12054,7 +13191,7 @@ strpc *newstrpc(upb_handlers *h, const upb_fielddef *f,
     ret->len = upb_fielddef_getjsonname(f, NULL, 0);
     ret->ptr = upb_gmalloc(ret->len);
     len = upb_fielddef_getjsonname(f, ret->ptr, ret->len);
-    UPB_ASSERT_VAR(len, len == ret->len);
+    UPB_ASSERT(len == ret->len);
     ret->len--;  /* NULL */
   }
 
@@ -12068,7 +13205,7 @@ static void print_data(
     upb_json_printer *p, const char *buf, unsigned int len) {
   /* TODO: Will need to change if we support pushback from the sink. */
   size_t n = upb_bytessink_putbuf(p->output_, p->subc_, buf, len, NULL);
-  UPB_ASSERT_VAR(n, n == len);
+  UPB_ASSERT(n == len);
 }
 
 static void print_comma(upb_json_printer *p) {
@@ -12418,7 +13555,7 @@ static size_t putbytes(void *closure, const void *handler_data, const char *str,
 
   while (remaining > 2) {
     /* TODO(haberman): handle encoded lengths > sizeof(data) */
-    UPB_ASSERT_VAR(limit, (limit - to) >= 4);
+    UPB_ASSERT((limit - to) >= 4);
 
     to[0] = base64[from[0] >> 2];
     to[1] = base64[((from[0] & 0x3) << 4) | (from[1] >> 4)];
@@ -12622,7 +13759,7 @@ void printer_sethandlers_mapentry(const void *closure, bool preserve_fieldnames,
       upb_handlers_setstring(h, key_field, mapkey_bytes, &empty_attr);
       break;
     default:
-      assert(false);
+      UPB_ASSERT(false);
       break;
   }
 
@@ -12796,7 +13933,8 @@ upb_json_printer *upb_json_printer_create(upb_env *e, const upb_handlers *h,
   upb_sink_reset(&p->input_, h, p);
 
   /* If this fails, increase the value in printer.h. */
-  assert(upb_env_bytesallocated(e) - size_before <= UPB_JSON_PRINTER_SIZE);
+  UPB_ASSERT_DEBUGVAR(upb_env_bytesallocated(e) - size_before <=
+                      UPB_JSON_PRINTER_SIZE);
   return p;
 }
 
diff --git a/ruby/ext/google/protobuf_c/upb.h b/ruby/ext/google/protobuf_c/upb.h
index e8b683bd..6e1e6c6f 100644
--- a/ruby/ext/google/protobuf_c/upb.h
+++ b/ruby/ext/google/protobuf_c/upb.h
@@ -55,14 +55,13 @@
 ** store pointers or integers of at least 32 bits (upb isn't really useful on
 ** systems where sizeof(void*) < 4).
 **
-** The table must be homogeneous (all values of the same type).  In debug
+** The table must be homogenous (all values of the same type).  In debug
 ** mode, we check this on insert and lookup.
 */
 
 #ifndef UPB_TABLE_H_
 #define UPB_TABLE_H_
 
-#include <assert.h>
 #include <stdint.h>
 #include <string.h>
 /*
@@ -118,20 +117,21 @@ template <int N> class InlinedEnvironment;
 #define UPB_NORETURN
 #endif
 
+#if __STDC_VERSION__ >= 199901L || __cplusplus >= 201103L
+/* C99/C++11 versions. */
+#include <stdio.h>
+#define _upb_snprintf snprintf
+#define _upb_vsnprintf vsnprintf
+#define _upb_va_copy(a, b) va_copy(a, b)
+#elif defined __GNUC__
 /* A few hacky workarounds for functions not in C89.
  * For internal use only!
  * TODO(haberman): fix these by including our own implementations, or finding
  * another workaround.
  */
-#ifdef __GNUC__
 #define _upb_snprintf __builtin_snprintf
 #define _upb_vsnprintf __builtin_vsnprintf
 #define _upb_va_copy(a, b) __va_copy(a, b)
-#elif __STDC_VERSION__ >= 199901L
-/* C99 versions. */
-#define _upb_snprintf snprintf
-#define _upb_vsnprintf vsnprintf
-#define _upb_va_copy(a, b) va_copy(a, b)
 #else
 #error Need implementations of [v]snprintf and va_copy
 #endif
@@ -263,10 +263,23 @@ template <int N> class InlinedEnvironment;
 
 #define UPB_UNUSED(var) (void)var
 
-/* For asserting something about a variable when the variable is not used for
- * anything else.  This prevents "unused variable" warnings when compiling in
- * debug mode. */
-#define UPB_ASSERT_VAR(var, predicate) UPB_UNUSED(var); assert(predicate)
+/* UPB_ASSERT(): in release mode, we use the expression without letting it be
+ * evaluated.  This prevents "unused variable" warnings. */
+#ifdef NDEBUG
+#define UPB_ASSERT(expr) do {} while (false && (expr))
+#else
+#define UPB_ASSERT(expr) assert(expr)
+#endif
+
+/* UPB_ASSERT_DEBUGVAR(): assert that uses functions or variables that only
+ * exist in debug mode.  This turns into regular assert. */
+#define UPB_ASSERT_DEBUGVAR(expr) assert(expr)
+
+#ifdef __GNUC__
+#define UPB_UNREACHABLE() do { assert(0); __builtin_unreachable(); } while(0)
+#else
+#define UPB_UNREACHABLE() do { assert(0); } while(0)
+#endif
 
 /* Generic function type. */
 typedef void upb_func();
@@ -501,17 +514,18 @@ struct upb_alloc {
 };
 
 UPB_INLINE void *upb_malloc(upb_alloc *alloc, size_t size) {
-  assert(size > 0);
+  UPB_ASSERT(alloc);
   return alloc->func(alloc, NULL, 0, size);
 }
 
 UPB_INLINE void *upb_realloc(upb_alloc *alloc, void *ptr, size_t oldsize,
                              size_t size) {
-  assert(size > 0);
+  UPB_ASSERT(alloc);
   return alloc->func(alloc, ptr, oldsize, size);
 }
 
 UPB_INLINE void upb_free(upb_alloc *alloc, void *ptr) {
+  assert(alloc);
   alloc->func(alloc, ptr, 0, 0);
 }
 
@@ -560,11 +574,11 @@ UPB_BEGIN_EXTERN_C
 void upb_arena_init(upb_arena *a);
 void upb_arena_init2(upb_arena *a, void *mem, size_t n, upb_alloc *alloc);
 void upb_arena_uninit(upb_arena *a);
-upb_alloc *upb_arena_alloc(upb_arena *a);
 bool upb_arena_addcleanup(upb_arena *a, upb_cleanup_func *func, void *ud);
 size_t upb_arena_bytesallocated(const upb_arena *a);
 void upb_arena_setnextblocksize(upb_arena *a, size_t size);
 void upb_arena_setmaxblocksize(upb_arena *a, size_t size);
+UPB_INLINE upb_alloc *upb_arena_alloc(upb_arena *a) { return (upb_alloc*)a; }
 
 UPB_END_EXTERN_C
 
@@ -795,7 +809,9 @@ typedef enum {
   UPB_CTYPE_CSTR     = 6,
   UPB_CTYPE_PTR      = 7,
   UPB_CTYPE_CONSTPTR = 8,
-  UPB_CTYPE_FPTR     = 9
+  UPB_CTYPE_FPTR     = 9,
+  UPB_CTYPE_FLOAT    = 10,
+  UPB_CTYPE_DOUBLE   = 11
 } upb_ctype_t;
 
 typedef struct {
@@ -854,7 +870,7 @@ UPB_INLINE upb_value _upb_value_val(uint64_t val, upb_ctype_t ctype) {
     return ret; \
   } \
   UPB_INLINE type_t upb_value_get ## name(upb_value val) { \
-    assert(val.ctype == proto_type); \
+    UPB_ASSERT_DEBUGVAR(val.ctype == proto_type); \
     return (type_t)(converter)val.val; \
   }
 
@@ -869,6 +885,29 @@ FUNCS(constptr, constptr,     const void*,  uintptr_t,  UPB_CTYPE_CONSTPTR)
 FUNCS(fptr,     fptr,         upb_func*,    uintptr_t,  UPB_CTYPE_FPTR)
 
 #undef FUNCS
+
+UPB_INLINE void upb_value_setfloat(upb_value *val, float cval) {
+  memcpy(&val->val, &cval, sizeof(cval));
+  SET_TYPE(val->ctype, UPB_CTYPE_FLOAT);
+}
+
+UPB_INLINE void upb_value_setdouble(upb_value *val, double cval) {
+  memcpy(&val->val, &cval, sizeof(cval));
+  SET_TYPE(val->ctype, UPB_CTYPE_DOUBLE);
+}
+
+UPB_INLINE upb_value upb_value_float(float cval) {
+  upb_value ret;
+  upb_value_setfloat(&ret, cval);
+  return ret;
+}
+
+UPB_INLINE upb_value upb_value_double(double cval) {
+  upb_value ret;
+  upb_value_setdouble(&ret, cval);
+  return ret;
+}
+
 #undef SET_TYPE
 
 
@@ -1111,6 +1150,13 @@ UPB_INLINE size_t upb_strtable_count(const upb_strtable *t) {
   return t->t.count;
 }
 
+void upb_inttable_packedsize(const upb_inttable *t, size_t *size);
+void upb_strtable_packedsize(const upb_strtable *t, size_t *size);
+upb_inttable *upb_inttable_pack(const upb_inttable *t, void *p, size_t *ofs,
+                                size_t size);
+upb_strtable *upb_strtable_pack(const upb_strtable *t, void *p, size_t *ofs,
+                                size_t size);
+
 /* Inserts the given key into the hashtable with the given value.  The key must
  * not already exist in the hash table.  For string tables, the key must be
  * NULL-terminated, and the table will make an internal copy of the key.
@@ -1556,7 +1602,7 @@ template <class T> class upb::reffed_ptr {
   reffed_ptr(U* val, const void* ref_donor = NULL)
       : ptr_(upb::upcast(val)) {
     if (ref_donor) {
-      assert(ptr_);
+      UPB_ASSERT(ptr_);
       ptr_->DonateRef(ref_donor, this);
     } else if (ptr_) {
       ptr_->Ref(this);
@@ -1601,12 +1647,12 @@ template <class T> class upb::reffed_ptr {
   }
 
   T& operator*() const {
-    assert(ptr_);
+    UPB_ASSERT(ptr_);
     return *ptr_;
   }
 
   T* operator->() const {
-    assert(ptr_);
+    UPB_ASSERT(ptr_);
     return ptr_;
   }
 
@@ -1657,6 +1703,7 @@ class FieldDef;
 class FileDef;
 class MessageDef;
 class OneofDef;
+class SymbolTable;
 }
 #endif
 
@@ -1665,6 +1712,8 @@ UPB_DECLARE_DERIVED_TYPE(upb::OneofDef, upb::RefCounted, upb_oneofdef,
                          upb_refcounted)
 UPB_DECLARE_DERIVED_TYPE(upb::FileDef, upb::RefCounted, upb_filedef,
                          upb_refcounted)
+UPB_DECLARE_TYPE(upb::SymbolTable, upb_symtab)
+
 
 /* The maximum message depth that the type graph can have.  This is a resource
  * limit for the C stack since we sometimes need to recursively traverse the
@@ -1698,8 +1747,6 @@ class upb::Def {
  public:
   typedef upb_deftype_t Type;
 
-  Def* Dup(const void *owner) const;
-
   /* upb::RefCounted methods like Ref()/Unref(). */
   UPB_REFCOUNTED_CPPMETHODS
 
@@ -1745,9 +1792,6 @@ class upb::Def {
 
 UPB_BEGIN_EXTERN_C
 
-/* Native C API. */
-upb_def *upb_def_dup(const upb_def *def, const void *owner);
-
 /* Include upb_refcounted methods like upb_def_ref()/upb_def_unref(). */
 UPB_REFCOUNTED_CMETHODS(upb_def, upb_def_upcast)
 
@@ -1808,7 +1852,7 @@ UPB_END_EXTERN_C
     return (upb_##lower *)def;                                             \
   }                                                                        \
   UPB_INLINE const upb_##lower *upb_downcast_##lower(const upb_def *def) { \
-    assert(upb_def_type(def) == UPB_DEF_##upper);                          \
+    UPB_ASSERT(upb_def_type(def) == UPB_DEF_##upper);                          \
     return (const upb_##lower *)def;                                       \
   }                                                                        \
   UPB_INLINE upb_##lower *upb_dyncast_##lower##_mutable(upb_def *def) {    \
@@ -1844,15 +1888,19 @@ UPB_DECLARE_DEF_TYPE(upb::EnumDef, enumdef, ENUM)
  * types defined in descriptor.proto, which gives INT32 and SINT32 separate
  * types (we distinguish the two with the "integer encoding" enum below). */
 typedef enum {
-  UPB_TYPE_FLOAT    = 1,
-  UPB_TYPE_DOUBLE   = 2,
-  UPB_TYPE_BOOL     = 3,
-  UPB_TYPE_STRING   = 4,
-  UPB_TYPE_BYTES    = 5,
-  UPB_TYPE_MESSAGE  = 6,
-  UPB_TYPE_ENUM     = 7,  /* Enum values are int32. */
-  UPB_TYPE_INT32    = 8,
-  UPB_TYPE_UINT32   = 9,
+  /* Types stored in 1 byte. */
+  UPB_TYPE_BOOL     = 1,
+  /* Types stored in 4 bytes. */
+  UPB_TYPE_FLOAT    = 2,
+  UPB_TYPE_INT32    = 3,
+  UPB_TYPE_UINT32   = 4,
+  UPB_TYPE_ENUM     = 5,  /* Enum values are int32. */
+  /* Types stored as pointers (probably 4 or 8 bytes). */
+  UPB_TYPE_STRING   = 6,
+  UPB_TYPE_BYTES    = 7,
+  UPB_TYPE_MESSAGE  = 8,
+  /* Types stored as 8 bytes. */
+  UPB_TYPE_DOUBLE   = 9,
   UPB_TYPE_INT64    = 10,
   UPB_TYPE_UINT64   = 11
 } upb_fieldtype_t;
@@ -1933,13 +1981,6 @@ class upb::FieldDef {
   /* Returns NULL if memory allocation failed. */
   static reffed_ptr<FieldDef> New();
 
-  /* Duplicates the given field, returning NULL if memory allocation failed.
-   * When a fielddef is duplicated, the subdef (if any) is made symbolic if it
-   * wasn't already.  If the subdef is set but has no name (which is possible
-   * since msgdefs are not required to have a name) the new fielddef's subdef
-   * will be unset. */
-  FieldDef* Dup(const void* owner) const;
-
   /* upb::RefCounted methods like Ref()/Unref(). */
   UPB_REFCOUNTED_CPPMETHODS
 
@@ -2026,16 +2067,10 @@ class upb::FieldDef {
   bool IsPrimitive() const;
   bool IsMap() const;
 
-  /* Whether this field must be able to explicitly represent presence:
+  /* Returns whether this field explicitly represents presence.
    *
-   * * This is always false for repeated fields (an empty repeated field is
-   *   equivalent to a repeated field with zero entries).
-   *
-   * * This is always true for submessages.
-   *
-   * * For other fields, it depends on the message (see
-   *   MessageDef::SetPrimitivesHavePresence())
-   */
+   * For proto2 messages: Returns true for any scalar (non-repeated) field.
+   * For proto3 messages: Returns true for scalar submessage or oneof fields. */
   bool HasPresence() const;
 
   /* How integers are encoded.  Only meaningful for integer types.
@@ -2194,7 +2229,6 @@ UPB_BEGIN_EXTERN_C
 
 /* Native C API. */
 upb_fielddef *upb_fielddef_new(const void *owner);
-upb_fielddef *upb_fielddef_dup(const upb_fielddef *f, const void *owner);
 
 /* Include upb_refcounted methods like upb_fielddef_ref(). */
 UPB_REFCOUNTED_CMETHODS(upb_fielddef, upb_fielddef_upcast2)
@@ -2404,16 +2438,6 @@ class upb::MessageDef {
     return FindOneofByName(str.c_str(), str.size());
   }
 
-  /* Returns a new msgdef that is a copy of the given msgdef (and a copy of all
-   * the fields) but with any references to submessages broken and replaced
-   * with just the name of the submessage.  Returns NULL if memory allocation
-   * failed.
-   *
-   * TODO(haberman): which is more useful, keeping fields resolved or
-   * unresolving them?  If there's no obvious answer, Should this functionality
-   * just be moved into symtab.c? */
-  MessageDef* Dup(const void* owner) const;
-
   /* Is this message a map entry? */
   void setmapentry(bool map_entry);
   bool mapentry() const;
@@ -2547,7 +2571,6 @@ UPB_REFCOUNTED_CMETHODS(upb_msgdef, upb_msgdef_upcast2)
 
 bool upb_msgdef_freeze(upb_msgdef *m, upb_status *status);
 
-upb_msgdef *upb_msgdef_dup(const upb_msgdef *m, const void *owner);
 const char *upb_msgdef_fullname(const upb_msgdef *m);
 const char *upb_msgdef_name(const upb_msgdef *m);
 int upb_msgdef_numoneofs(const upb_msgdef *m);
@@ -2697,10 +2720,6 @@ class upb::EnumDef {
    * first one that was added. */
   const char* FindValueByNumber(int32_t num) const;
 
-  /* Returns a new EnumDef with all the same values.  The new EnumDef will be
-   * owned by the given owner. */
-  EnumDef* Dup(const void* owner) const;
-
   /* Iteration over name/value pairs.  The order is undefined.
    * Adding an enum val invalidates any iterators.
    *
@@ -2728,7 +2747,6 @@ UPB_BEGIN_EXTERN_C
 
 /* Native C API. */
 upb_enumdef *upb_enumdef_new(const void *owner);
-upb_enumdef *upb_enumdef_dup(const upb_enumdef *e, const void *owner);
 
 /* Include upb_refcounted methods like upb_enumdef_ref(). */
 UPB_REFCOUNTED_CMETHODS(upb_enumdef, upb_enumdef_upcast2)
@@ -2773,6 +2791,7 @@ int32_t upb_enum_iter_number(upb_enum_iter *iter);
 
 UPB_END_EXTERN_C
 
+
 /* upb::OneofDef **************************************************************/
 
 typedef upb_inttable_iter upb_oneof_iter;
@@ -2837,10 +2856,6 @@ class upb::OneofDef {
   /* Looks up by tag number. */
   const FieldDef* FindFieldByNumber(uint32_t num) const;
 
-  /* Returns a new OneofDef with all the same fields. The OneofDef will be owned
-   * by the given owner. */
-  OneofDef* Dup(const void* owner) const;
-
   /* Iteration over fields.  The order is undefined. */
   class iterator : public std::iterator<std::forward_iterator_tag, FieldDef*> {
    public:
@@ -2886,16 +2901,16 @@ UPB_BEGIN_EXTERN_C
 
 /* Native C API. */
 upb_oneofdef *upb_oneofdef_new(const void *owner);
-upb_oneofdef *upb_oneofdef_dup(const upb_oneofdef *o, const void *owner);
 
 /* Include upb_refcounted methods like upb_oneofdef_ref(). */
 UPB_REFCOUNTED_CMETHODS(upb_oneofdef, upb_oneofdef_upcast)
 
 const char *upb_oneofdef_name(const upb_oneofdef *o);
-bool upb_oneofdef_setname(upb_oneofdef *o, const char *name, upb_status *s);
-
 const upb_msgdef *upb_oneofdef_containingtype(const upb_oneofdef *o);
 int upb_oneofdef_numfields(const upb_oneofdef *o);
+uint32_t upb_oneofdef_index(const upb_oneofdef *o);
+
+bool upb_oneofdef_setname(upb_oneofdef *o, const char *name, upb_status *s);
 bool upb_oneofdef_addfield(upb_oneofdef *o, upb_fielddef *f,
                            const void *ref_donor,
                            upb_status *s);
@@ -3039,19 +3054,163 @@ UPB_INLINE upb_def *upb_filedef_mutabledef(upb_filedef *f, int i) {
 
 UPB_END_EXTERN_C
 
+typedef struct {
+ UPB_PRIVATE_FOR_CPP
+  upb_strtable_iter iter;
+  upb_deftype_t type;
+} upb_symtab_iter;
+
+#ifdef __cplusplus
+
+/* Non-const methods in upb::SymbolTable are NOT thread-safe. */
+class upb::SymbolTable {
+ public:
+  /* Returns a new symbol table with a single ref owned by "owner."
+   * Returns NULL if memory allocation failed. */
+  static SymbolTable* New();
+  static void Free(upb::SymbolTable* table);
+
+  /* For all lookup functions, the returned pointer is not owned by the
+   * caller; it may be invalidated by any non-const call or unref of the
+   * SymbolTable!  To protect against this, take a ref if desired. */
+
+  /* Freezes the symbol table: prevents further modification of it.
+   * After the Freeze() operation is successful, the SymbolTable must only be
+   * accessed via a const pointer.
+   *
+   * Unlike with upb::MessageDef/upb::EnumDef/etc, freezing a SymbolTable is not
+   * a necessary step in using a SymbolTable.  If you have no need for it to be
+   * immutable, there is no need to freeze it ever.  However sometimes it is
+   * useful, and SymbolTables that are statically compiled into the binary are
+   * always frozen by nature. */
+  void Freeze();
+
+  /* Resolves the given symbol using the rules described in descriptor.proto,
+   * namely:
+   *
+   *    If the name starts with a '.', it is fully-qualified.  Otherwise,
+   *    C++-like scoping rules are used to find the type (i.e. first the nested
+   *    types within this message are searched, then within the parent, on up
+   *    to the root namespace).
+   *
+   * If not found, returns NULL. */
+  const Def* Resolve(const char* base, const char* sym) const;
+
+  /* Finds an entry in the symbol table with this exact name.  If not found,
+   * returns NULL. */
+  const Def* Lookup(const char *sym) const;
+  const MessageDef* LookupMessage(const char *sym) const;
+  const EnumDef* LookupEnum(const char *sym) const;
+
+  /* TODO: introduce a C++ iterator, but make it nice and templated so that if
+   * you ask for an iterator of MessageDef the iterated elements are strongly
+   * typed as MessageDef*. */
+
+  /* Adds the given mutable defs to the symtab, resolving all symbols (including
+   * enum default values) and finalizing the defs.  Only one def per name may be
+   * in the list, and the defs may not duplicate any name already in the symtab.
+   * All defs must have a name -- anonymous defs are not allowed.  Anonymous
+   * defs can still be frozen by calling upb_def_freeze() directly.
+   *
+   * The entire operation either succeeds or fails.  If the operation fails,
+   * the symtab is unchanged, false is returned, and status indicates the
+   * error.  The caller passes a ref on all defs to the symtab (even if the
+   * operation fails).
+   *
+   * TODO(haberman): currently failure will leave the symtab unchanged, but may
+   * leave the defs themselves partially resolved.  Does this matter?  If so we
+   * could do a prepass that ensures that all symbols are resolvable and bail
+   * if not, so we don't mutate anything until we know the operation will
+   * succeed. */
+  bool Add(Def*const* defs, size_t n, void* ref_donor, Status* status);
+
+  bool Add(const std::vector<Def*>& defs, void *owner, Status* status) {
+    return Add((Def*const*)&defs[0], defs.size(), owner, status);
+  }
+
+  /* Resolves all subdefs for messages in this file and attempts to freeze the
+   * file.  If this succeeds, adds all the symbols to this SymbolTable
+   * (replacing any existing ones with the same names). */
+  bool AddFile(FileDef* file, Status* s);
+
+ private:
+  UPB_DISALLOW_POD_OPS(SymbolTable, upb::SymbolTable)
+};
+
+#endif  /* __cplusplus */
+
+UPB_BEGIN_EXTERN_C
+
+/* Native C API. */
+
+upb_symtab *upb_symtab_new();
+void upb_symtab_free(upb_symtab* s);
+const upb_def *upb_symtab_resolve(const upb_symtab *s, const char *base,
+                                  const char *sym);
+const upb_def *upb_symtab_lookup(const upb_symtab *s, const char *sym);
+const upb_msgdef *upb_symtab_lookupmsg(const upb_symtab *s, const char *sym);
+const upb_enumdef *upb_symtab_lookupenum(const upb_symtab *s, const char *sym);
+bool upb_symtab_add(upb_symtab *s, upb_def *const*defs, size_t n,
+                    void *ref_donor, upb_status *status);
+bool upb_symtab_addfile(upb_symtab *s, upb_filedef *file, upb_status* status);
+
+/* upb_symtab_iter i;
+ * for(upb_symtab_begin(&i, s, type); !upb_symtab_done(&i);
+ *     upb_symtab_next(&i)) {
+ *   const upb_def *def = upb_symtab_iter_def(&i);
+ *    // ...
+ * }
+ *
+ * For C we don't have separate iterators for const and non-const.
+ * It is the caller's responsibility to cast the upb_fielddef* to
+ * const if the upb_msgdef* is const. */
+void upb_symtab_begin(upb_symtab_iter *iter, const upb_symtab *s,
+                      upb_deftype_t type);
+void upb_symtab_next(upb_symtab_iter *iter);
+bool upb_symtab_done(const upb_symtab_iter *iter);
+const upb_def *upb_symtab_iter_def(const upb_symtab_iter *iter);
+
+UPB_END_EXTERN_C
+
+#ifdef __cplusplus
+/* C++ inline wrappers. */
+namespace upb {
+inline SymbolTable* SymbolTable::New() {
+  return upb_symtab_new();
+}
+inline void SymbolTable::Free(SymbolTable* s) {
+  upb_symtab_free(s);
+}
+inline const Def *SymbolTable::Resolve(const char *base,
+                                       const char *sym) const {
+  return upb_symtab_resolve(this, base, sym);
+}
+inline const Def* SymbolTable::Lookup(const char *sym) const {
+  return upb_symtab_lookup(this, sym);
+}
+inline const MessageDef *SymbolTable::LookupMessage(const char *sym) const {
+  return upb_symtab_lookupmsg(this, sym);
+}
+inline bool SymbolTable::Add(
+    Def*const* defs, size_t n, void* ref_donor, Status* status) {
+  return upb_symtab_add(this, (upb_def*const*)defs, n, ref_donor, status);
+}
+inline bool SymbolTable::AddFile(FileDef* file, Status* s) {
+  return upb_symtab_addfile(this, file, s);
+}
+}  /* namespace upb */
+#endif
+
 #ifdef __cplusplus
 
 UPB_INLINE const char* upb_safecstr(const std::string& str) {
-  assert(str.size() == std::strlen(str.c_str()));
+  UPB_ASSERT(str.size() == std::strlen(str.c_str()));
   return str.c_str();
 }
 
 /* Inline C++ wrappers. */
 namespace upb {
 
-inline Def* Def::Dup(const void* owner) const {
-  return upb_def_dup(this, owner);
-}
 inline Def::Type Def::def_type() const { return upb_def_type(this); }
 inline const char* Def::full_name() const { return upb_def_fullname(this); }
 inline const char* Def::name() const { return upb_def_name(this); }
@@ -3081,19 +3240,19 @@ inline bool FieldDef::CheckIntegerFormat(int32_t val) {
   return upb_fielddef_checkintfmt(val);
 }
 inline FieldDef::Type FieldDef::ConvertType(int32_t val) {
-  assert(CheckType(val));
+  UPB_ASSERT(CheckType(val));
   return static_cast<FieldDef::Type>(val);
 }
 inline FieldDef::Label FieldDef::ConvertLabel(int32_t val) {
-  assert(CheckLabel(val));
+  UPB_ASSERT(CheckLabel(val));
   return static_cast<FieldDef::Label>(val);
 }
 inline FieldDef::DescriptorType FieldDef::ConvertDescriptorType(int32_t val) {
-  assert(CheckDescriptorType(val));
+  UPB_ASSERT(CheckDescriptorType(val));
   return static_cast<FieldDef::DescriptorType>(val);
 }
 inline FieldDef::IntegerFormat FieldDef::ConvertIntegerFormat(int32_t val) {
-  assert(CheckIntegerFormat(val));
+  UPB_ASSERT(CheckIntegerFormat(val));
   return static_cast<FieldDef::IntegerFormat>(val);
 }
 
@@ -3101,9 +3260,6 @@ inline reffed_ptr<FieldDef> FieldDef::New() {
   upb_fielddef *f = upb_fielddef_new(&f);
   return reffed_ptr<FieldDef>(f, &f);
 }
-inline FieldDef* FieldDef::Dup(const void* owner) const {
-  return upb_fielddef_dup(this, owner);
-}
 inline const char* FieldDef::full_name() const {
   return upb_fielddef_fullname(this);
 }
@@ -3343,9 +3499,6 @@ inline const OneofDef* MessageDef::FindOneofByName(const char* name,
                                                    size_t len) const {
   return upb_msgdef_ntoo(this, name, len);
 }
-inline MessageDef* MessageDef::Dup(const void *owner) const {
-  return upb_msgdef_dup(this, owner);
-}
 inline void MessageDef::setmapentry(bool map_entry) {
   upb_msgdef_setmapentry(this, map_entry);
 }
@@ -3515,9 +3668,6 @@ inline bool EnumDef::FindValueByName(const char* name, int32_t *num) const {
 inline const char* EnumDef::FindValueByNumber(int32_t num) const {
   return upb_enumdef_iton(this, num);
 }
-inline EnumDef* EnumDef::Dup(const void* owner) const {
-  return upb_enumdef_dup(this, owner);
-}
 
 inline EnumDef::Iterator::Iterator(const EnumDef* e) {
   upb_enum_begin(&iter_, e);
@@ -3824,6 +3974,7 @@ extern const struct upb_refcounted_vtbl upb_enumdef_vtbl;
 struct upb_oneofdef {
   upb_refcounted base;
 
+  uint32_t index;  /* Index within oneofs. */
   const char *name;
   upb_strtable ntof;
   upb_inttable itof;
@@ -3833,7 +3984,7 @@ struct upb_oneofdef {
 extern const struct upb_refcounted_vtbl upb_oneofdef_vtbl;
 
 #define UPB_ONEOFDEF_INIT(name, ntof, itof, refs, ref2s) \
-  { UPB_REFCOUNT_INIT(&upb_oneofdef_vtbl, refs, ref2s), name, ntof, itof }
+  { UPB_REFCOUNT_INIT(&upb_oneofdef_vtbl, refs, ref2s), 0, name, ntof, itof }
 
 
 /* upb_symtab *****************************************************************/
@@ -4469,7 +4620,7 @@ template <class T> class Handler {
   void AddCleanup(Handlers* h) const {
     if (cleanup_func_) {
       bool ok = h->AddCleanup(cleanup_data_, cleanup_func_);
-      UPB_ASSERT_VAR(ok, ok);
+      UPB_ASSERT(ok);
     }
   }
 
@@ -5489,7 +5640,7 @@ struct ConvertParams<BoundFunc5<R, P1, P2, P3, P4, P5, F, I>, T> {
   inline bool Handlers::SetValueHandler<vtype>(                                \
       const FieldDef *f,                                                       \
       const Handlers::utype ## Handler& handler) {                             \
-    assert(!handler.registered_);                                              \
+    UPB_ASSERT(!handler.registered_);                                              \
     handler.AddCleanup(this);                                                  \
     handler.registered_ = true;                                                \
     return upb_handlers_set##ltype(this, f, handler.handler_, &handler.attr_); \
@@ -5601,7 +5752,7 @@ inline Handler<T>::Handler(F func)
 
 template <class T>
 inline Handler<T>::~Handler() {
-  assert(registered_);
+  UPB_ASSERT(registered_);
 }
 
 inline HandlerAttributes::HandlerAttributes() { upb_handlerattr_init(this); }
@@ -5687,63 +5838,63 @@ inline bool Handlers::AddCleanup(void *p, upb_handlerfree *func) {
 }
 inline bool Handlers::SetStartMessageHandler(
     const Handlers::StartMessageHandler &handler) {
-  assert(!handler.registered_);
+  UPB_ASSERT(!handler.registered_);
   handler.registered_ = true;
   handler.AddCleanup(this);
   return upb_handlers_setstartmsg(this, handler.handler_, &handler.attr_);
 }
 inline bool Handlers::SetEndMessageHandler(
     const Handlers::EndMessageHandler &handler) {
-  assert(!handler.registered_);
+  UPB_ASSERT(!handler.registered_);
   handler.registered_ = true;
   handler.AddCleanup(this);
   return upb_handlers_setendmsg(this, handler.handler_, &handler.attr_);
 }
 inline bool Handlers::SetStartStringHandler(const FieldDef *f,
                                             const StartStringHandler &handler) {
-  assert(!handler.registered_);
+  UPB_ASSERT(!handler.registered_);
   handler.registered_ = true;
   handler.AddCleanup(this);
   return upb_handlers_setstartstr(this, f, handler.handler_, &handler.attr_);
 }
 inline bool Handlers::SetEndStringHandler(const FieldDef *f,
                                           const EndFieldHandler &handler) {
-  assert(!handler.registered_);
+  UPB_ASSERT(!handler.registered_);
   handler.registered_ = true;
   handler.AddCleanup(this);
   return upb_handlers_setendstr(this, f, handler.handler_, &handler.attr_);
 }
 inline bool Handlers::SetStringHandler(const FieldDef *f,
                                        const StringHandler& handler) {
-  assert(!handler.registered_);
+  UPB_ASSERT(!handler.registered_);
   handler.registered_ = true;
   handler.AddCleanup(this);
   return upb_handlers_setstring(this, f, handler.handler_, &handler.attr_);
 }
 inline bool Handlers::SetStartSequenceHandler(
     const FieldDef *f, const StartFieldHandler &handler) {
-  assert(!handler.registered_);
+  UPB_ASSERT(!handler.registered_);
   handler.registered_ = true;
   handler.AddCleanup(this);
   return upb_handlers_setstartseq(this, f, handler.handler_, &handler.attr_);
 }
 inline bool Handlers::SetStartSubMessageHandler(
     const FieldDef *f, const StartFieldHandler &handler) {
-  assert(!handler.registered_);
+  UPB_ASSERT(!handler.registered_);
   handler.registered_ = true;
   handler.AddCleanup(this);
   return upb_handlers_setstartsubmsg(this, f, handler.handler_, &handler.attr_);
 }
 inline bool Handlers::SetEndSubMessageHandler(const FieldDef *f,
                                               const EndFieldHandler &handler) {
-  assert(!handler.registered_);
+  UPB_ASSERT(!handler.registered_);
   handler.registered_ = true;
   handler.AddCleanup(this);
   return upb_handlers_setendsubmsg(this, f, handler.handler_, &handler.attr_);
 }
 inline bool Handlers::SetEndSequenceHandler(const FieldDef *f,
                                             const EndFieldHandler &handler) {
-  assert(!handler.registered_);
+  UPB_ASSERT(!handler.registered_);
   handler.registered_ = true;
   handler.AddCleanup(this);
   return upb_handlers_setendseq(this, f, handler.handler_, &handler.attr_);
@@ -5820,12 +5971,14 @@ inline BytesHandler::~BytesHandler() {}
 
 #ifdef __cplusplus
 namespace upb {
+class BufferSink;
 class BufferSource;
 class BytesSink;
 class Sink;
 }
 #endif
 
+UPB_DECLARE_TYPE(upb::BufferSink, upb_bufsink)
 UPB_DECLARE_TYPE(upb::BufferSource, upb_bufsrc)
 UPB_DECLARE_TYPE(upb::BytesSink, upb_bytessink)
 UPB_DECLARE_TYPE(upb::Sink, upb_sink)
@@ -6012,6 +6165,13 @@ struct upb_bufsrc {
 
 UPB_BEGIN_EXTERN_C
 
+/* A class for accumulating output string data in a flat buffer. */
+
+upb_bufsink *upb_bufsink_new(upb_env *env);
+void upb_bufsink_free(upb_bufsink *sink);
+upb_bytessink *upb_bufsink_sink(upb_bufsink *sink);
+const char *upb_bufsink_getdata(const upb_bufsink *sink, size_t *len);
+
 /* Inline definitions. */
 
 UPB_INLINE void upb_bytessink_reset(upb_bytessink *s, const upb_byteshandler *h,
@@ -6061,23 +6221,7 @@ UPB_INLINE bool upb_bytessink_end(upb_bytessink *s) {
                  &s->handler->table[UPB_ENDSTR_SELECTOR].attr));
 }
 
-UPB_INLINE bool upb_bufsrc_putbuf(const char *buf, size_t len,
-                                  upb_bytessink *sink) {
-  void *subc;
-  bool ret;
-  upb_bufhandle handle;
-  upb_bufhandle_init(&handle);
-  upb_bufhandle_setbuf(&handle, buf, 0);
-  ret = upb_bytessink_start(sink, len, &subc);
-  if (ret && len != 0) {
-    ret = (upb_bytessink_putbuf(sink, subc, buf, len, &handle) >= len);
-  }
-  if (ret) {
-    ret = upb_bytessink_end(sink);
-  }
-  upb_bufhandle_uninit(&handle);
-  return ret;
-}
+bool upb_bufsrc_putbuf(const char *buf, size_t len, upb_bytessink *sink);
 
 #define PUTVAL(type, ctype)                                                    \
   UPB_INLINE bool upb_sink_put##type(upb_sink *s, upb_selector_t sel,          \
@@ -6325,267 +6469,407 @@ inline bool BufferSource::PutBuffer(const char *buf, size_t len,
 
 #endif
 /*
-** For handlers that do very tiny, very simple operations, the function call
-** overhead of calling a handler can be significant.  This file allows the
-** user to define handlers that do something very simple like store the value
-** to memory and/or set a hasbit.  JIT compilers can then special-case these
-** handlers and emit specialized code for them instead of actually calling the
-** handler.
+** upb::Message is a representation for protobuf messages.
 **
-** The functionality is very simple/limited right now but may expand to be able
-** to call another function.
-*/
-
-#ifndef UPB_SHIM_H
-#define UPB_SHIM_H
+** However it differs from other common representations like
+** google::protobuf::Message in one key way: it does not prescribe any
+** ownership between messages and submessages, and it relies on the
+** client to delete each message/submessage/array/map at the appropriate
+** time.
+**
+** A client can access a upb::Message without knowing anything about
+** ownership semantics, but to create or mutate a message a user needs
+** to implement the memory management themselves.
+**
+** Currently all messages, arrays, and maps store a upb_alloc* internally.
+** Mutating operations use this when they require dynamically-allocated
+** memory.  We could potentially eliminate this size overhead later by
+** letting the user flip a bit on the factory that prevents this from
+** being stored.  The user would then need to use separate functions where
+** the upb_alloc* is passed explicitly.  However for handlers to populate
+** such structures, they would need a place to store this upb_alloc* during
+** parsing; upb_handlers don't currently have a good way to accommodate this.
+**
+** TODO: UTF-8 checking?
+**/
 
+#ifndef UPB_MSG_H_
+#define UPB_MSG_H_
 
-typedef struct {
-  size_t offset;
-  int32_t hasbit;
-} upb_shim_data;
 
 #ifdef __cplusplus
 
 namespace upb {
+class Array;
+class Map;
+class MapIterator;
+class MessageFactory;
+class MessageLayout;
+class Visitor;
+class VisitorPlan;
+}
 
-struct Shim {
-  typedef upb_shim_data Data;
+#endif
 
-  /* Sets a handler for the given field that writes the value to the given
-   * offset and, if hasbit >= 0, sets a bit at the given bit offset.  Returns
-   * true if the handler was set successfully. */
-  static bool Set(Handlers *h, const FieldDef *f, size_t ofs, int32_t hasbit);
+UPB_DECLARE_TYPE(upb::MessageFactory, upb_msgfactory)
+UPB_DECLARE_TYPE(upb::MessageLayout, upb_msglayout)
+UPB_DECLARE_TYPE(upb::Array, upb_array)
+UPB_DECLARE_TYPE(upb::Map, upb_map)
+UPB_DECLARE_TYPE(upb::MapIterator, upb_mapiter)
+UPB_DECLARE_TYPE(upb::Visitor, upb_visitor)
+UPB_DECLARE_TYPE(upb::VisitorPlan, upb_visitorplan)
 
-  /* If this handler is a shim, returns the corresponding upb::Shim::Data and
-   * stores the type in "type".  Otherwise returns NULL. */
-  static const Data* GetData(const Handlers* h, Handlers::Selector s,
-                             FieldDef::Type* type);
-};
+/* TODO(haberman): C++ accessors */
 
-}  /* namespace upb */
+UPB_BEGIN_EXTERN_C
 
-#endif
+typedef void upb_msg;
 
-UPB_BEGIN_EXTERN_C
 
-/* C API. */
-bool upb_shim_set(upb_handlers *h, const upb_fielddef *f, size_t offset,
-                  int32_t hasbit);
-const upb_shim_data *upb_shim_getdata(const upb_handlers *h, upb_selector_t s,
-                                      upb_fieldtype_t *type);
+/** upb_msglayout *************************************************************/
 
-UPB_END_EXTERN_C
+/* upb_msglayout represents the memory layout of a given upb_msgdef.  You get
+ * instances of this from a upb_msgfactory, and the factory always owns the
+ * msglayout. */
 
-#ifdef __cplusplus
-/* C++ Wrappers. */
-namespace upb {
-inline bool Shim::Set(Handlers* h, const FieldDef* f, size_t ofs,
-                      int32_t hasbit) {
-  return upb_shim_set(h, f, ofs, hasbit);
-}
-inline const Shim::Data* Shim::GetData(const Handlers* h, Handlers::Selector s,
-                                       FieldDef::Type* type) {
-  return upb_shim_getdata(h, s, type);
-}
-}  /* namespace upb */
-#endif
+/* Gets the factory for this layout */
+upb_msgfactory *upb_msglayout_factory(const upb_msglayout *l);
 
-#endif  /* UPB_SHIM_H */
-/*
-** upb::SymbolTable (upb_symtab)
-**
-** A symtab (symbol table) stores a name->def map of upb_defs.  Clients could
-** always create such tables themselves, but upb_symtab has logic for resolving
-** symbolic references, and in particular, for keeping a whole set of consistent
-** defs when replacing some subset of those defs.  This logic is nontrivial.
-**
-** This is a mixed C/C++ interface that offers a full API to both languages.
-** See the top-level README for more information.
-*/
+/* Get the msglayout for a submessage.  This requires that this field is a
+ * submessage, ie. upb_fielddef_issubmsg(upb_msglayout_msgdef(l)) == true.
+ *
+ * Since map entry messages don't have layouts, if upb_fielddef_ismap(f) == true
+ * then this function will return the layout for the map's value.  It requires
+ * that the value type of the map field is a submessage. */
+const upb_msglayout *upb_msglayout_sublayout(const upb_msglayout *l,
+                                             const upb_fielddef *f);
 
-#ifndef UPB_SYMTAB_H_
-#define UPB_SYMTAB_H_
+/* Returns the msgdef for this msglayout. */
+const upb_msgdef *upb_msglayout_msgdef(const upb_msglayout *l);
 
 
-#ifdef __cplusplus
-#include <vector>
-namespace upb { class SymbolTable; }
-#endif
+/** upb_visitor ***************************************************************/
 
-UPB_DECLARE_DERIVED_TYPE(upb::SymbolTable, upb::RefCounted,
-                         upb_symtab, upb_refcounted)
+/* upb_visitor will visit all the fields of a message and its submessages.  It
+ * uses a upb_visitorplan which you can obtain from a upb_msgfactory. */
 
-typedef struct {
- UPB_PRIVATE_FOR_CPP
-  upb_strtable_iter iter;
-  upb_deftype_t type;
-} upb_symtab_iter;
+upb_visitor *upb_visitor_create(upb_env *e, const upb_visitorplan *vp,
+                                upb_sink *output);
+bool upb_visitor_visitmsg(upb_visitor *v, const upb_msg *msg);
 
-#ifdef __cplusplus
 
-/* Non-const methods in upb::SymbolTable are NOT thread-safe. */
-class upb::SymbolTable {
- public:
-  /* Returns a new symbol table with a single ref owned by "owner."
-   * Returns NULL if memory allocation failed. */
-  static reffed_ptr<SymbolTable> New();
+/** upb_msgfactory ************************************************************/
 
-  /* Include RefCounted base methods. */
-  UPB_REFCOUNTED_CPPMETHODS
+/* A upb_msgfactory contains a cache of upb_msglayout, upb_handlers, and
+ * upb_visitorplan objects.  These are the objects necessary to represent,
+ * populate, and and visit upb_msg objects.
+ *
+ * These caches are all populated by upb_msgdef, and lazily created on demand.
+ */
 
-  /* For all lookup functions, the returned pointer is not owned by the
-   * caller; it may be invalidated by any non-const call or unref of the
-   * SymbolTable!  To protect against this, take a ref if desired. */
+/* Creates and destroys a msgfactory, respectively.  The messages for this
+ * msgfactory must come from |symtab| (which should outlive the msgfactory). */
+upb_msgfactory *upb_msgfactory_new(const upb_symtab *symtab);
+void upb_msgfactory_free(upb_msgfactory *f);
 
-  /* Freezes the symbol table: prevents further modification of it.
-   * After the Freeze() operation is successful, the SymbolTable must only be
-   * accessed via a const pointer.
-   *
-   * Unlike with upb::MessageDef/upb::EnumDef/etc, freezing a SymbolTable is not
-   * a necessary step in using a SymbolTable.  If you have no need for it to be
-   * immutable, there is no need to freeze it ever.  However sometimes it is
-   * useful, and SymbolTables that are statically compiled into the binary are
-   * always frozen by nature. */
-  void Freeze();
+const upb_symtab *upb_msgfactory_symtab(const upb_msgfactory *f);
 
-  /* Resolves the given symbol using the rules described in descriptor.proto,
-   * namely:
-   *
-   *    If the name starts with a '.', it is fully-qualified.  Otherwise,
-   *    C++-like scoping rules are used to find the type (i.e. first the nested
-   *    types within this message are searched, then within the parent, on up
-   *    to the root namespace).
-   *
-   * If not found, returns NULL. */
-  const Def* Resolve(const char* base, const char* sym) const;
+/* The functions to get cached objects, lazily creating them on demand.  These
+ * all require:
+ *
+ * - m is in upb_msgfactory_symtab(f)
+ * - upb_msgdef_mapentry(m) == false (since map messages can't have layouts).
+ *
+ * The returned objects will live for as long as the msgfactory does.
+ *
+ * TODO(haberman): consider making this thread-safe and take a const
+ * upb_msgfactory. */
+const upb_msglayout *upb_msgfactory_getlayout(upb_msgfactory *f,
+                                              const upb_msgdef *m);
+const upb_handlers *upb_msgfactory_getmergehandlers(upb_msgfactory *f,
+                                                    const upb_msgdef *m);
+const upb_visitorplan *upb_msgfactory_getvisitorplan(upb_msgfactory *f,
+                                                     const upb_handlers *h);
 
-  /* Finds an entry in the symbol table with this exact name.  If not found,
-   * returns NULL. */
-  const Def* Lookup(const char *sym) const;
-  const MessageDef* LookupMessage(const char *sym) const;
-  const EnumDef* LookupEnum(const char *sym) const;
 
-  /* TODO: introduce a C++ iterator, but make it nice and templated so that if
-   * you ask for an iterator of MessageDef the iterated elements are strongly
-   * typed as MessageDef*. */
+/** upb_msgval ****************************************************************/
 
-  /* Adds the given mutable defs to the symtab, resolving all symbols
-   * (including enum default values) and finalizing the defs.  Only one def per
-   * name may be in the list, but defs can replace existing defs in the symtab.
-   * All defs must have a name -- anonymous defs are not allowed.  Anonymous
-   * defs can still be frozen by calling upb_def_freeze() directly.
-   *
-   * Any existing defs that can reach defs that are being replaced will
-   * themselves be replaced also, so that the resulting set of defs is fully
-   * consistent.
-   *
-   * This logic implemented in this method is a convenience; ultimately it
-   * calls some combination of upb_fielddef_setsubdef(), upb_def_dup(), and
-   * upb_freeze(), any of which the client could call themself.  However, since
-   * the logic for doing so is nontrivial, we provide it here.
-   *
-   * The entire operation either succeeds or fails.  If the operation fails,
-   * the symtab is unchanged, false is returned, and status indicates the
-   * error.  The caller passes a ref on all defs to the symtab (even if the
-   * operation fails).
-   *
-   * TODO(haberman): currently failure will leave the symtab unchanged, but may
-   * leave the defs themselves partially resolved.  Does this matter?  If so we
-   * could do a prepass that ensures that all symbols are resolvable and bail
-   * if not, so we don't mutate anything until we know the operation will
-   * succeed.
-   *
-   * TODO(haberman): since the defs must be mutable, refining a frozen def
-   * requires making mutable copies of the entire tree.  This is wasteful if
-   * only a few messages are changing.  We may want to add a way of adding a
-   * tree of frozen defs to the symtab (perhaps an alternate constructor where
-   * you pass the root of the tree?) */
-  bool Add(Def*const* defs, size_t n, void* ref_donor, Status* status);
+/* A union representing all possible protobuf values.  Used for generic get/set
+ * operations. */
 
-  bool Add(const std::vector<Def*>& defs, void *owner, Status* status) {
-    return Add((Def*const*)&defs[0], defs.size(), owner, status);
+typedef union {
+  bool b;
+  float flt;
+  double dbl;
+  int32_t i32;
+  int64_t i64;
+  uint32_t u32;
+  uint64_t u64;
+  const upb_map* map;
+  const upb_msg* msg;
+  const upb_array* arr;
+  const void* ptr;
+  struct {
+    const char *ptr;
+    size_t len;
+  } str;
+} upb_msgval;
+
+#define ACCESSORS(name, membername, ctype) \
+  UPB_INLINE ctype upb_msgval_get ## name(upb_msgval v) { \
+    return v.membername; \
+  } \
+  UPB_INLINE void upb_msgval_set ## name(upb_msgval *v, ctype cval) { \
+    v->membername = cval; \
+  } \
+  UPB_INLINE upb_msgval upb_msgval_ ## name(ctype v) { \
+    upb_msgval ret; \
+    ret.membername = v; \
+    return ret; \
   }
 
-  /* Resolves all subdefs for messages in this file and attempts to freeze the
-   * file.  If this succeeds, adds all the symbols to this SymbolTable
-   * (replacing any existing ones with the same names). */
-  bool AddFile(FileDef* file, Status* s);
+ACCESSORS(bool,   b,   bool)
+ACCESSORS(float,  flt, float)
+ACCESSORS(double, dbl, double)
+ACCESSORS(int32,  i32, int32_t)
+ACCESSORS(int64,  i64, int64_t)
+ACCESSORS(uint32, u32, uint32_t)
+ACCESSORS(uint64, u64, uint64_t)
+ACCESSORS(map,    map, const upb_map*)
+ACCESSORS(msg,    msg, const upb_msg*)
+ACCESSORS(ptr,    ptr, const void*)
+ACCESSORS(arr,    arr, const upb_array*)
+
+#undef ACCESSORS
+
+UPB_INLINE upb_msgval upb_msgval_str(const char *ptr, size_t len) {
+  upb_msgval ret;
+  ret.str.ptr = ptr;
+  ret.str.len = len;
+  return ret;
+}
 
- private:
-  UPB_DISALLOW_POD_OPS(SymbolTable, upb::SymbolTable)
-};
+UPB_INLINE const char* upb_msgval_getstr(upb_msgval val) {
+  return val.str.ptr;
+}
 
-#endif  /* __cplusplus */
+UPB_INLINE size_t upb_msgval_getstrlen(upb_msgval val) {
+  return val.str.len;
+}
 
-UPB_BEGIN_EXTERN_C
 
-/* Native C API. */
+/** upb_msg *******************************************************************/
 
-/* Include refcounted methods like upb_symtab_ref(). */
-UPB_REFCOUNTED_CMETHODS(upb_symtab, upb_symtab_upcast)
+/* A upb_msg represents a protobuf message.  It always corresponds to a specific
+ * upb_msglayout, which describes how it is laid out in memory.
+ *
+ * The message will have a fixed size, as returned by upb_msg_sizeof(), which
+ * will be used to store fixed-length fields.  The upb_msg may also allocate
+ * dynamic memory internally to store data such as:
+ *
+ * - extensions
+ * - unknown fields
+ */
 
-upb_symtab *upb_symtab_new(const void *owner);
-void upb_symtab_freeze(upb_symtab *s);
-const upb_def *upb_symtab_resolve(const upb_symtab *s, const char *base,
-                                  const char *sym);
-const upb_def *upb_symtab_lookup(const upb_symtab *s, const char *sym);
-const upb_msgdef *upb_symtab_lookupmsg(const upb_symtab *s, const char *sym);
-const upb_enumdef *upb_symtab_lookupenum(const upb_symtab *s, const char *sym);
-bool upb_symtab_add(upb_symtab *s, upb_def *const*defs, size_t n,
-                    void *ref_donor, upb_status *status);
-bool upb_symtab_addfile(upb_symtab *s, upb_filedef *file, upb_status* status);
+/* Returns the size of a message given this layout. */
+size_t upb_msg_sizeof(const upb_msglayout *l);
 
-/* upb_symtab_iter i;
- * for(upb_symtab_begin(&i, s, type); !upb_symtab_done(&i);
- *     upb_symtab_next(&i)) {
- *   const upb_def *def = upb_symtab_iter_def(&i);
- *    // ...
- * }
+/* upb_msg_init() / upb_msg_uninit() allow the user to use a pre-allocated
+ * block of memory as a message.  The block's size should be upb_msg_sizeof().
+ * upb_msg_uninit() must be called to release internally-allocated memory
+ * unless the allocator is an arena that does not require freeing.
  *
- * For C we don't have separate iterators for const and non-const.
- * It is the caller's responsibility to cast the upb_fielddef* to
- * const if the upb_msgdef* is const. */
-void upb_symtab_begin(upb_symtab_iter *iter, const upb_symtab *s,
-                      upb_deftype_t type);
-void upb_symtab_next(upb_symtab_iter *iter);
-bool upb_symtab_done(const upb_symtab_iter *iter);
-const upb_def *upb_symtab_iter_def(const upb_symtab_iter *iter);
+ * Please note that upb_msg_uninit() does *not* free any submessages, maps,
+ * or arrays referred to by this message's fields.  You must free them manually
+ * yourself. */
+void upb_msg_init(upb_msg *msg, const upb_msglayout *l, upb_alloc *a);
+void upb_msg_uninit(upb_msg *msg, const upb_msglayout *l);
+
+/* Like upb_msg_init() / upb_msg_uninit(), except the message's memory is
+ * allocated / freed from the given upb_alloc. */
+upb_msg *upb_msg_new(const upb_msglayout *l, upb_alloc *a);
+void upb_msg_free(upb_msg *msg, const upb_msglayout *l);
+
+/* Returns the upb_alloc for the given message. */
+upb_alloc *upb_msg_alloc(const upb_msg *msg, const upb_msglayout *l);
+
+/* Packs the tree of messages rooted at "msg" into a single hunk of memory,
+ * allocated from the given allocator. */
+void *upb_msg_pack(const upb_msg *msg, const upb_msglayout *l,
+                   void *p, size_t *ofs, size_t size);
+
+/* Read-only message API.  Can be safely called by anyone. */
+
+/* Returns the value associated with this field:
+ *   - for scalar fields (including strings), the value directly.
+ *   - return upb_msg*, or upb_map* for msg/map.
+ *     If the field is unset for these field types, returns NULL.
+ *
+ * TODO(haberman): should we let users store cached array/map/msg
+ * pointers here for fields that are unset?  Could be useful for the
+ * strongly-owned submessage model (ie. generated C API that doesn't use
+ * arenas).
+ */
+upb_msgval upb_msg_get(const upb_msg *msg,
+                       const upb_fielddef *f,
+                       const upb_msglayout *l);
 
-UPB_END_EXTERN_C
+/* May only be called for fields where upb_fielddef_haspresence(f) == true. */
+bool upb_msg_has(const upb_msg *msg,
+                 const upb_fielddef *f,
+                 const upb_msglayout *l);
 
-#ifdef __cplusplus
-/* C++ inline wrappers. */
-namespace upb {
-inline reffed_ptr<SymbolTable> SymbolTable::New() {
-  upb_symtab *s = upb_symtab_new(&s);
-  return reffed_ptr<SymbolTable>(s, &s);
-}
+/* Returns NULL if no field in the oneof is set. */
+const upb_fielddef *upb_msg_getoneofcase(const upb_msg *msg,
+                                         const upb_oneofdef *o,
+                                         const upb_msglayout *l);
 
-inline void SymbolTable::Freeze() {
-  return upb_symtab_freeze(this);
-}
-inline const Def *SymbolTable::Resolve(const char *base,
-                                       const char *sym) const {
-  return upb_symtab_resolve(this, base, sym);
-}
-inline const Def* SymbolTable::Lookup(const char *sym) const {
-  return upb_symtab_lookup(this, sym);
-}
-inline const MessageDef *SymbolTable::LookupMessage(const char *sym) const {
-  return upb_symtab_lookupmsg(this, sym);
-}
-inline bool SymbolTable::Add(
-    Def*const* defs, size_t n, void* ref_donor, Status* status) {
-  return upb_symtab_add(this, (upb_def*const*)defs, n, ref_donor, status);
-}
-inline bool SymbolTable::AddFile(FileDef* file, Status* s) {
-  return upb_symtab_addfile(this, file, s);
-}
-}  /* namespace upb */
-#endif
+/* Returns true if any field in the oneof is set. */
+bool upb_msg_hasoneof(const upb_msg *msg,
+                      const upb_oneofdef *o,
+                      const upb_msglayout *l);
+
+
+/* Mutable message API.  May only be called by the owner of the message who
+ * knows its ownership scheme and how to keep it consistent. */
+
+/* Sets the given field to the given value.  Does not perform any memory
+ * management: if you overwrite a pointer to a msg/array/map/string without
+ * cleaning it up (or using an arena) it will leak.
+ */
+bool upb_msg_set(upb_msg *msg,
+                 const upb_fielddef *f,
+                 upb_msgval val,
+                 const upb_msglayout *l);
+
+/* For a primitive field, set it back to its default. For repeated, string, and
+ * submessage fields set it back to NULL.  This could involve releasing some
+ * internal memory (for example, from an extension dictionary), but it is not
+ * recursive in any way and will not recover any memory that may be used by
+ * arrays/maps/strings/msgs that this field may have pointed to.
+ */
+bool upb_msg_clearfield(upb_msg *msg,
+                        const upb_fielddef *f,
+                        const upb_msglayout *l);
+
+/* Clears all fields in the oneof such that none of them are set. */
+bool upb_msg_clearoneof(upb_msg *msg,
+                        const upb_oneofdef *o,
+                        const upb_msglayout *l);
+
+/* TODO(haberman): copyfrom()/mergefrom()? */
+
+
+/** upb_array *****************************************************************/
+
+/* A upb_array stores data for a repeated field.  The memory management
+ * semantics are the same as upb_msg.  A upb_array allocates dynamic
+ * memory internally for the array elements. */
+
+size_t upb_array_sizeof(upb_fieldtype_t type);
+void upb_array_init(upb_array *arr, upb_fieldtype_t type, upb_alloc *a);
+void upb_array_uninit(upb_array *arr);
+upb_array *upb_array_new(upb_fieldtype_t type, upb_alloc *a);
+void upb_array_free(upb_array *arr);
+
+/* Read-only interface.  Safe for anyone to call. */
+
+size_t upb_array_size(const upb_array *arr);
+upb_fieldtype_t upb_array_type(const upb_array *arr);
+upb_msgval upb_array_get(const upb_array *arr, size_t i);
+
+/* Write interface.  May only be called by the message's owner who can enforce
+ * its memory management invariants. */
+
+bool upb_array_set(upb_array *arr, size_t i, upb_msgval val);
+
+
+/** upb_map *******************************************************************/
+
+/* A upb_map stores data for a map field.  The memory management semantics are
+ * the same as upb_msg, with one notable exception.  upb_map will internally
+ * store a copy of all string keys, but *not* any string values or submessages.
+ * So you must ensure that any string or message values outlive the map, and you
+ * must delete them manually when they are no longer required. */
+
+size_t upb_map_sizeof(upb_fieldtype_t ktype, upb_fieldtype_t vtype);
+bool upb_map_init(upb_map *map, upb_fieldtype_t ktype, upb_fieldtype_t vtype,
+                  upb_alloc *a);
+void upb_map_uninit(upb_map *map);
+upb_map *upb_map_new(upb_fieldtype_t ktype, upb_fieldtype_t vtype, upb_alloc *a);
+void upb_map_free(upb_map *map);
+
+/* Read-only interface.  Safe for anyone to call. */
+
+size_t upb_map_size(const upb_map *map);
+upb_fieldtype_t upb_map_keytype(const upb_map *map);
+upb_fieldtype_t upb_map_valuetype(const upb_map *map);
+bool upb_map_get(const upb_map *map, upb_msgval key, upb_msgval *val);
+
+/* Write interface.  May only be called by the message's owner who can enforce
+ * its memory management invariants. */
+
+/* Sets or overwrites an entry in the map.  Return value indicates whether
+ * the operation succeeded or failed with OOM, and also whether an existing
+ * key was replaced or not. */
+bool upb_map_set(upb_map *map,
+                 upb_msgval key, upb_msgval val,
+                 upb_msgval *valremoved);
+
+/* Deletes an entry in the map.  Returns true if the key was present. */
+bool upb_map_del(upb_map *map, upb_msgval key);
+
+
+/** upb_mapiter ***************************************************************/
+
+/* For iterating over a map.  Map iterators are invalidated by mutations to the
+ * map, but an invalidated iterator will never return junk or crash the process.
+ * An invalidated iterator may return entries that were already returned though,
+ * and if you keep invalidating the iterator during iteration, the program may
+ * enter an infinite loop. */
+
+size_t upb_mapiter_sizeof();
+
+void upb_mapiter_begin(upb_mapiter *i, const upb_map *t);
+upb_mapiter *upb_mapiter_new(const upb_map *t, upb_alloc *a);
+void upb_mapiter_free(upb_mapiter *i, upb_alloc *a);
+void upb_mapiter_next(upb_mapiter *i);
+bool upb_mapiter_done(const upb_mapiter *i);
+
+upb_msgval upb_mapiter_key(const upb_mapiter *i);
+upb_msgval upb_mapiter_value(const upb_mapiter *i);
+void upb_mapiter_setdone(upb_mapiter *i);
+bool upb_mapiter_isequal(const upb_mapiter *i1, const upb_mapiter *i2);
+
+
+/** Handlers ******************************************************************/
+
+/* These are the handlers used internally by upb_msgfactory_getmergehandlers().
+ * They write scalar data to a known offset from the message pointer.
+ *
+ * These would be trivial for anyone to implement themselves, but it's better
+ * to use these because some JITs will recognize and specialize these instead
+ * of actually calling the function. */
+
+/* Sets a handler for the given primitive field that will write the data at the
+ * given offset.  If hasbit > 0, also sets a hasbit at the given bit offset
+ * (addressing each byte low to high). */
+bool upb_msg_setscalarhandler(upb_handlers *h,
+                              const upb_fielddef *f,
+                              size_t offset,
+                              int32_t hasbit);
+
+/* If the given handler is a msghandlers_primitive field, returns true and sets
+ * *type, *offset and *hasbit.  Otherwise returns false. */
+bool upb_msg_getscalarhandlerdata(const upb_handlers *h,
+                                  upb_selector_t s,
+                                  upb_fieldtype_t *type,
+                                  size_t *offset,
+                                  int32_t *hasbit);
+
+UPB_END_EXTERN_C
 
-#endif  /* UPB_SYMTAB_H_ */
+#endif /* UPB_MSG_H_ */
 /*
 ** upb::descriptor::Reader (upb_descreader)
 **
@@ -6853,111 +7137,111 @@ UPB_INLINE bool upbdefs_google_protobuf_FileOptions_OptimizeMode_is(const upb_en
 
 
 /* Functions to get a fielddef from a msgdef reference. */
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_ExtensionRange_f_end(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_ExtensionRange_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_ExtensionRange_f_start(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_ExtensionRange_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_ReservedRange_f_end(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_ReservedRange_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_ReservedRange_f_start(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_ReservedRange_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_enum_type(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 4); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_extension(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 6); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_extension_range(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 5); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_field(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_nested_type(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_oneof_decl(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 8); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_options(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 7); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_reserved_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 10); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_reserved_range(const upb_msgdef *m) { assert(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 9); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumDescriptorProto_f_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumDescriptorProto_f_options(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumDescriptorProto_f_value(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumOptions_f_allow_alias(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumOptions_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumOptions_f_deprecated(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumOptions_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumOptions_f_uninterpreted_option(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumOptions_is(m)); return upb_msgdef_itof(m, 999); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueDescriptorProto_f_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumValueDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueDescriptorProto_f_number(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumValueDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueDescriptorProto_f_options(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumValueDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueOptions_f_deprecated(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumValueOptions_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueOptions_f_uninterpreted_option(const upb_msgdef *m) { assert(upbdefs_google_protobuf_EnumValueOptions_is(m)); return upb_msgdef_itof(m, 999); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_default_value(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 7); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_extendee(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_json_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 10); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_label(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 4); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_number(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_oneof_index(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 9); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_options(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 8); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_type(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 5); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_type_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 6); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_ctype(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_deprecated(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_jstype(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 6); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_lazy(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 5); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_packed(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_uninterpreted_option(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 999); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_weak(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 10); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_dependency(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_enum_type(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 5); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_extension(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 7); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_message_type(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 4); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_options(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 8); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_package(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_public_dependency(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 10); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_service(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 6); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_source_code_info(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 9); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_syntax(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 12); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_weak_dependency(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 11); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorSet_f_file(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileDescriptorSet_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_cc_enable_arenas(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 31); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_cc_generic_services(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 16); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_csharp_namespace(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 37); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_deprecated(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 23); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_go_package(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 11); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_generate_equals_and_hash(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 20); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_generic_services(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 17); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_multiple_files(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 10); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_outer_classname(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 8); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_package(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_string_check_utf8(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 27); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_javanano_use_deprecated_package(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 38); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_objc_class_prefix(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 36); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_optimize_for(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 9); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_py_generic_services(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 18); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_uninterpreted_option(const upb_msgdef *m) { assert(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 999); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_deprecated(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_map_entry(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 7); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_message_set_wire_format(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_no_standard_descriptor_accessor(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_uninterpreted_option(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 999); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_client_streaming(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 5); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_input_type(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_options(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 4); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_output_type(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_server_streaming(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 6); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodOptions_f_deprecated(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MethodOptions_is(m)); return upb_msgdef_itof(m, 33); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodOptions_f_uninterpreted_option(const upb_msgdef *m) { assert(upbdefs_google_protobuf_MethodOptions_is(m)); return upb_msgdef_itof(m, 999); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_OneofDescriptorProto_f_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_OneofDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceDescriptorProto_f_method(const upb_msgdef *m) { assert(upbdefs_google_protobuf_ServiceDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceDescriptorProto_f_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_ServiceDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceDescriptorProto_f_options(const upb_msgdef *m) { assert(upbdefs_google_protobuf_ServiceDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceOptions_f_deprecated(const upb_msgdef *m) { assert(upbdefs_google_protobuf_ServiceOptions_is(m)); return upb_msgdef_itof(m, 33); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceOptions_f_uninterpreted_option(const upb_msgdef *m) { assert(upbdefs_google_protobuf_ServiceOptions_is(m)); return upb_msgdef_itof(m, 999); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_leading_comments(const upb_msgdef *m) { assert(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_leading_detached_comments(const upb_msgdef *m) { assert(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 6); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_path(const upb_msgdef *m) { assert(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_span(const upb_msgdef *m) { assert(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_trailing_comments(const upb_msgdef *m) { assert(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 4); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_f_location(const upb_msgdef *m) { assert(upbdefs_google_protobuf_SourceCodeInfo_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_NamePart_f_is_extension(const upb_msgdef *m) { assert(upbdefs_google_protobuf_UninterpretedOption_NamePart_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_NamePart_f_name_part(const upb_msgdef *m) { assert(upbdefs_google_protobuf_UninterpretedOption_NamePart_is(m)); return upb_msgdef_itof(m, 1); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_aggregate_value(const upb_msgdef *m) { assert(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 8); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_double_value(const upb_msgdef *m) { assert(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 6); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_identifier_value(const upb_msgdef *m) { assert(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 3); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_name(const upb_msgdef *m) { assert(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 2); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_negative_int_value(const upb_msgdef *m) { assert(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 5); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_positive_int_value(const upb_msgdef *m) { assert(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 4); }
-UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_string_value(const upb_msgdef *m) { assert(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 7); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_ExtensionRange_f_end(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_ExtensionRange_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_ExtensionRange_f_start(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_ExtensionRange_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_ReservedRange_f_end(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_ReservedRange_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_ReservedRange_f_start(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_ReservedRange_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_enum_type(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 4); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_extension(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 6); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_extension_range(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 5); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_field(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_nested_type(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_oneof_decl(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 8); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_options(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 7); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_reserved_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 10); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_DescriptorProto_f_reserved_range(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m)); return upb_msgdef_itof(m, 9); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumDescriptorProto_f_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumDescriptorProto_f_options(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumDescriptorProto_f_value(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumOptions_f_allow_alias(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumOptions_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumOptions_f_deprecated(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumOptions_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumOptions_f_uninterpreted_option(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumOptions_is(m)); return upb_msgdef_itof(m, 999); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueDescriptorProto_f_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumValueDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueDescriptorProto_f_number(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumValueDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueDescriptorProto_f_options(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumValueDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueOptions_f_deprecated(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumValueOptions_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_EnumValueOptions_f_uninterpreted_option(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_EnumValueOptions_is(m)); return upb_msgdef_itof(m, 999); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_default_value(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 7); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_extendee(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_json_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 10); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_label(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 4); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_number(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_oneof_index(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 9); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_options(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 8); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_type(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 5); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldDescriptorProto_f_type_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m)); return upb_msgdef_itof(m, 6); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_ctype(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_deprecated(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_jstype(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 6); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_lazy(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 5); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_packed(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_uninterpreted_option(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 999); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FieldOptions_f_weak(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_is(m)); return upb_msgdef_itof(m, 10); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_dependency(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_enum_type(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 5); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_extension(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 7); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_message_type(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 4); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_options(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 8); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_package(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_public_dependency(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 10); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_service(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 6); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_source_code_info(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 9); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_syntax(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 12); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorProto_f_weak_dependency(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m)); return upb_msgdef_itof(m, 11); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileDescriptorSet_f_file(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorSet_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_cc_enable_arenas(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 31); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_cc_generic_services(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 16); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_csharp_namespace(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 37); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_deprecated(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 23); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_go_package(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 11); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_generate_equals_and_hash(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 20); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_generic_services(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 17); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_multiple_files(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 10); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_outer_classname(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 8); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_package(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_java_string_check_utf8(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 27); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_javanano_use_deprecated_package(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 38); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_objc_class_prefix(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 36); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_optimize_for(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 9); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_py_generic_services(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 18); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_FileOptions_f_uninterpreted_option(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m)); return upb_msgdef_itof(m, 999); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_deprecated(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_map_entry(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 7); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_message_set_wire_format(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_no_standard_descriptor_accessor(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MessageOptions_f_uninterpreted_option(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MessageOptions_is(m)); return upb_msgdef_itof(m, 999); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_client_streaming(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 5); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_input_type(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_options(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 4); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_output_type(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodDescriptorProto_f_server_streaming(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MethodDescriptorProto_is(m)); return upb_msgdef_itof(m, 6); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodOptions_f_deprecated(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MethodOptions_is(m)); return upb_msgdef_itof(m, 33); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_MethodOptions_f_uninterpreted_option(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_MethodOptions_is(m)); return upb_msgdef_itof(m, 999); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_OneofDescriptorProto_f_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_OneofDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceDescriptorProto_f_method(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_ServiceDescriptorProto_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceDescriptorProto_f_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_ServiceDescriptorProto_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceDescriptorProto_f_options(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_ServiceDescriptorProto_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceOptions_f_deprecated(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_ServiceOptions_is(m)); return upb_msgdef_itof(m, 33); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_ServiceOptions_f_uninterpreted_option(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_ServiceOptions_is(m)); return upb_msgdef_itof(m, 999); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_leading_comments(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_leading_detached_comments(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 6); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_path(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_span(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_Location_f_trailing_comments(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m)); return upb_msgdef_itof(m, 4); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_SourceCodeInfo_f_location(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_SourceCodeInfo_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_NamePart_f_is_extension(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_NamePart_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_NamePart_f_name_part(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_NamePart_is(m)); return upb_msgdef_itof(m, 1); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_aggregate_value(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 8); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_double_value(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 6); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_identifier_value(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 3); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_name(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 2); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_negative_int_value(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 5); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_positive_int_value(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 4); }
+UPB_INLINE const upb_fielddef *upbdefs_google_protobuf_UninterpretedOption_f_string_value(const upb_msgdef *m) { UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_is(m)); return upb_msgdef_itof(m, 7); }
 
 UPB_END_EXTERN_C
 
@@ -6971,7 +7255,7 @@ class DescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   DescriptorProto(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_DescriptorProto_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_is(m));
   }
 
   static DescriptorProto get() {
@@ -6983,7 +7267,7 @@ class DescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef> {
    public:
     ExtensionRange(const ::upb::MessageDef* m, const void *ref_donor = NULL)
         : reffed_ptr(m, ref_donor) {
-      assert(upbdefs_google_protobuf_DescriptorProto_ExtensionRange_is(m));
+      UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_ExtensionRange_is(m));
     }
 
     static ExtensionRange get() {
@@ -6996,7 +7280,7 @@ class DescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef> {
    public:
     ReservedRange(const ::upb::MessageDef* m, const void *ref_donor = NULL)
         : reffed_ptr(m, ref_donor) {
-      assert(upbdefs_google_protobuf_DescriptorProto_ReservedRange_is(m));
+      UPB_ASSERT(upbdefs_google_protobuf_DescriptorProto_ReservedRange_is(m));
     }
 
     static ReservedRange get() {
@@ -7010,7 +7294,7 @@ class EnumDescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   EnumDescriptorProto(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_EnumDescriptorProto_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_EnumDescriptorProto_is(m));
   }
 
   static EnumDescriptorProto get() {
@@ -7023,7 +7307,7 @@ class EnumOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   EnumOptions(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_EnumOptions_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_EnumOptions_is(m));
   }
 
   static EnumOptions get() {
@@ -7036,7 +7320,7 @@ class EnumValueDescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDe
  public:
   EnumValueDescriptorProto(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_EnumValueDescriptorProto_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_EnumValueDescriptorProto_is(m));
   }
 
   static EnumValueDescriptorProto get() {
@@ -7049,7 +7333,7 @@ class EnumValueOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   EnumValueOptions(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_EnumValueOptions_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_EnumValueOptions_is(m));
   }
 
   static EnumValueOptions get() {
@@ -7062,7 +7346,7 @@ class FieldDescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   FieldDescriptorProto(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_FieldDescriptorProto_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_is(m));
   }
 
   static FieldDescriptorProto get() {
@@ -7074,7 +7358,7 @@ class FieldDescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef> {
    public:
     Label(const ::upb::EnumDef* e, const void *ref_donor = NULL)
         : reffed_ptr(e, ref_donor) {
-      assert(upbdefs_google_protobuf_FieldDescriptorProto_Label_is(e));
+      UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_Label_is(e));
     }
     static Label get() {
       const ::upb::EnumDef* e = upbdefs_google_protobuf_FieldDescriptorProto_Label_get(&e);
@@ -7086,7 +7370,7 @@ class FieldDescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef> {
    public:
     Type(const ::upb::EnumDef* e, const void *ref_donor = NULL)
         : reffed_ptr(e, ref_donor) {
-      assert(upbdefs_google_protobuf_FieldDescriptorProto_Type_is(e));
+      UPB_ASSERT(upbdefs_google_protobuf_FieldDescriptorProto_Type_is(e));
     }
     static Type get() {
       const ::upb::EnumDef* e = upbdefs_google_protobuf_FieldDescriptorProto_Type_get(&e);
@@ -7099,7 +7383,7 @@ class FieldOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   FieldOptions(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_FieldOptions_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_is(m));
   }
 
   static FieldOptions get() {
@@ -7111,7 +7395,7 @@ class FieldOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
    public:
     CType(const ::upb::EnumDef* e, const void *ref_donor = NULL)
         : reffed_ptr(e, ref_donor) {
-      assert(upbdefs_google_protobuf_FieldOptions_CType_is(e));
+      UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_CType_is(e));
     }
     static CType get() {
       const ::upb::EnumDef* e = upbdefs_google_protobuf_FieldOptions_CType_get(&e);
@@ -7123,7 +7407,7 @@ class FieldOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
    public:
     JSType(const ::upb::EnumDef* e, const void *ref_donor = NULL)
         : reffed_ptr(e, ref_donor) {
-      assert(upbdefs_google_protobuf_FieldOptions_JSType_is(e));
+      UPB_ASSERT(upbdefs_google_protobuf_FieldOptions_JSType_is(e));
     }
     static JSType get() {
       const ::upb::EnumDef* e = upbdefs_google_protobuf_FieldOptions_JSType_get(&e);
@@ -7136,7 +7420,7 @@ class FileDescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   FileDescriptorProto(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_FileDescriptorProto_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorProto_is(m));
   }
 
   static FileDescriptorProto get() {
@@ -7149,7 +7433,7 @@ class FileDescriptorSet : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   FileDescriptorSet(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_FileDescriptorSet_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_FileDescriptorSet_is(m));
   }
 
   static FileDescriptorSet get() {
@@ -7162,7 +7446,7 @@ class FileOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   FileOptions(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_FileOptions_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_FileOptions_is(m));
   }
 
   static FileOptions get() {
@@ -7174,7 +7458,7 @@ class FileOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
    public:
     OptimizeMode(const ::upb::EnumDef* e, const void *ref_donor = NULL)
         : reffed_ptr(e, ref_donor) {
-      assert(upbdefs_google_protobuf_FileOptions_OptimizeMode_is(e));
+      UPB_ASSERT(upbdefs_google_protobuf_FileOptions_OptimizeMode_is(e));
     }
     static OptimizeMode get() {
       const ::upb::EnumDef* e = upbdefs_google_protobuf_FileOptions_OptimizeMode_get(&e);
@@ -7187,7 +7471,7 @@ class MessageOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   MessageOptions(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_MessageOptions_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_MessageOptions_is(m));
   }
 
   static MessageOptions get() {
@@ -7200,7 +7484,7 @@ class MethodDescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef>
  public:
   MethodDescriptorProto(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_MethodDescriptorProto_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_MethodDescriptorProto_is(m));
   }
 
   static MethodDescriptorProto get() {
@@ -7213,7 +7497,7 @@ class MethodOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   MethodOptions(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_MethodOptions_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_MethodOptions_is(m));
   }
 
   static MethodOptions get() {
@@ -7226,7 +7510,7 @@ class OneofDescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   OneofDescriptorProto(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_OneofDescriptorProto_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_OneofDescriptorProto_is(m));
   }
 
   static OneofDescriptorProto get() {
@@ -7239,7 +7523,7 @@ class ServiceDescriptorProto : public ::upb::reffed_ptr<const ::upb::MessageDef>
  public:
   ServiceDescriptorProto(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_ServiceDescriptorProto_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_ServiceDescriptorProto_is(m));
   }
 
   static ServiceDescriptorProto get() {
@@ -7252,7 +7536,7 @@ class ServiceOptions : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   ServiceOptions(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_ServiceOptions_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_ServiceOptions_is(m));
   }
 
   static ServiceOptions get() {
@@ -7265,7 +7549,7 @@ class SourceCodeInfo : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   SourceCodeInfo(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_SourceCodeInfo_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_SourceCodeInfo_is(m));
   }
 
   static SourceCodeInfo get() {
@@ -7277,7 +7561,7 @@ class SourceCodeInfo : public ::upb::reffed_ptr<const ::upb::MessageDef> {
    public:
     Location(const ::upb::MessageDef* m, const void *ref_donor = NULL)
         : reffed_ptr(m, ref_donor) {
-      assert(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m));
+      UPB_ASSERT(upbdefs_google_protobuf_SourceCodeInfo_Location_is(m));
     }
 
     static Location get() {
@@ -7291,7 +7575,7 @@ class UninterpretedOption : public ::upb::reffed_ptr<const ::upb::MessageDef> {
  public:
   UninterpretedOption(const ::upb::MessageDef* m, const void *ref_donor = NULL)
       : reffed_ptr(m, ref_donor) {
-    assert(upbdefs_google_protobuf_UninterpretedOption_is(m));
+    UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_is(m));
   }
 
   static UninterpretedOption get() {
@@ -7303,7 +7587,7 @@ class UninterpretedOption : public ::upb::reffed_ptr<const ::upb::MessageDef> {
    public:
     NamePart(const ::upb::MessageDef* m, const void *ref_donor = NULL)
         : reffed_ptr(m, ref_donor) {
-      assert(upbdefs_google_protobuf_UninterpretedOption_NamePart_is(m));
+      UPB_ASSERT(upbdefs_google_protobuf_UninterpretedOption_NamePart_is(m));
     }
 
     static NamePart get() {
@@ -8112,9 +8396,9 @@ UPB_INLINE uint64_t upb_vencode32(uint32_t val) {
   char buf[UPB_PB_VARINT_MAX_LEN];
   size_t bytes = upb_vencode64(val, buf);
   uint64_t ret = 0;
-  assert(bytes <= 5);
+  UPB_ASSERT(bytes <= 5);
   memcpy(&ret, buf, bytes);
-  assert(ret <= 0xffffffffffU);
+  UPB_ASSERT(ret <= 0xffffffffffU);
   return ret;
 }