Fix ruby segment fault (#3708)

* Fix ruby segment fault

1) rb_ary_new cannot be called during allocate function. During allocate
fucntion, the containing object hasn't been marked and rb_ary_new may
invoke gc to collect containing object.
2) The global map should be marked before allocating it. Otherwise it
may be garbage collected.

* Add test

* Remove commented code

* Fix grammer error

3 files changed, 16 insertions, 8 deletions

diff --git a/ruby/ext/google/protobuf_c/defs.c b/ruby/ext/google/protobuf_c/defs.c
index 845c0225..34d9663a 100644
--- a/ruby/ext/google/protobuf_c/defs.c
+++ b/ruby/ext/google/protobuf_c/defs.c
@@ -228,7 +228,6 @@ DEFINE_CLASS(Descriptor, "Google::Protobuf::Descriptor");
 void Descriptor_mark(void* _self) {
   Descriptor* self = _self;
   rb_gc_mark(self->klass);
-  rb_gc_mark(self->typeclass_references);
 }
 
 void Descriptor_free(void* _self) {
@@ -283,7 +282,6 @@ VALUE Descriptor_alloc(VALUE klass) {
   self->pb_serialize_handlers = NULL;
   self->json_serialize_handlers = NULL;
   self->json_serialize_handlers_preserve = NULL;
-  self->typeclass_references = rb_ary_new();
   return ret;
 }
 
@@ -1635,7 +1633,7 @@ VALUE Builder_alloc(VALUE klass) {
   Builder* self = ALLOC(Builder);
   VALUE ret = TypedData_Wrap_Struct(
       klass, &_Builder_type, self);
-  self->pending_list = rb_ary_new();
+  self->pending_list = Qnil;
   self->defs = NULL;
   return ret;
 }
@@ -1645,6 +1643,7 @@ void Builder_register(VALUE module) {
   rb_define_alloc_func(klass, Builder_alloc);
   rb_define_method(klass, "add_message", Builder_add_message, 1);
   rb_define_method(klass, "add_enum", Builder_add_enum, 1);
+  rb_define_method(klass, "initialize", Builder_initialize, 0);
   rb_define_method(klass, "finalize_to_pool", Builder_finalize_to_pool, 1);
   cBuilder = klass;
   rb_gc_register_address(&cBuilder);
@@ -1652,6 +1651,18 @@ void Builder_register(VALUE module) {
 
 /*
  * call-seq:
+ *     Builder.new(d) => builder
+ *
+ * Create a new message builder.
+ */
+VALUE Builder_initialize(VALUE _self) {
+  DEFINE_SELF(Builder, self, _self);
+  self->pending_list = rb_ary_new();
+  return Qnil;
+}
+
+/*
+ * call-seq:
  *     Builder.add_message(name, &block)
  *
  * Creates a new, empty descriptor with the given name, and invokes the block in
diff --git a/ruby/ext/google/protobuf_c/protobuf.c b/ruby/ext/google/protobuf_c/protobuf.c
index 7cde4aec..c7750c44 100644
--- a/ruby/ext/google/protobuf_c/protobuf.c
+++ b/ruby/ext/google/protobuf_c/protobuf.c
@@ -110,6 +110,6 @@ void Init_protobuf_c() {
   kRubyStringASCIIEncoding = rb_usascii_encoding();
   kRubyString8bitEncoding = rb_ascii8bit_encoding();
 
-  upb_def_to_ruby_obj_map = rb_hash_new();
   rb_gc_register_address(&upb_def_to_ruby_obj_map);
+  upb_def_to_ruby_obj_map = rb_hash_new();
 }
diff --git a/ruby/ext/google/protobuf_c/protobuf.h b/ruby/ext/google/protobuf_c/protobuf.h
index f4b110fe..21c7f001 100644
--- a/ruby/ext/google/protobuf_c/protobuf.h
+++ b/ruby/ext/google/protobuf_c/protobuf.h
@@ -116,10 +116,6 @@ struct Descriptor {
   const upb_handlers* pb_serialize_handlers;
   const upb_handlers* json_serialize_handlers;
   const upb_handlers* json_serialize_handlers_preserve;
-  // Handlers hold type class references for sub-message fields directly in some
-  // cases. We need to keep these rooted because they might otherwise be
-  // collected.
-  VALUE typeclass_references;
 };
 
 struct FieldDescriptor {
@@ -280,6 +276,7 @@ void Builder_free(void* _self);
 VALUE Builder_alloc(VALUE klass);
 void Builder_register(VALUE module);
 Builder* ruby_to_Builder(VALUE value);
+VALUE Builder_initialize(VALUE _self);
 VALUE Builder_add_message(VALUE _self, VALUE name);
 VALUE Builder_add_enum(VALUE _self, VALUE name);
 VALUE Builder_finalize_to_pool(VALUE _self, VALUE pool_rb);