Export of internal Abseil changes

--
69b5d0b2a5adb49a53e51f9da6848eaa484242fe by Derek Mauro <dmauro@google.com>:

Changes the absl::Duration factory functions to disallow types that
are convertible to int or double, instead requiring that the argument
itself is indeed an integer or a floating-point number. This will
prevent callers from passing arguments, such as std::atomic<T>.

This change is an API break. Information and a tool to fix issues
can be found at
https://abseil.io/docs/cpp/tools/upgrades/duration-conversions

PiperOrigin-RevId: 387153494

--
786063e438ab6a55ac4baa88ad4d20a8293be52a by Evan Brown <ezb@google.com>:

Make ctrl_t be an enum class.

This adds type safety, and also when strict aliasing is enabled, the compiler will know that control bytes can't alias non-control bytes.

Also make H2() return h2_t.

PiperOrigin-RevId: 387120717

--
7e537aabec1c255d6e7c9d21232c597c1c2077bf by Evan Brown <ezb@google.com>:

Add some missing `const` keywords to ctrl_t* function parameters.

PiperOrigin-RevId: 386976062

--
da53ac6d91cabd951e81dd0a145e1e52b918955f by Martijn Vels <mvels@google.com>:

Change Seek and InitOffset to return nullptr instead of assert / fail.

This makes it consistent with the rest of the API (Next, Previous, Skip) and hardens it against invariants that are harder (or less likey) to be upheld correctly by the caller.

PiperOrigin-RevId: 386963283

--
a4d1faac020d5025edf53ce81808e5db68da7d89 by Abseil Team <absl-team@google.com>:

PC / Backtrace / Symbolization for Emscripten.

PiperOrigin-RevId: 386957724

--
97f2c47d83ba9d3ac89e1f55bd06897686ffd063 by Martijn Vels <mvels@google.com>:

Fix static casts ([-Wimplicit-int-conversion])

PiperOrigin-RevId: 386951646

--
9530c795248543817cbc4013953baa09c35f5e1a by Abseil Team <absl-team@google.com>:

Fix incorrect header guard in cord_rep_btree_navigator.h

PiperOrigin-RevId: 386907904

--
90ce5872406df2b7f4c428683741dc13a572267e by Abseil Team <absl-team@google.com>:

Small grammar fixes for some StatusCode descriptions.

PiperOrigin-RevId: 386906217

--
b30a2fd777f12a04a4d512f37a34614b0d05ce99 by Derek Mauro <dmauro@google.com>:

Skip length checking when constructing absl::string_view from std::string.
The length check causes unnecessary code bloat.

PiperOrigin-RevId: 386857974

--
fa171536c359bfa2a1b80297e844519bb9ee7791 by Martijn Vels <mvels@google.com>:

Introduce CordRepBtreeNavigator

CordRepBtreeNavigator implements bi-directional navigation over all data edges stored inside a Cord Btree.

PiperOrigin-RevId: 386519102
GitOrigin-RevId: 69b5d0b2a5adb49a53e51f9da6848eaa484242fe
Change-Id: I1b35188d66133f8cb73d346bc5564aac4e0b3e80

9 files changed, 216 insertions, 15 deletions

diff --git a/absl/debugging/BUILD.bazel b/absl/debugging/BUILD.bazel
index 2aac0f66..a8c51a5c 100644
--- a/absl/debugging/BUILD.bazel
+++ b/absl/debugging/BUILD.bazel
@@ -34,6 +34,7 @@ cc_library(
         "internal/stacktrace_aarch64-inl.inc",
         "internal/stacktrace_arm-inl.inc",
         "internal/stacktrace_config.h",
+        "internal/stacktrace_emscripten-inl.inc",
         "internal/stacktrace_generic-inl.inc",
         "internal/stacktrace_powerpc-inl.inc",
         "internal/stacktrace_unimplemented-inl.inc",
@@ -57,6 +58,7 @@ cc_library(
         "symbolize.cc",
         "symbolize_darwin.inc",
         "symbolize_elf.inc",
+        "symbolize_emscripten.inc",
         "symbolize_unimplemented.inc",
         "symbolize_win32.inc",
     ],
diff --git a/absl/debugging/CMakeLists.txt b/absl/debugging/CMakeLists.txt
index bb4d4c92..760772f3 100644
--- a/absl/debugging/CMakeLists.txt
+++ b/absl/debugging/CMakeLists.txt
@@ -22,6 +22,7 @@ absl_cc_library(
     "internal/stacktrace_aarch64-inl.inc"
     "internal/stacktrace_arm-inl.inc"
     "internal/stacktrace_config.h"
+    "internal/stacktrace_emscripten-inl.inc"
     "internal/stacktrace_generic-inl.inc"
     "internal/stacktrace_powerpc-inl.inc"
     "internal/stacktrace_unimplemented-inl.inc"
@@ -48,6 +49,7 @@ absl_cc_library(
     "symbolize.cc"
     "symbolize_darwin.inc"
     "symbolize_elf.inc"
+    "symbolize_emscripten.inc"
     "symbolize_unimplemented.inc"
     "symbolize_win32.inc"
   COPTS
diff --git a/absl/debugging/internal/stacktrace_config.h b/absl/debugging/internal/stacktrace_config.h
index cca410d4..6cceef26 100644
--- a/absl/debugging/internal/stacktrace_config.h
+++ b/absl/debugging/internal/stacktrace_config.h
@@ -37,6 +37,10 @@
   "absl/debugging/internal/stacktrace_generic-inl.inc"
 #endif
 
+#elif defined(__EMSCRIPTEN__)
+#define ABSL_STACKTRACE_INL_HEADER \
+  "absl/debugging/internal/stacktrace_emscripten-inl.inc"
+
 #elif defined(__linux__) && !defined(__ANDROID__)
 
 #if defined(NO_FRAME_POINTER) && \
@@ -68,7 +72,6 @@
   "absl/debugging/internal/stacktrace_generic-inl.inc"
 #endif
 #endif
-
 #endif
 
 // Fallback to the empty implementation.
diff --git a/absl/debugging/internal/stacktrace_emscripten-inl.inc b/absl/debugging/internal/stacktrace_emscripten-inl.inc
new file mode 100644
index 00000000..0f444514
--- /dev/null
+++ b/absl/debugging/internal/stacktrace_emscripten-inl.inc
@@ -0,0 +1,110 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Portable implementation - just use glibc
+//
+// Note:  The glibc implementation may cause a call to malloc.
+// This can cause a deadlock in HeapProfiler.
+
+#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_EMSCRIPTEN_INL_H_
+#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_EMSCRIPTEN_INL_H_
+
+#include <emscripten.h>
+
+#include <atomic>
+#include <cstring>
+
+#include "absl/base/attributes.h"
+#include "absl/debugging/stacktrace.h"
+
+extern "C" {
+uintptr_t emscripten_stack_snapshot();
+uint32_t emscripten_stack_unwind_buffer(uintptr_t pc, void *buffer,
+                                        uint32_t depth);
+}
+
+// Sometimes, we can try to get a stack trace from within a stack
+// trace, which can cause a self-deadlock.
+// Protect against such reentrant call by failing to get a stack trace.
+//
+// We use __thread here because the code here is extremely low level -- it is
+// called while collecting stack traces from within malloc and mmap, and thus
+// can not call anything which might call malloc or mmap itself.
+static __thread int recursive = 0;
+
+// The stack trace function might be invoked very early in the program's
+// execution (e.g. from the very first malloc).
+// As such, we suppress usage of backtrace during this early stage of execution.
+static std::atomic<bool> disable_stacktraces(true);  // Disabled until healthy.
+// Waiting until static initializers run seems to be late enough.
+// This file is included into stacktrace.cc so this will only run once.
+ABSL_ATTRIBUTE_UNUSED static int stacktraces_enabler = []() {
+  // Check if we can even create stacktraces. If not, bail early and leave
+  // disable_stacktraces set as-is.
+  // clang-format off
+  if (!EM_ASM_INT({ return (typeof wasmOffsetConverter !== 'undefined'); })) {
+    return 0;
+  }
+  // clang-format on
+  disable_stacktraces.store(false, std::memory_order_relaxed);
+  return 0;
+}();
+
+template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
+static int UnwindImpl(void **result, int *sizes, int max_depth, int skip_count,
+                      const void *ucp, int *min_dropped_frames) {
+  if (recursive || disable_stacktraces.load(std::memory_order_relaxed)) {
+    return 0;
+  }
+  ++recursive;
+
+  static_cast<void>(ucp);  // Unused.
+  constexpr int kStackLength = 64;
+  void *stack[kStackLength];
+
+  int size;
+  uintptr_t pc = emscripten_stack_snapshot();
+  size = emscripten_stack_unwind_buffer(pc, stack, kStackLength);
+
+  int result_count = size - skip_count;
+  if (result_count < 0) result_count = 0;
+  if (result_count > max_depth) result_count = max_depth;
+  for (int i = 0; i < result_count; i++) result[i] = stack[i + skip_count];
+
+  if (IS_STACK_FRAMES) {
+    // No implementation for finding out the stack frame sizes yet.
+    memset(sizes, 0, sizeof(*sizes) * result_count);
+  }
+  if (min_dropped_frames != nullptr) {
+    if (size - skip_count - max_depth > 0) {
+      *min_dropped_frames = size - skip_count - max_depth;
+    } else {
+      *min_dropped_frames = 0;
+    }
+  }
+
+  --recursive;
+
+  return result_count;
+}
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace debugging_internal {
+bool StackTraceWorksForTest() { return true; }
+}  // namespace debugging_internal
+ABSL_NAMESPACE_END
+}  // namespace absl
+
+#endif  // ABSL_DEBUGGING_INTERNAL_STACKTRACE_EMSCRIPTEN_INL_H_
diff --git a/absl/debugging/internal/symbolize.h b/absl/debugging/internal/symbolize.h
index 4f26130f..8c296f89 100644
--- a/absl/debugging/internal/symbolize.h
+++ b/absl/debugging/internal/symbolize.h
@@ -68,6 +68,12 @@ ABSL_NAMESPACE_END
 #define ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE 1
 #endif
 
+#ifdef ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE
+#error ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE cannot be directly set
+#elif defined(__EMSCRIPTEN__)
+#define ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE 1
+#endif
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 namespace debugging_internal {
diff --git a/absl/debugging/stacktrace.cc b/absl/debugging/stacktrace.cc
index 1f7c7d82..5358b942 100644
--- a/absl/debugging/stacktrace.cc
+++ b/absl/debugging/stacktrace.cc
@@ -49,6 +49,7 @@
 
 # include "absl/debugging/internal/stacktrace_aarch64-inl.inc"
 # include "absl/debugging/internal/stacktrace_arm-inl.inc"
+# include "absl/debugging/internal/stacktrace_emscripten-inl.inc"
 # include "absl/debugging/internal/stacktrace_generic-inl.inc"
 # include "absl/debugging/internal/stacktrace_powerpc-inl.inc"
 # include "absl/debugging/internal/stacktrace_unimplemented-inl.inc"
diff --git a/absl/debugging/symbolize.cc b/absl/debugging/symbolize.cc
index 5e4a25d6..f1abdfda 100644
--- a/absl/debugging/symbolize.cc
+++ b/absl/debugging/symbolize.cc
@@ -31,6 +31,8 @@
 #include "absl/debugging/symbolize_win32.inc"
 #elif defined(__APPLE__)
 #include "absl/debugging/symbolize_darwin.inc"
+#elif defined(__EMSCRIPTEN__)
+#include "absl/debugging/symbolize_emscripten.inc"
 #else
 #include "absl/debugging/symbolize_unimplemented.inc"
 #endif
diff --git a/absl/debugging/symbolize_emscripten.inc b/absl/debugging/symbolize_emscripten.inc
new file mode 100644
index 00000000..c226c456
--- /dev/null
+++ b/absl/debugging/symbolize_emscripten.inc
@@ -0,0 +1,72 @@
+// Copyright 2020 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <cxxabi.h>
+#include <emscripten.h>
+
+#include <algorithm>
+#include <cstring>
+
+#include "absl/base/internal/raw_logging.h"
+#include "absl/debugging/internal/demangle.h"
+#include "absl/strings/numbers.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+
+extern "C" {
+const char* emscripten_pc_get_function(const void* pc);
+}
+
+// clang-format off
+EM_JS(bool, HaveOffsetConverter, (),
+      { return typeof wasmOffsetConverter !== 'undefined'; });
+// clang-format on
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+void InitializeSymbolizer(const char*) {
+  if (!HaveOffsetConverter()) {
+    ABSL_RAW_LOG(INFO,
+                 "Symbolization unavailable. Rebuild with -sWASM=1 "
+                 "and -sUSE_OFFSET_CONVERTER=1.");
+  }
+}
+
+bool Symbolize(const void* pc, char* out, int out_size) {
+  // Check if we have the offset converter necessary for pc_get_function.
+  // Without it, the program will abort().
+  if (!HaveOffsetConverter()) {
+    return false;
+  }
+  const char* func_name = emscripten_pc_get_function(pc);
+  if (func_name == nullptr) {
+    return false;
+  }
+
+  strncpy(out, func_name, out_size);
+
+  if (out[out_size - 1] != '\0') {
+    // strncpy() does not '\0' terminate when it truncates.
+    static constexpr char kEllipsis[] = "...";
+    int ellipsis_size = std::min<int>(sizeof(kEllipsis) - 1, out_size - 1);
+    memcpy(out + out_size - ellipsis_size - 1, kEllipsis, ellipsis_size);
+    out[out_size - 1] = '\0';
+  }
+
+  return true;
+}
+
+ABSL_NAMESPACE_END
+}  // namespace absl
diff --git a/absl/debugging/symbolize_test.cc b/absl/debugging/symbolize_test.cc
index 35de02e2..c710a3da 100644
--- a/absl/debugging/symbolize_test.cc
+++ b/absl/debugging/symbolize_test.cc
@@ -146,8 +146,22 @@ static const char *TrySymbolize(void *pc) {
   return TrySymbolizeWithLimit(pc, sizeof(try_symbolize_buffer));
 }
 
-#if defined(ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE) || \
-    defined(ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE)
+#if defined(ABSL_INTERNAL_HAVE_ELF_SYMBOLIZE) ||    \
+    defined(ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE) || \
+    defined(ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE)
+
+// Test with a return address.
+void ABSL_ATTRIBUTE_NOINLINE TestWithReturnAddress() {
+#if defined(ABSL_HAVE_ATTRIBUTE_NOINLINE)
+  void *return_address = __builtin_return_address(0);
+  const char *symbol = TrySymbolize(return_address);
+  ABSL_RAW_CHECK(symbol != nullptr, "TestWithReturnAddress failed");
+  ABSL_RAW_CHECK(strcmp(symbol, "main") == 0, "TestWithReturnAddress failed");
+  std::cout << "TestWithReturnAddress passed" << std::endl;
+#endif
+}
+
+#ifndef ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE
 
 TEST(Symbolize, Cached) {
   // Compilers should give us pointers to them.
@@ -418,6 +432,7 @@ TEST(Symbolize, ForEachSection) {
   close(fd);
 }
 #endif  // !ABSL_INTERNAL_HAVE_DARWIN_SYMBOLIZE
+#endif  // !ABSL_INTERNAL_HAVE_EMSCRIPTEN_SYMBOLIZE
 
 // x86 specific tests.  Uses some inline assembler.
 extern "C" {
@@ -466,17 +481,6 @@ void ABSL_ATTRIBUTE_NOINLINE TestWithPCInsideInlineFunction() {
 }
 }
 
-// Test with a return address.
-void ABSL_ATTRIBUTE_NOINLINE TestWithReturnAddress() {
-#if defined(ABSL_HAVE_ATTRIBUTE_NOINLINE)
-  void *return_address = __builtin_return_address(0);
-  const char *symbol = TrySymbolize(return_address);
-  ABSL_RAW_CHECK(symbol != nullptr, "TestWithReturnAddress failed");
-  ABSL_RAW_CHECK(strcmp(symbol, "main") == 0, "TestWithReturnAddress failed");
-  std::cout << "TestWithReturnAddress passed" << std::endl;
-#endif
-}
-
 #if defined(__arm__) && ABSL_HAVE_ATTRIBUTE(target)
 // Test that we correctly identify bounds of Thumb functions on ARM.
 //
@@ -559,7 +563,6 @@ TEST(Symbolize, SymbolizeWithDemangling) {
 
 #endif  // !defined(ABSL_CONSUME_DLL)
 #else  // Symbolizer unimplemented
-
 TEST(Symbolize, Unimplemented) {
   char buf[64];
   EXPECT_FALSE(absl::Symbolize((void *)(&nonstatic_func), buf, sizeof(buf)));