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Diffstat (limited to 'third_party/abseil-cpp/absl/debugging/internal/stacktrace_emscripten-inl.inc')
-rw-r--r-- | third_party/abseil-cpp/absl/debugging/internal/stacktrace_emscripten-inl.inc | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/third_party/abseil-cpp/absl/debugging/internal/stacktrace_emscripten-inl.inc b/third_party/abseil-cpp/absl/debugging/internal/stacktrace_emscripten-inl.inc new file mode 100644 index 0000000000..0f44451438 --- /dev/null +++ b/third_party/abseil-cpp/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_ |