0302d1e5fa
gcc complains with:
```
'stacktraces_enabler' defined but not used [-Wunused-variable]
static int stacktraces_enabler = []() {
```
97 lines
3.3 KiB
C++
97 lines
3.3 KiB
C++
// Copyright 2000 - 2007 Google Inc.
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// All rights reserved.
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//
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// Author: Sanjay Ghemawat
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//
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// Portable implementation - just use glibc
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//
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// Note: The glibc implementation may cause a call to malloc.
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// This can cause a deadlock in HeapProfiler.
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#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_GENERIC_INL_H_
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#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_GENERIC_INL_H_
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#include <execinfo.h>
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#include <atomic>
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#include <cstring>
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#include "absl/debugging/stacktrace.h"
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#include "absl/base/attributes.h"
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// Sometimes, we can try to get a stack trace from within a stack
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// trace, because we don't block signals inside this code (which would be too
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// expensive: the two extra system calls per stack trace do matter here).
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// That can cause a self-deadlock.
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// Protect against such reentrant call by failing to get a stack trace.
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//
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// We use __thread here because the code here is extremely low level -- it is
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// called while collecting stack traces from within malloc and mmap, and thus
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// can not call anything which might call malloc or mmap itself.
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static __thread int recursive = 0;
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// The stack trace function might be invoked very early in the program's
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// execution (e.g. from the very first malloc if using tcmalloc). Also, the
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// glibc implementation itself will trigger malloc the first time it is called.
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// As such, we suppress usage of backtrace during this early stage of execution.
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static std::atomic<bool> disable_stacktraces(true); // Disabled until healthy.
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// Waiting until static initializers run seems to be late enough.
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// This file is included into stacktrace.cc so this will only run once.
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ABSL_ATTRIBUTE_UNUSED static int stacktraces_enabler = []() {
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void* unused_stack[1];
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// Force the first backtrace to happen early to get the one-time shared lib
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// loading (allocation) out of the way. After the first call it is much safer
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// to use backtrace from a signal handler if we crash somewhere later.
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backtrace(unused_stack, 1);
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disable_stacktraces.store(false, std::memory_order_relaxed);
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return 0;
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}();
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template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
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static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count,
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const void *ucp, int *min_dropped_frames) {
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if (recursive || disable_stacktraces.load(std::memory_order_relaxed)) {
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return 0;
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}
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++recursive;
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static_cast<void>(ucp); // Unused.
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static const int kStackLength = 64;
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void * stack[kStackLength];
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int size;
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size = backtrace(stack, kStackLength);
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skip_count++; // we want to skip the current frame as well
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int result_count = size - skip_count;
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if (result_count < 0)
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result_count = 0;
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if (result_count > max_depth)
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result_count = max_depth;
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for (int i = 0; i < result_count; i++)
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result[i] = stack[i + skip_count];
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if (IS_STACK_FRAMES) {
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// No implementation for finding out the stack frame sizes yet.
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memset(sizes, 0, sizeof(*sizes) * result_count);
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}
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if (min_dropped_frames != nullptr) {
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if (size - skip_count - max_depth > 0) {
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*min_dropped_frames = size - skip_count - max_depth;
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} else {
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*min_dropped_frames = 0;
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}
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}
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--recursive;
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return result_count;
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}
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namespace absl {
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namespace debugging_internal {
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bool StackTraceWorksForTest() {
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return true;
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}
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} // namespace debugging_internal
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} // namespace absl
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#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_GENERIC_INL_H_
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