/src/abseil-cpp/absl/debugging/stacktrace.cc

Source
// 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.

// Produce stack trace.
//
// There are three different ways we can try to get the stack trace:
//
// 1) Our hand-coded stack-unwinder.  This depends on a certain stack
//    layout, which is used by gcc (and those systems using a
//    gcc-compatible ABI) on x86 systems, at least since gcc 2.95.
//    It uses the frame pointer to do its work.
//
// 2) The libunwind library.  This is still in development, and as a
//    separate library adds a new dependency, but doesn't need a frame
//    pointer.  It also doesn't call malloc.
//
// 3) The gdb unwinder -- also the one used by the c++ exception code.
//    It's obviously well-tested, but has a fatal flaw: it can call
//    malloc() from the unwinder.  This is a problem because we're
//    trying to use the unwinder to instrument malloc().
//
// Note: if you add a new implementation here, make sure it works
// correctly when absl::GetStackTrace() is called with max_depth == 0.
// Some code may do that.

#include "absl/debugging/stacktrace.h"

#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>

#include <algorithm>
#include <atomic>
#include <iterator>

#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/internal/low_level_alloc.h"
#include "absl/base/optimization.h"
#include "absl/base/port.h"
#include "absl/debugging/internal/stacktrace_config.h"

#if defined(ABSL_STACKTRACE_INL_HEADER)
#include ABSL_STACKTRACE_INL_HEADER
#else
# error Cannot calculate stack trace: will need to write for your environment

# 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_riscv-inl.inc"
# include "absl/debugging/internal/stacktrace_unimplemented-inl.inc"
# include "absl/debugging/internal/stacktrace_win32-inl.inc"
# include "absl/debugging/internal/stacktrace_x86-inl.inc"
#endif

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace {

typedef int (*Unwinder)(void**, int*, int, int, const void*, int*);
std::atomic<Unwinder> custom;

template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
ABSL_ATTRIBUTE_ALWAYS_INLINE inline int Unwind(void** result, uintptr_t* frames,
                                               int* sizes, size_t max_depth,
                                               int skip_count, const void* uc,
                                               int* min_dropped_frames,
                                               bool unwind_with_fixup = true) {
  static constexpr size_t kMinPageSize = 4096;

  // Allow up to ~half a page, leaving some slack space for local variables etc.
  static constexpr size_t kMaxStackElements =
      (kMinPageSize / 2) / (sizeof(*frames) + sizeof(*sizes));

  // Allocate a buffer dynamically, using the signal-safe allocator.
  static constexpr auto allocate = [](size_t num_bytes) -> void* {
    base_internal::InitSigSafeArena();
    return base_internal::LowLevelAlloc::AllocWithArena(
        num_bytes, base_internal::SigSafeArena());
  };

  uintptr_t frames_stackbuf[kMaxStackElements];
  int sizes_stackbuf[kMaxStackElements];

  // We only need to free the buffers if we allocated them with the signal-safe
  // allocator.
  bool must_free_frames = false;
  bool must_free_sizes = false;

  unwind_with_fixup =
      unwind_with_fixup && internal_stacktrace::ShouldFixUpStack();

#ifdef _WIN32
  if (unwind_with_fixup) {
    // TODO(b/434184677): Fixups are flaky and not supported on Windows
    unwind_with_fixup = false;
#ifndef NDEBUG
    abort();
#endif
  }
#endif

  if (unwind_with_fixup) {
    // Some implementations of FixUpStack may need to be passed frame
    // information from Unwind, even if the caller doesn't need that
    // information. We allocate the necessary buffers for such implementations
    // here.

    if (frames == nullptr) {
      if (max_depth <= std::size(frames_stackbuf)) {
        frames = frames_stackbuf;
      } else {
        frames = static_cast<uintptr_t*>(allocate(max_depth * sizeof(*frames)));
        must_free_frames = true;
      }
    }

    if (sizes == nullptr) {
      if (max_depth <= std::size(sizes_stackbuf)) {
        sizes = sizes_stackbuf;
      } else {
        sizes = static_cast<int*>(allocate(max_depth * sizeof(*sizes)));
        must_free_sizes = true;
      }
    }
  }

  Unwinder g = custom.load(std::memory_order_acquire);
  size_t size;
  // Add 1 to skip count for the unwinder function itself
  ++skip_count;
  if (g != nullptr) {
    size = static_cast<size_t>((*g)(result, sizes, static_cast<int>(max_depth),
                                    skip_count, uc, min_dropped_frames));
    // Frame pointers aren't returned by existing hooks, so clear them.
    if (frames != nullptr) {
      std::fill(frames, frames + size, uintptr_t());
    }
  } else {
    size = static_cast<size_t>(
        unwind_with_fixup
            ? UnwindImpl<true, IS_WITH_CONTEXT>(
                  result, frames, sizes, static_cast<int>(max_depth),
                  skip_count, uc, min_dropped_frames)
            : UnwindImpl<IS_STACK_FRAMES, IS_WITH_CONTEXT>(
                  result, frames, sizes, static_cast<int>(max_depth),
                  skip_count, uc, min_dropped_frames));
  }
  if (unwind_with_fixup) {
    internal_stacktrace::FixUpStack(result, frames, sizes, max_depth, size);
  }

  if (must_free_sizes) {
    base_internal::LowLevelAlloc::Free(sizes);
  }

  if (must_free_frames) {
    base_internal::LowLevelAlloc::Free(frames);
  }

  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
  return static_cast<int>(size);
}

}  // anonymous namespace

ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
internal_stacktrace::GetStackFrames(void** result, uintptr_t* frames,
                                    int* sizes, int max_depth, int skip_count) {
  return Unwind<true, false>(result, frames, sizes,
                             static_cast<size_t>(max_depth), skip_count,
                             nullptr, nullptr);
}

ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
internal_stacktrace::GetStackFramesWithContext(void** result, uintptr_t* frames,
                                               int* sizes, int max_depth,
                                               int skip_count, const void* uc,
                                               int* min_dropped_frames) {
  return Unwind<true, true>(result, frames, sizes,
                            static_cast<size_t>(max_depth), skip_count, uc,
                            min_dropped_frames);
}

ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
internal_stacktrace::GetStackTraceNoFixup(void** result, int max_depth,
                                          int skip_count) {
  return Unwind<false, false>(result, nullptr, nullptr,
                              static_cast<size_t>(max_depth), skip_count,
                              nullptr, nullptr, /*unwind_with_fixup=*/false);
}

ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int GetStackTrace(
    void** result, int max_depth, int skip_count) {
  return Unwind<false, false>(result, nullptr, nullptr,
                              static_cast<size_t>(max_depth), skip_count,
                              nullptr, nullptr);
}

ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
GetStackTraceWithContext(void** result, int max_depth, int skip_count,
                         const void* uc, int* min_dropped_frames) {
  return Unwind<false, true>(result, nullptr, nullptr,
                             static_cast<size_t>(max_depth), skip_count, uc,
                             min_dropped_frames);
}

void SetStackUnwinder(Unwinder w) {
  custom.store(w, std::memory_order_release);
}

ABSL_ATTRIBUTE_ALWAYS_INLINE static inline int DefaultStackUnwinderImpl(
    void** pcs, uintptr_t* frames, int* sizes, int depth, int skip,
    const void* uc, int* min_dropped_frames) {
  skip++;  // For this function
  decltype(&UnwindImpl<false, false>) f;
  if (sizes == nullptr) {
    if (uc == nullptr) {
      f = &UnwindImpl<false, false>;
    } else {
      f = &UnwindImpl<false, true>;
    }
  } else {
    if (uc == nullptr) {
      f = &UnwindImpl<true, false>;
    } else {
      f = &UnwindImpl<true, true>;
    }
  }
  return (*f)(pcs, frames, sizes, depth, skip, uc, min_dropped_frames);
}

ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
internal_stacktrace::DefaultStackUnwinder(void** pcs, uintptr_t* frames,
                                          int* sizes, int depth, int skip,
                                          const void* uc,
                                          int* min_dropped_frames) {
  int n = DefaultStackUnwinderImpl(pcs, frames, sizes, depth, skip, uc,
                                   min_dropped_frames);
  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
  return n;
}

ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int DefaultStackUnwinder(
    void** pcs, int* sizes, int depth, int skip, const void* uc,
    int* min_dropped_frames) {
  int n = DefaultStackUnwinderImpl(pcs, nullptr, sizes, depth, skip, uc,
                                   min_dropped_frames);
  ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
  return n;
}

ABSL_ATTRIBUTE_WEAK bool internal_stacktrace::ShouldFixUpStack() {
  return false;
}

// Fixes up the stack trace of the current thread, in the first `depth` frames
// of each buffer. The buffers need to be larger than `depth`, to accommodate
// any newly inserted elements. `depth` is updated to reflect the new number of
// elements valid across all the buffers. (It is therefore recommended that all
// buffer sizes be equal.)
//
// The `frames` and `sizes` parameters denote the bounds of the stack frame
// corresponding to each instruction pointer in the `pcs`.
// Any elements inside these buffers may be zero or null, in which case that
// information is assumed to be absent/unavailable.
ABSL_ATTRIBUTE_WEAK void internal_stacktrace::FixUpStack(void**, uintptr_t*,
                                                         int*, size_t,
                                                         size_t&) {}

ABSL_NAMESPACE_END
}  // namespace absl

Coverage Report

Created: 2025-10-28 06:50

Line	Count	Source
1		// Copyright 2017 The Abseil Authors.
2		//
3		// Licensed under the Apache License, Version 2.0 (the "License");
4		// you may not use this file except in compliance with the License.
5		// You may obtain a copy of the License at
6		//
7		// https://www.apache.org/licenses/LICENSE-2.0
8		//
9		// Unless required by applicable law or agreed to in writing, software
10		// distributed under the License is distributed on an "AS IS" BASIS,
11		// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12		// See the License for the specific language governing permissions and
13		// limitations under the License.
14
15		// Produce stack trace.
16		//
17		// There are three different ways we can try to get the stack trace:
18		//
19		// 1) Our hand-coded stack-unwinder. This depends on a certain stack
20		// layout, which is used by gcc (and those systems using a
21		// gcc-compatible ABI) on x86 systems, at least since gcc 2.95.
22		// It uses the frame pointer to do its work.
23		//
24		// 2) The libunwind library. This is still in development, and as a
25		// separate library adds a new dependency, but doesn't need a frame
26		// pointer. It also doesn't call malloc.
27		//
28		// 3) The gdb unwinder -- also the one used by the c++ exception code.
29		// It's obviously well-tested, but has a fatal flaw: it can call
30		// malloc() from the unwinder. This is a problem because we're
31		// trying to use the unwinder to instrument malloc().
32		//
33		// Note: if you add a new implementation here, make sure it works
34		// correctly when absl::GetStackTrace() is called with max_depth == 0.
35		// Some code may do that.
36
37		#include "absl/debugging/stacktrace.h"
38
39		#include <stddef.h>
40		#include <stdint.h>
41		#include <stdlib.h>
42
43		#include <algorithm>
44		#include <atomic>
45		#include <iterator>
46
47		#include "absl/base/attributes.h"
48		#include "absl/base/config.h"
49		#include "absl/base/internal/low_level_alloc.h"
50		#include "absl/base/optimization.h"
51		#include "absl/base/port.h"
52		#include "absl/debugging/internal/stacktrace_config.h"
53
54		#if defined(ABSL_STACKTRACE_INL_HEADER)
55		#include ABSL_STACKTRACE_INL_HEADER
56		#else
57		# error Cannot calculate stack trace: will need to write for your environment
58
59		# include "absl/debugging/internal/stacktrace_aarch64-inl.inc"
60		# include "absl/debugging/internal/stacktrace_arm-inl.inc"
61		# include "absl/debugging/internal/stacktrace_emscripten-inl.inc"
62		# include "absl/debugging/internal/stacktrace_generic-inl.inc"
63		# include "absl/debugging/internal/stacktrace_powerpc-inl.inc"
64		# include "absl/debugging/internal/stacktrace_riscv-inl.inc"
65		# include "absl/debugging/internal/stacktrace_unimplemented-inl.inc"
66		# include "absl/debugging/internal/stacktrace_win32-inl.inc"
67		# include "absl/debugging/internal/stacktrace_x86-inl.inc"
68		#endif
69
70		namespace absl {
71		ABSL_NAMESPACE_BEGIN
72		namespace {
73
74		typedef int (Unwinder)(void, int, int, int, const void, int);
75		std::atomic<Unwinder> custom;
76
77		template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT>
78		ABSL_ATTRIBUTE_ALWAYS_INLINE inline int Unwind(void** result, uintptr_t* frames,
79		int* sizes, size_t max_depth,
80		int skip_count, const void* uc,
81		int* min_dropped_frames,
82	0	bool unwind_with_fixup = true) {
83	0	static constexpr size_t kMinPageSize = 4096;
84
85		// Allow up to ~half a page, leaving some slack space for local variables etc.
86	0	static constexpr size_t kMaxStackElements =
87	0	(kMinPageSize / 2) / (sizeof(frames) + sizeof(sizes));
88
89		// Allocate a buffer dynamically, using the signal-safe allocator.
90	0	static constexpr auto allocate = [](size_t num_bytes) -> void* {
91	0	base_internal::InitSigSafeArena();
92	0	return base_internal::LowLevelAlloc::AllocWithArena(
93	0	num_bytes, base_internal::SigSafeArena());
94	0	}; Unexecuted instantiation: stacktrace.cc:absl::(anonymous namespace)::Unwind<true, false>(void*, unsigned long, int, unsigned long, int, void const, int, bool)::{lambda(unsigned long)#1}::operator()(unsigned long) const Unexecuted instantiation: stacktrace.cc:absl::(anonymous namespace)::Unwind<true, true>(void, unsigned long, int, unsigned long, int, void const, int, bool)::{lambda(unsigned long)#1}::operator()(unsigned long) const Unexecuted instantiation: stacktrace.cc:absl::(anonymous namespace)::Unwind<false, false>(void, unsigned long, int, unsigned long, int, void const, int, bool)::{lambda(unsigned long)#1}::operator()(unsigned long) const Unexecuted instantiation: stacktrace.cc:absl::(anonymous namespace)::Unwind<false, true>(void, unsigned long, int, unsigned long, int, void const, int*, bool)::{lambda(unsigned long)#1}::operator()(unsigned long) const
95
96	0	uintptr_t frames_stackbuf[kMaxStackElements];
97	0	int sizes_stackbuf[kMaxStackElements];
98
99		// We only need to free the buffers if we allocated them with the signal-safe
100		// allocator.
101	0	bool must_free_frames = false;
102	0	bool must_free_sizes = false;
103
104	0	unwind_with_fixup =
105	0	unwind_with_fixup && internal_stacktrace::ShouldFixUpStack();
106
107		#ifdef _WIN32
108		if (unwind_with_fixup) {
109		// TODO(b/434184677): Fixups are flaky and not supported on Windows
110		unwind_with_fixup = false;
111		#ifndef NDEBUG
112		abort();
113		#endif
114		}
115		#endif
116
117	0	if (unwind_with_fixup) {
118		// Some implementations of FixUpStack may need to be passed frame
119		// information from Unwind, even if the caller doesn't need that
120		// information. We allocate the necessary buffers for such implementations
121		// here.
122
123	0	if (frames == nullptr) {
124	0	if (max_depth <= std::size(frames_stackbuf)) {
125	0	frames = frames_stackbuf;
126	0	} else {
127	0	frames = static_cast<uintptr_t>(allocate(max_depth sizeof(*frames)));
128	0	must_free_frames = true;
129	0	}
130	0	}
131
132	0	if (sizes == nullptr) {
133	0	if (max_depth <= std::size(sizes_stackbuf)) {
134	0	sizes = sizes_stackbuf;
135	0	} else {
136	0	sizes = static_cast<int>(allocate(max_depth sizeof(*sizes)));
137	0	must_free_sizes = true;
138	0	}
139	0	}
140	0	}
141
142	0	Unwinder g = custom.load(std::memory_order_acquire);
143	0	size_t size;
144		// Add 1 to skip count for the unwinder function itself
145	0	++skip_count;
146	0	if (g != nullptr) {
147	0	size = static_cast<size_t>((*g)(result, sizes, static_cast<int>(max_depth),
148	0	skip_count, uc, min_dropped_frames));
149		// Frame pointers aren't returned by existing hooks, so clear them.
150	0	if (frames != nullptr) {
151	0	std::fill(frames, frames + size, uintptr_t());
152	0	}
153	0	} else {
154	0	size = static_cast<size_t>(
155	0	unwind_with_fixup
156	0	? UnwindImpl<true, IS_WITH_CONTEXT>(
157	0	result, frames, sizes, static_cast<int>(max_depth),
158	0	skip_count, uc, min_dropped_frames)
159	0	: UnwindImpl<IS_STACK_FRAMES, IS_WITH_CONTEXT>(
160	0	result, frames, sizes, static_cast<int>(max_depth),
161	0	skip_count, uc, min_dropped_frames));
162	0	}
163	0	if (unwind_with_fixup) {
164	0	internal_stacktrace::FixUpStack(result, frames, sizes, max_depth, size);
165	0	}
166
167	0	if (must_free_sizes) {
168	0	base_internal::LowLevelAlloc::Free(sizes);
169	0	}
170
171	0	if (must_free_frames) {
172	0	base_internal::LowLevelAlloc::Free(frames);
173	0	}
174
175	0	ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
176	0	return static_cast<int>(size);
177	0	} Unexecuted instantiation: stacktrace.cc:int absl::(anonymous namespace)::Unwind<true, false>(void*, unsigned long, int, unsigned long, int, void const, int, bool) Unexecuted instantiation: stacktrace.cc:int absl::(anonymous namespace)::Unwind<true, true>(void, unsigned long, int, unsigned long, int, void const, int, bool) Unexecuted instantiation: stacktrace.cc:int absl::(anonymous namespace)::Unwind<false, false>(void, unsigned long, int, unsigned long, int, void const, int, bool) Unexecuted instantiation: stacktrace.cc:int absl::(anonymous namespace)::Unwind<false, true>(void, unsigned long, int, unsigned long, int, void const, int*, bool)
178
179		} // anonymous namespace
180
181		ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
182		internal_stacktrace::GetStackFrames(void** result, uintptr_t* frames,
183	0	int* sizes, int max_depth, int skip_count) {
184	0	return Unwind<true, false>(result, frames, sizes,
185	0	static_cast<size_t>(max_depth), skip_count,
186	0	nullptr, nullptr);
187	0	}
188
189		ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
190		internal_stacktrace::GetStackFramesWithContext(void** result, uintptr_t* frames,
191		int* sizes, int max_depth,
192		int skip_count, const void* uc,
193	0	int* min_dropped_frames) {
194	0	return Unwind<true, true>(result, frames, sizes,
195	0	static_cast<size_t>(max_depth), skip_count, uc,
196	0	min_dropped_frames);
197	0	}
198
199		ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
200		internal_stacktrace::GetStackTraceNoFixup(void** result, int max_depth,
201	0	int skip_count) {
202	0	return Unwind<false, false>(result, nullptr, nullptr,
203	0	static_cast<size_t>(max_depth), skip_count,
204	0	nullptr, nullptr, /unwind_with_fixup=/false);
205	0	}
206
207		ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int GetStackTrace(
208	0	void** result, int max_depth, int skip_count) {
209	0	return Unwind<false, false>(result, nullptr, nullptr,
210	0	static_cast<size_t>(max_depth), skip_count,
211	0	nullptr, nullptr);
212	0	}
213
214		ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
215		GetStackTraceWithContext(void** result, int max_depth, int skip_count,
216	0	const void* uc, int* min_dropped_frames) {
217	0	return Unwind<false, true>(result, nullptr, nullptr,
218	0	static_cast<size_t>(max_depth), skip_count, uc,
219	0	min_dropped_frames);
220	0	}
221
222	0	void SetStackUnwinder(Unwinder w) {
223	0	custom.store(w, std::memory_order_release);
224	0	}
225
226		ABSL_ATTRIBUTE_ALWAYS_INLINE static inline int DefaultStackUnwinderImpl(
227		void** pcs, uintptr_t* frames, int* sizes, int depth, int skip,
228	0	const void* uc, int* min_dropped_frames) {
229	0	skip++; // For this function
230	0	decltype(&UnwindImpl<false, false>) f;
231	0	if (sizes == nullptr) {
232	0	if (uc == nullptr) {
233	0	f = &UnwindImpl<false, false>;
234	0	} else {
235	0	f = &UnwindImpl<false, true>;
236	0	}
237	0	} else {
238	0	if (uc == nullptr) {
239	0	f = &UnwindImpl<true, false>;
240	0	} else {
241	0	f = &UnwindImpl<true, true>;
242	0	}
243	0	}
244	0	return (*f)(pcs, frames, sizes, depth, skip, uc, min_dropped_frames);
245	0	}
246
247		ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int
248		internal_stacktrace::DefaultStackUnwinder(void** pcs, uintptr_t* frames,
249		int* sizes, int depth, int skip,
250		const void* uc,
251	0	int* min_dropped_frames) {
252	0	int n = DefaultStackUnwinderImpl(pcs, frames, sizes, depth, skip, uc,
253	0	min_dropped_frames);
254	0	ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
255	0	return n;
256	0	}
257
258		ABSL_ATTRIBUTE_NOINLINE ABSL_ATTRIBUTE_NO_TAIL_CALL int DefaultStackUnwinder(
259		void** pcs, int* sizes, int depth, int skip, const void* uc,
260	0	int* min_dropped_frames) {
261	0	int n = DefaultStackUnwinderImpl(pcs, nullptr, sizes, depth, skip, uc,
262	0	min_dropped_frames);
263	0	ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
264	0	return n;
265	0	}
266
267	0	ABSL_ATTRIBUTE_WEAK bool internal_stacktrace::ShouldFixUpStack() {
268	0	return false;
269	0	}
270
271		// Fixes up the stack trace of the current thread, in the first `depth` frames
272		// of each buffer. The buffers need to be larger than `depth`, to accommodate
273		// any newly inserted elements. `depth` is updated to reflect the new number of
274		// elements valid across all the buffers. (It is therefore recommended that all
275		// buffer sizes be equal.)
276		//
277		// The `frames` and `sizes` parameters denote the bounds of the stack frame
278		// corresponding to each instruction pointer in the `pcs`.
279		// Any elements inside these buffers may be zero or null, in which case that
280		// information is assumed to be absent/unavailable.
281		ABSL_ATTRIBUTE_WEAK void internal_stacktrace::FixUpStack(void*, uintptr_t,
282		int*, size_t,
283	0	size_t&) {}
284
285		ABSL_NAMESPACE_END
286		} // namespace absl