1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
|
// Copyright 2018 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.
//
// -----------------------------------------------------------------------------
// File: stacktrace.h
// -----------------------------------------------------------------------------
//
// This file contains routines to extract the current stack trace and associated
// stack frames. These functions are thread-safe and async-signal-safe.
//
// Note that stack trace functionality is platform dependent and requires
// additional support from the compiler/build system in most cases. (That is,
// this functionality generally only works on platforms/builds that have been
// specifically configured to support it.)
//
// Note: stack traces in Abseil that do not utilize a symbolizer will result in
// frames consisting of function addresses rather than human-readable function
// names. (See symbolize.h for information on symbolizing these values.)
#ifndef ABSL_DEBUGGING_STACKTRACE_H_
#define ABSL_DEBUGGING_STACKTRACE_H_
namespace absl {
inline namespace lts_2019_08_08 {
// GetStackFrames()
//
// Records program counter values for up to `max_depth` frames, skipping the
// most recent `skip_count` stack frames, and stores their corresponding values
// and sizes in `results` and `sizes` buffers. (Note that the frame generated
// for the `absl::GetStackFrames()` routine itself is also skipped.)
// routine itself.
//
// Example:
//
// main() { foo(); }
// foo() { bar(); }
// bar() {
// void* result[10];
// int sizes[10];
// int depth = absl::GetStackFrames(result, sizes, 10, 1);
// }
//
// The current stack frame would consist of three function calls: `bar()`,
// `foo()`, and then `main()`; however, since the `GetStackFrames()` call sets
// `skip_count` to `1`, it will skip the frame for `bar()`, the most recently
// invoked function call. It will therefore return two program counters and will
// produce values that map to the following function calls:
//
// result[0] foo()
// result[1] main()
//
// (Note: in practice, a few more entries after `main()` may be added to account
// for startup processes.)
//
// Corresponding stack frame sizes will also be recorded:
//
// sizes[0] 16
// sizes[1] 16
//
// (Stack frame sizes of `16` above are just for illustration purposes.)
//
// Stack frame sizes of 0 or less indicate that those frame sizes couldn't
// be identified.
//
// This routine may return fewer stack frame entries than are
// available. Also note that `result` and `sizes` must both be non-null.
extern int GetStackFrames(void** result, int* sizes, int max_depth,
int skip_count);
// GetStackFramesWithContext()
//
// Records program counter values obtained from a signal handler. Records
// program counter values for up to `max_depth` frames, skipping the most recent
// `skip_count` stack frames, and stores their corresponding values and sizes in
// `results` and `sizes` buffers. (Note that the frame generated for the
// `absl::GetStackFramesWithContext()` routine itself is also skipped.)
//
// The `uc` parameter, if non-null, should be a pointer to a `ucontext_t` value
// passed to a signal handler registered via the `sa_sigaction` field of a
// `sigaction` struct. (See
// http://man7.org/linux/man-pages/man2/sigaction.2.html.) The `uc` value may
// help a stack unwinder to provide a better stack trace under certain
// conditions. `uc` may safely be null.
//
// The `min_dropped_frames` output parameter, if non-null, points to the
// location to note any dropped stack frames, if any, due to buffer limitations
// or other reasons. (This value will be set to `0` if no frames were dropped.)
// The number of total stack frames is guaranteed to be >= skip_count +
// max_depth + *min_dropped_frames.
extern int GetStackFramesWithContext(void** result, int* sizes, int max_depth,
int skip_count, const void* uc,
int* min_dropped_frames);
// GetStackTrace()
//
// Records program counter values for up to `max_depth` frames, skipping the
// most recent `skip_count` stack frames, and stores their corresponding values
// in `results`. Note that this function is similar to `absl::GetStackFrames()`
// except that it returns the stack trace only, and not stack frame sizes.
//
// Example:
//
// main() { foo(); }
// foo() { bar(); }
// bar() {
// void* result[10];
// int depth = absl::GetStackTrace(result, 10, 1);
// }
//
// This produces:
//
// result[0] foo
// result[1] main
// .... ...
//
// `result` must not be null.
extern int GetStackTrace(void** result, int max_depth, int skip_count);
// GetStackTraceWithContext()
//
// Records program counter values obtained from a signal handler. Records
// program counter values for up to `max_depth` frames, skipping the most recent
// `skip_count` stack frames, and stores their corresponding values in
// `results`. (Note that the frame generated for the
// `absl::GetStackFramesWithContext()` routine itself is also skipped.)
//
// The `uc` parameter, if non-null, should be a pointer to a `ucontext_t` value
// passed to a signal handler registered via the `sa_sigaction` field of a
// `sigaction` struct. (See
// http://man7.org/linux/man-pages/man2/sigaction.2.html.) The `uc` value may
// help a stack unwinder to provide a better stack trace under certain
// conditions. `uc` may safely be null.
//
// The `min_dropped_frames` output parameter, if non-null, points to the
// location to note any dropped stack frames, if any, due to buffer limitations
// or other reasons. (This value will be set to `0` if no frames were dropped.)
// The number of total stack frames is guaranteed to be >= skip_count +
// max_depth + *min_dropped_frames.
extern int GetStackTraceWithContext(void** result, int max_depth,
int skip_count, const void* uc,
int* min_dropped_frames);
// SetStackUnwinder()
//
// Provides a custom function for unwinding stack frames that will be used in
// place of the default stack unwinder when invoking the static
// GetStack{Frames,Trace}{,WithContext}() functions above.
//
// The arguments passed to the unwinder function will match the
// arguments passed to `absl::GetStackFramesWithContext()` except that sizes
// will be non-null iff the caller is interested in frame sizes.
//
// If unwinder is set to null, we revert to the default stack-tracing behavior.
//
// *****************************************************************************
// WARNING
// *****************************************************************************
//
// absl::SetStackUnwinder is not suitable for general purpose use. It is
// provided for custom runtimes.
// Some things to watch out for when calling `absl::SetStackUnwinder()`:
//
// (a) The unwinder may be called from within signal handlers and
// therefore must be async-signal-safe.
//
// (b) Even after a custom stack unwinder has been unregistered, other
// threads may still be in the process of using that unwinder.
// Therefore do not clean up any state that may be needed by an old
// unwinder.
// *****************************************************************************
extern void SetStackUnwinder(int (*unwinder)(void** pcs, int* sizes,
int max_depth, int skip_count,
const void* uc,
int* min_dropped_frames));
// DefaultStackUnwinder()
//
// Records program counter values of up to `max_depth` frames, skipping the most
// recent `skip_count` stack frames, and stores their corresponding values in
// `pcs`. (Note that the frame generated for this call itself is also skipped.)
// This function acts as a generic stack-unwinder; prefer usage of the more
// specific `GetStack{Trace,Frames}{,WithContext}()` functions above.
//
// If you have set your own stack unwinder (with the `SetStackUnwinder()`
// function above, you can still get the default stack unwinder by calling
// `DefaultStackUnwinder()`, which will ignore any previously set stack unwinder
// and use the default one instead.
//
// Because this function is generic, only `pcs` is guaranteed to be non-null
// upon return. It is legal for `sizes`, `uc`, and `min_dropped_frames` to all
// be null when called.
//
// The semantics are the same as the corresponding `GetStack*()` function in the
// case where `absl::SetStackUnwinder()` was never called. Equivalents are:
//
// null sizes | non-nullptr sizes
// |==========================================================|
// null uc | GetStackTrace() | GetStackFrames() |
// non-null uc | GetStackTraceWithContext() | GetStackFramesWithContext() |
// |==========================================================|
extern int DefaultStackUnwinder(void** pcs, int* sizes, int max_depth,
int skip_count, const void* uc,
int* min_dropped_frames);
namespace debugging_internal {
// Returns true for platforms which are expected to have functioning stack trace
// implementations. Intended to be used for tests which want to exclude
// verification of logic known to be broken because stack traces are not
// working.
extern bool StackTraceWorksForTest();
} // namespace debugging_internal
} // inline namespace lts_2019_08_08
} // namespace absl
#endif // ABSL_DEBUGGING_STACKTRACE_H_
|
