@ -1,5 +1,4 @@
//
// Copyright 2017 The Abseil Authors.
// 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.
@ -13,26 +12,37 @@
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Routines to extract the current stack trace. These functions are
// thread-safe and async-signal-safe.
// -----------------------------------------------------------------------------
// 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 many cases. (That is,
// this generally only works on platforms/builds that have been specifically
// configured to support it.)
// 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 {
// Skips the most recent "skip_count" stack frames (also skips the
// frame generated for the "absl::GetStackFrames" routine itself), and then
// records the pc values for up to the next "max_depth" frames in
// "result", and the corresponding stack frame sizes in "sizes".
// Returns the number of values recorded in "result"/"sizes".
// 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() {
@ -41,41 +51,66 @@ namespace absl {
// int depth = absl::GetStackFrames(result, sizes, 10, 1);
// }
//
// The absl::GetStackFrames call will skip the frame for "bar". It will
// return 2 and will produce pc values that map to the following
// procedures:
// result[0] foo
// result[1] main
// (Actually, there may be a few more entries after "main" to account for
// startup procedures.)
// And corresponding stack frame sizes will also be recorded:
// 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 `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.
// 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 ) ;
// Same as above, but to be used from a signal handler. The "uc" parameter
// should be the pointer to ucontext_t which was passed as the 3rd parameter
// to sa_sigaction signal handler. It may help the unwinder to get a
// better stack trace under certain conditions. The "uc" may safely be null.
//
// If min_dropped_frames is not null, stores in *min_dropped_frames a
// lower bound on the number of dropped stack frames. The stored value is
// guaranteed to be >= 0. The number of real stack frames is guaranteed to
// be >= skip_count + max_depth + *min_dropped_frames.
// 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 ) ;
// This is similar to the absl::GetStackFrames routine, except that it returns
// the stack trace only, and not the stack frame sizes as well.
// 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() {
@ -84,42 +119,57 @@ extern int GetStackFramesWithContext(void** result, int* sizes, int max_depth,
// }
//
// This produces:
//
// result[0] foo
// result[1] main
// .... ...
//
// "result" must not be null.
// `result` must not be null.
extern int GetStackTrace ( void * * result , int max_depth , int skip_count ) ;
// Same as above, but to be used from a signal handler. The "uc" parameter
// should be the pointer to ucontext_t which was passed as the 3rd parameter
// to sa_sigaction signal handler. It may help the unwinder to get a
// better stack trace under certain conditions. The "uc" may safely be null.
//
// If min_dropped_frames is not null, stores in *min_dropped_frames a
// lower bound on the number of dropped stack frames. The stored value is
// guaranteed to be >= 0. The number of real stack frames is guaranteed to
// be >= skip_count + max_depth + *min_dropped_frames.
// 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 ) ;
// Call this to provide a custom function for unwinding stack frames
// that will be used every time someone invokes one of the static
// 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
// arguments passed to ` absl::GetStackFramesWithContext()` except that sizes
// will be non-null iff the caller is interested in frame sizes.
//
// If unwinder is null, we revert to the default stack-tracing behavior.
// If unwinder is set to null, we revert to the default stack-tracing behavior.
//
// ****************************************************************
// WARNINGS
// *****************************************************************************
// 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:
// 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.
@ -128,23 +178,31 @@ extern int GetStackTraceWithContext(void** result, int max_depth,
// 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 ) ) ;
// Function that exposes built-in stack-unwinding behavior, ignoring
// any calls to absl::SetStackUnwinder().
// 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.
//
// pcs must NOT be null.
// 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.
//
// sizes may be null.
// uc may be null.
// min_dropped_frames may be null .
// 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:
// 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
// |==========================================================|
Abseil Team
7 years ago
committed by
jueminyang