// 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 // // http://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. // // Produces a stack trace for Windows. Normally, one could use // stacktrace_x86-inl.h or stacktrace_x86_64-inl.h -- and indeed, that // should work for binaries compiled using MSVC in "debug" mode. // However, in "release" mode, Windows uses frame-pointer // optimization, which makes getting a stack trace very difficult. // // There are several approaches one can take. One is to use Windows // intrinsics like StackWalk64. These can work, but have restrictions // on how successful they can be. Another attempt is to write a // version of stacktrace_x86-inl.h that has heuristic support for // dealing with FPO, similar to what WinDbg does (see // http://www.nynaeve.net/?p=97). There are (non-working) examples of // these approaches, complete with TODOs, in stacktrace_win32-inl.h#1 // // The solution we've ended up doing is to call the undocumented // windows function RtlCaptureStackBackTrace, which probably doesn't // work with FPO but at least is fast, and doesn't require a symbol // server. // // This code is inspired by a patch from David Vitek: // http://code.google.com/p/google-perftools/issues/detail?id=83 #ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_ #define ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_ #include <windows.h> // for GetProcAddress and GetModuleHandle #include <cassert> typedef USHORT NTAPI RtlCaptureStackBackTrace_Function( IN ULONG frames_to_skip, IN ULONG frames_to_capture, OUT PVOID *backtrace, OUT PULONG backtrace_hash); // Load the function we need at static init time, where we don't have // to worry about someone else holding the loader's lock. static RtlCaptureStackBackTrace_Function* const RtlCaptureStackBackTrace_fn = (RtlCaptureStackBackTrace_Function*) GetProcAddress(GetModuleHandleA("ntdll.dll"), "RtlCaptureStackBackTrace"); 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) { int n = 0; if (!RtlCaptureStackBackTrace_fn) { // can't find a stacktrace with no function to call } else { n = (int)RtlCaptureStackBackTrace_fn(skip_count + 2, max_depth, result, 0); } if (IS_STACK_FRAMES) { // No implementation for finding out the stack frame sizes yet. memset(sizes, 0, sizeof(*sizes) * n); } if (min_dropped_frames != nullptr) { // Not implemented. *min_dropped_frames = 0; } return n; } namespace absl { namespace debugging_internal { bool StackTraceWorksForTest() { return false; } } // namespace debugging_internal } // namespace absl #endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_