// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
// Copyright (c) 2008, Google Inc.
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// ---
// 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).
//
// 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:
//   https://github.com/gperftools/gperftools/issues/86

#ifndef BASE_STACKTRACE_WIN32_INL_H_
#define BASE_STACKTRACE_WIN32_INL_H_
// Note: this file is included into stacktrace.cc more than once.
// Anything that should only be defined once should be here:

#include "config.h"
#include <windows.h>    // for GetProcAddress and GetModuleHandle
#include <assert.h>

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");

static int GetStackTrace_win32(void** result, int max_depth,
                               int skip_count) {
  if (!RtlCaptureStackBackTrace_fn) {
    // TODO(csilvers): should we log an error here?
    return 0;     // can't find a stacktrace with no function to call
  }
  return (int)RtlCaptureStackBackTrace_fn(skip_count + 3, max_depth,
                                          result, 0);
}

static int not_implemented(void) {
  assert(0 == "Not yet implemented");
  return 0;
}

static int GetStackFrames_win32(void** /* pcs */,
                                int* /* sizes */,
                                int /* max_depth */,
                                int /* skip_count */) {
  return not_implemented();
}

static int GetStackFramesWithContext_win32(void** result, int* sizes, int max_depth,
                                           int skip_count, const void *uc) {
  return not_implemented();
}

static int GetStackTraceWithContext_win32(void** result, int max_depth,
                                          int skip_count, const void *uc) {
  return not_implemented();
}


#endif  // BASE_STACKTRACE_WIN32_INL_H_
