1// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5// Define the necessary code and global data to look for kDebugOnStart command
6// line argument. When the command line argument is detected, it invokes the
7// debugger, if no system-wide debugger is registered, a debug break is done.
8
9#ifndef BASE_DEBUG_ON_START_H_
10#define BASE_DEBUG_ON_START_H_
11
12#include "base/basictypes.h"
13
14// This only works on Windows.
15#if defined(OS_WIN)
16
17#ifndef DECLSPEC_SELECTANY
18#define DECLSPEC_SELECTANY  __declspec(selectany)
19#endif
20
21// Debug on start functions and data.
22class DebugOnStart {
23 public:
24  // Expected function type in the .CRT$XI* section.
25  // Note: See VC\crt\src\internal.h for reference.
26  typedef int  (__cdecl *PIFV)(void);
27
28  // Looks at the command line for kDebugOnStart argument. If found, it invokes
29  // the debugger, if this fails, it crashes.
30  static int __cdecl Init();
31
32  // Returns true if the 'argument' is present in the 'command_line'. It does
33  // not use the CRT, only Kernel32 functions.
34  static bool FindArgument(wchar_t* command_line, const char* argument);
35};
36
37// Set the function pointer to our function to look for a crash on start. The
38// XIB section is started pretty early in the program initialization so in
39// theory it should be called before any user created global variable
40// initialization code and CRT initialization code.
41// Note: See VC\crt\src\defsects.inc and VC\crt\src\crt0.c for reference.
42#ifdef _WIN64
43
44// "Fix" the segment. On x64, the .CRT segment is merged into the .rdata segment
45// so it contains const data only.
46#pragma const_seg(push, ".CRT$XIB")
47// Declare the pointer so the CRT will find it.
48extern const DebugOnStart::PIFV debug_on_start;
49DECLSPEC_SELECTANY const DebugOnStart::PIFV debug_on_start =
50    &DebugOnStart::Init;
51// Fix back the segment.
52#pragma const_seg(pop)
53
54#else  // _WIN64
55
56// "Fix" the segment. On x86, the .CRT segment is merged into the .data segment
57// so it contains non-const data only.
58#pragma data_seg(push, ".CRT$XIB")
59// Declare the pointer so the CRT will find it.
60DECLSPEC_SELECTANY DebugOnStart::PIFV debug_on_start = &DebugOnStart::Init;
61// Fix back the segment.
62#pragma data_seg(pop)
63
64#endif  // _WIN64
65#endif  // defined(OS_WIN)
66
67#endif  // BASE_DEBUG_ON_START_H_
68