base/debug/debug_on_start_win.h

   1 // Copyright (c) 2011 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_DEBUG_ON_START_WIN_H_
  10 #define BASE_DEBUG_DEBUG_ON_START_WIN_H_
  11
  12 #include "base/basictypes.h"
  13 #include "build/build_config.h"
  14
  15 // This only works on Windows. It's legal to include on other platforms, but
  16 // will be a NOP.
  17 #if defined(OS_WIN)
  18
  19 #ifndef DECLSPEC_SELECTANY
  20 #define DECLSPEC_SELECTANY  __declspec(selectany)
  21 #endif
  22
  23 namespace base {
  24 namespace debug {
  25
  26 // There is no way for this code, as currently implemented, to work across DLLs.
  27 // TODO(rvargas): It looks like we really don't use this code, at least not for
  28 // Chrome. Figure out if it's really worth implementing something simpler.
  29 #if !defined(COMPONENT_BUILD)
  30
  31 // Debug on start functions and data.
  32 class DebugOnStart {
  33  public:
  34   // Expected function type in the .CRT$XI* section.
  35   // Note: See VC\crt\src\internal.h for reference.
  36   typedef int  (__cdecl *PIFV)(void);
  37
  38   // Looks at the command line for kDebugOnStart argument. If found, it invokes
  39   // the debugger, if this fails, it crashes.
  40   static int __cdecl Init();
  41
  42   // Returns true if the 'argument' is present in the 'command_line'. It does
  43   // not use the CRT, only Kernel32 functions.
  44   static bool FindArgument(wchar_t* command_line, const char* argument);
  45 };
  46
  47 // Set the function pointer to our function to look for a crash on start. The
  48 // XIB section is started pretty early in the program initialization so in
  49 // theory it should be called before any user created global variable
  50 // initialization code and CRT initialization code.
  51 // Note: See VC\crt\src\defsects.inc and VC\crt\src\crt0.c for reference.
  52 #ifdef _WIN64
  53
  54 // "Fix" the segment. On x64, the .CRT segment is merged into the .rdata segment
  55 // so it contains const data only.
  56 #pragma const_seg(push, ".CRT$XIB")
  57 // Declare the pointer so the CRT will find it.
  58 extern const DebugOnStart::PIFV debug_on_start;
  59 DECLSPEC_SELECTANY const DebugOnStart::PIFV debug_on_start =
  60     &DebugOnStart::Init;
  61 // Fix back the segment.
  62 #pragma const_seg(pop)
  63
  64 #else  // _WIN64
  65
  66 // "Fix" the segment. On x86, the .CRT segment is merged into the .data segment
  67 // so it contains non-const data only.
  68 #pragma data_seg(push, ".CRT$XIB")
  69 // Declare the pointer so the CRT will find it.
  70 DECLSPEC_SELECTANY DebugOnStart::PIFV debug_on_start = &DebugOnStart::Init;
  71 // Fix back the segment.
  72 #pragma data_seg(pop)
  73
  74 #endif  // _WIN64
  75
  76 #endif  // defined(COMPONENT_BUILD)
  77
  78 }  // namespace debug
  79 }  // namespace base
  80
  81 #endif  // defined(OS_WIN)
  82
  83 #endif  // BASE_DEBUG_DEBUG_ON_START_WIN_H_