Force crash on Mac10.9- in BreakDebugger()

base/debug/stack_trace_posix.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/debug/stack_trace.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <signal.h>
 #include <stddef.h>
@@ skipping 356 matching lines @@
     if ((i + 1) % 4 == 0)
       PrintToStderr("\n");
   }
   PrintToStderr("\n");
 #endif  // ARCH_CPU_X86_FAMILY
 #endif  // defined(OS_LINUX)
 
   PrintToStderr("[end of stack trace]\n");
 
 #if defined(OS_MACOSX) && !defined(OS_IOS)
-  if (::signal(signal, SIG_DFL) == SIG_ERR)

[dcheng, 2016/09/09 05:15:50]

Why is this change necessary as well?

[Xianzhu, 2016/09/09 05:20:13]

Without this, the forced crash will be ignored.

At least on Mac10.9, ::signal(signal, SIG_DFL) seems to just restore the
original signal handler but not to reraise the signal. Based on my test, if
::signal(signal, SIG_DFL) is successful, this function just returns, and nothing
happens. _exit(1) will let the program crash. 

-    _exit(1);
+  ::signal(signal, SIG_DFL);
+  _exit(1);
 #else
   // Non-Mac OSes should probably reraise the signal as well, but the Linux
   // sandbox tests break on CrOS devices.
   // https://code.google.com/p/chromium/issues/detail?id=551681
   _exit(1);
 #endif  // defined(OS_MACOSX) && !defined(OS_IOS)
 }
 
 class PrintBacktraceOutputHandler : public BacktraceOutputHandler {
  public:
@@ skipping 416 matching lines @@
     *ptr = *start;
     *start++ = ch;
   }
   return buf;
 }
 
 }  // namespace internal
 
 }  // namespace debug
 }  // namespace base