[Mac] Override abort() to crash into breakpad.

chrome/app/breakpad_mac.mm

 // 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.
 
 #import "chrome/app/breakpad_mac.h"
 
 #include <CoreFoundation/CoreFoundation.h>
 #import <Foundation/Foundation.h>
 
 #include "base/auto_reset.h"
@@ skipping 120 matching lines @@
   DumpHelper() {}
 
   virtual void ThreadMain() OVERRIDE {
     base::PlatformThread::SetName("CrDumpHelper");
     BreakpadGenerateAndSendReport(gBreakpadRef);
   }
 
   DISALLOW_COPY_AND_ASSIGN(DumpHelper);
 };
 
+void SIGABRTHandler(int signal) {
+  // The OSX abort() (link below) masks all signals for the process,
+  // and all except SIGABRT for the thread.  SIGABRT will be masked
+  // when the SIGABRT is sent, which means at this point only SIGKILL
+  // and SIGSTOP can be delivered.  Unmask others so that the code
+  // below crashes as desired.
+  //
+  // http://www.opensource.apple.com/source/Libc/Libc-825.26/stdlib/FreeBSD/abort.c
+  sigset_t mask;
+  sigemptyset(&mask);
+  sigaddset(&mask, signal);
+  pthread_sigmask(SIG_SETMASK, &mask, NULL);
+
+  // Most interesting operations are not safe in a signal handler, just crash.
+  char* volatile death_ptr = NULL;
+  *death_ptr = '!';
+}
+
 }  // namespace
 
 bool IsCrashReporterEnabled() {
   return gBreakpadRef != NULL;
 }
 
 // Only called for a branded build of Chrome.app.
 void InitCrashReporter() {
   DCHECK(!gBreakpadRef);
   base::mac::ScopedNSAutoreleasePool autorelease_pool;
@@ skipping 116 matching lines @@
 
   if (!is_browser) {
     // Get the guid from the command line switch.
     std::string guid =
         command_line->GetSwitchValueASCII(switches::kEnableCrashReporter);
     child_process_logging::SetClientId(guid);
   }
 
   logging::SetLogMessageHandler(&FatalMessageHandler);
   logging::SetDumpWithoutCrashingFunction(&DumpHelper::DumpWithoutCrashing);
+
+  // abort() sends SIGABRT, which breakpad does not intercept.
+  // Register a signal handler to crash in a way breakpad will
+  // intercept.

[Nico, 2013/05/23 21:27:50]

Why doesn't breakpad do that?

[Scott Hess - ex-Googler, 2013/05/23 21:32:59]

One day on the bug, Mark said "Mac Breakpad doesn’t and shouldn’t deal with
things in terms of POSIX signals."

[insert picture of doggie scientist here.]

+  struct sigaction sigact;
+  memset(&sigact, 0, sizeof(sigact));
+  sigact.sa_handler = SIGABRTHandler;
+  CHECK(0 == sigaction(SIGABRT, &sigact, NULL));
 }
 
 void InitCrashProcessInfo() {
   if (gBreakpadRef == NULL) {
     return;
   }
 
   // Determine the process type.
   NSString* process_type = @"browser";
   std::string process_type_switch =
       CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
           switches::kProcessType);
   if (!process_type_switch.empty()) {
     process_type = base::SysUTF8ToNSString(process_type_switch);
   }
 
 #if !defined(DISABLE_NACL)
   if (process_type_switch == switches::kNaClLoaderProcess) {
     BreakpadSetFilterCallback(gBreakpadRef, NaClBreakpadCrashFilter, NULL);
   }
 #endif
 
   // Store process type in crash dump.
   SetCrashKeyValue(@"ptype", process_type);
 }