Bug 644707 - Avoid calling system abort(), generate useful stack traces through a manual segfault instead. r=ted

memory/mozalloc/mozalloc_abort.cpp

@@ -47,6 +47,7 @@
 #  include <windows.h>          // for DebugBreak
 #elif defined(XP_UNIX)
 #  include <unistd.h>           // for _exit
+#  include <signal.h>
 #endif
 
 #if defined(XP_WIN) || defined(XP_OS2)
@@ -72,19 +73,39 @@ mozalloc_abort(const char* const msg)
     fputs(msg, stderr);
     fputs("\n", stderr);
 
-#if defined(XP_UNIX) && !defined(XP_MACOSX)
-    abort();
-#elif defined(_MSC_VER)
+#if defined(_MSC_VER)
     __debugbreak();
 #elif defined(XP_WIN)
     DebugBreak();
 #endif
-    // abort() doesn't trigger breakpad on Mac, "fall through" to the
-    // fail-safe code
 
-    // Still haven't aborted?  Try dereferencing null.
+    // On *NIX platforms the prefered way to abort is by touching bad memory,
+    // since this generates a stack trace inside our own code (avoiding
+    // problems with starting the trace inside libc, where we might not have
+    // symbols and can get lost).
+
     TouchBadMemory();
 
+    // If we haven't aborted yet, we can try to raise SIGABRT which might work
+    // on some *NIXs, but not OS X (it doesn't trigger breakpad there).
+    // Note that we don't call abort(), since raise is likelier to give us
+    // useful stack data, and also since abort() is redirected to call this
+    // function (see below).
+#if defined(XP_UNIX) && !defined(XP_MACOSX)
+    raise(SIGABRT);
+#endif
+
     // Still haven't aborted?  Try _exit().
     _exit(127);
 }
+
+#if defined(XP_UNIX)
+// Define abort() here, so that it is used instead of the system abort(). This
+// lets us control the behavior when aborting, in order to get better results
+// on *NIX platfrorms. See mozalloc_abort for details.
+void abort(void)
+{
+  mozalloc_abort("Redirecting call to abort() to mozalloc_abort\n");
+}
+#endif
+