bool Push(int i) {
   while (!mWriting.compareExchange(false, true)) {
   }
   mDQ.PushFront(reinterpret_cast<void*>(static_cast<uintptr_t>(i)));
   mWriting = false;
   return true;
 }

MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE MOZ_FORMAT_PRINTF(3, 4) void
MOZ_CrashPrintf(const char* aFilename, int aLine, const char* aFormat, ...)
#endif
{
  if (!sCrashing.compareExchange(false, true)) {
    // In the unlikely event of a race condition, skip
    // setting the crash reason and just crash safely.
    MOZ_REALLY_CRASH(aLine);
  }
  va_list aArgs;
  va_start(aArgs, aFormat);
  int ret = vsnprintf(sPrintfCrashReason, sPrintfCrashReasonSize,
                      aFormat, aArgs);
  va_end(aArgs);
  MOZ_RELEASE_ASSERT(ret >= 0 && size_t(ret) < sPrintfCrashReasonSize,
    "Could not write the explanation string to the supplied buffer!");
#ifdef DEBUG
  MOZ_ReportCrash(sPrintfCrashReason, aFilename, aLine);
#endif
  gMozCrashReason = sPrintfCrashReason;
  MOZ_REALLY_CRASH(aLine);
}

static void
UnixExceptionHandler(int signum, siginfo_t* info, void* context)
{
    // Make absolutely sure we can only get here once.
    if (sHandlingException.compareExchange(false, true)) {
        // Restore the previous handler. We're going to forward to it
        // anyway, and if we crash while doing so we don't want to hang.
        MOZ_ALWAYS_FALSE(sigaction(SIGSEGV, &sPrevSEGVHandler, nullptr));

        MOZ_ASSERT(signum == SIGSEGV && info->si_signo == SIGSEGV);

        if (info->si_code == SEGV_ACCERR) {
            // Get the address that the offending code tried to access.
            uintptr_t address = uintptr_t(info->si_addr);

            // If the faulting address is in one of our protected regions, we
            // want to annotate the crash to make it stand out from the crowd.
            if (sProtectedRegions.isProtected(address)) {
                ReportCrashIfDebug("Hit MOZ_CRASH(Tried to access a protected region!)\n");
                MOZ_CRASH_ANNOTATE("MOZ_CRASH(Tried to access a protected region!)");
            }
        }
    }

    // Forward to the previous handler which may be a debugger,
    // the crash reporter or something else entirely.
    if (sPrevSEGVHandler.sa_flags & SA_SIGINFO)
        sPrevSEGVHandler.sa_sigaction(signum, info, context);
    else if (sPrevSEGVHandler.sa_handler == SIG_DFL || sPrevSEGVHandler.sa_handler == SIG_IGN)
        sigaction(SIGSEGV, &sPrevSEGVHandler, nullptr);
    else
        sPrevSEGVHandler.sa_handler(signum);

    // If we reach here, we're returning to let the default signal handler deal
    // with the exception. This is technically undefined behavior, but
    // everything seems to do it, and it removes us from the crash stack.
}

 AutoWalkJSStack() : walkAllowed(false) {
   walkAllowed = WALKING_JS_STACK.compareExchange(false, true);
 }