[Tsan] Adjust SA_SIGINFO and SIG_SETMASK values on FreeBSD.

[samsonov]

LGTM

[dvyukov]

LGTM

lib/tsan/rtl/tsan_interceptors.cc

 #endif
   void (*sa_restorer)();
 #endif
 };
 
 const sighandler_t SIG_DFL = (sighandler_t)0;
 const sighandler_t SIG_IGN = (sighandler_t)1;
 const sighandler_t SIG_ERR = (sighandler_t)-1;
-#ifdef __mips__
+#if SANITIZER_FREEBSD
+const int SA_SIGINFO = 0x40;
+const int SIG_SETMASK = 3;
+#elif defined(__mips__)
 const int SA_SIGINFO = 8;
 const int SIG_SETMASK = 3;
 #else
 const int SA_SIGINFO = 4;
 const int SIG_SETMASK = 2;
 #endif
 
 namespace std {
void ProcessPendingSignals(ThreadState *thr) {
   ThreadSignalContext *sctx = SigCtx(thr);
   if (sctx == 0 ||
       atomic_load(&sctx->have_pending_signals, memory_order_relaxed) == 0)
     return;
   atomic_store(&sctx->have_pending_signals, 0, memory_order_relaxed);
   atomic_fetch_add(&thr->in_signal_handler, 1, memory_order_relaxed);
   // These are too big for stack.
   static THREADLOCAL __sanitizer_sigset_t emptyset, oldset;
-  REAL(sigfillset)(&emptyset);
-  pthread_sigmask(SIG_SETMASK, &emptyset, &oldset);
+  CHECK_EQ(0, REAL(sigfillset)(&emptyset));
+  CHECK_EQ(0, pthread_sigmask(SIG_SETMASK, &emptyset, &oldset));
   for (int sig = 0; sig < kSigCount; sig++) {
     SignalDesc *signal = &sctx->pending_signals[sig];
     if (signal->armed) {
       signal->armed = false;
       CallUserSignalHandler(thr, false, true, signal->sigaction, sig,
           &signal->siginfo, &signal->ctx);
     }
   }
-  pthread_sigmask(SIG_SETMASK, &oldset, 0);
+  CHECK_EQ(0, pthread_sigmask(SIG_SETMASK, &oldset, 0));
   atomic_fetch_add(&thr->in_signal_handler, -1, memory_order_relaxed);
 }
 
 }  // namespace __tsan
 
 static bool is_sync_signal(ThreadSignalContext *sctx, int sig) {
   return sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
       sig == SIGABRT || sig == SIGFPE || sig == SIGPIPE || sig == SIGSYS ||