tsan: move errno spoiling reporting into a separate function (NFC)

[dvyukov]

Summary

CallUserSignalHandler function is quite large and complex.
Move errno spoiling reporting into a separate function.
No logical changes.

compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp

 TSAN_INTERCEPTOR(int, pthread_sigmask, int how, const __sanitizer_sigset_t *set,
     __sanitizer_sigset_t *oldset) {
   SCOPED_TSAN_INTERCEPTOR(pthread_sigmask, how, set, oldset);
   return REAL(pthread_sigmask)(how, set, oldset);
 }
 
 namespace __tsan {
 
+static void ReportErrnoSpoiling(ThreadState *thr, uptr pc) {
+  VarSizeStackTrace stack;
+  // StackTrace::GetNestInstructionPc(pc) is used because return address is
+  // expected, OutputReport() will undo this.
+  ObtainCurrentStack(thr, StackTrace::GetNextInstructionPc(pc), &stack);
+  ThreadRegistryLock l(&ctx->thread_registry);
+  ScopedReport rep(ReportTypeErrnoInSignal);
+  if (!IsFiredSuppression(ctx, ReportTypeErrnoInSignal, stack)) {
+    rep.AddStack(stack, true);
+    OutputReport(thr, rep);
+  }
+}
+
 static void CallUserSignalHandler(ThreadState *thr, bool sync, bool acquire,
                                   int sig, __sanitizer_siginfo *info,
                                   void *uctx) {
   __sanitizer_sigaction *sigactions = interceptor_ctx()->sigactions;
   if (acquire)
     Acquire(thr, 0, (uptr)&sigactions[sig]);
   // Signals are generally asynchronous, so if we receive a signals when
   // ignores are enabled we should disable ignores. This is critical for sync
static void CallUserSignalHandler(ThreadState *thr, bool sync, bool acquire,
   // We do not detect errno spoiling for SIGTERM,
   // because some SIGTERM handlers do spoil errno but reraise SIGTERM,
   // tsan reports false positive in such case.
   // It's difficult to properly detect this situation (reraise),
   // because in async signal processing case (when handler is called directly
   // from rtl_generic_sighandler) we have not yet received the reraised
   // signal; and it looks too fragile to intercept all ways to reraise a signal.
   if (ShouldReport(thr, ReportTypeErrnoInSignal) && !sync && sig != SIGTERM &&
-      errno != 99) {
-    VarSizeStackTrace stack;
-    // StackTrace::GetNestInstructionPc(pc) is used because return address is
-    // expected, OutputReport() will undo this.
-    ObtainCurrentStack(thr, StackTrace::GetNextInstructionPc(pc), &stack);
-    ThreadRegistryLock l(&ctx->thread_registry);
-    ScopedReport rep(ReportTypeErrnoInSignal);
-    if (!IsFiredSuppression(ctx, ReportTypeErrnoInSignal, stack)) {
-      rep.AddStack(stack, true);
-      OutputReport(thr, rep);
-    }
-  }
+      errno != 99)
+    ReportErrnoSpoiling(thr, pc);
   errno = saved_errno;
 }
 
 void ProcessPendingSignalsImpl(ThreadState *thr) {
   atomic_store(&thr->pending_signals, 0, memory_order_relaxed);
   ThreadSignalContext *sctx = SigCtx(thr);
   if (sctx == 0)
     return;