diff --git a/llvm/lib/Support/Unix/Process.inc b/llvm/lib/Support/Unix/Process.inc
--- a/llvm/lib/Support/Unix/Process.inc
+++ b/llvm/lib/Support/Unix/Process.inc
@@ -236,11 +236,11 @@
 
 std::error_code Process::SafelyCloseFileDescriptor(int FD) {
   // Create a signal set filled with *all* signals.
-  sigset_t FullSet;
-  if (sigfillset(&FullSet) < 0)
+  sigset_t FullSet, SavedSet;
+  if (sigfillset(&FullSet) < 0 || sigfillset(&SavedSet) < 0)
     return std::error_code(errno, std::generic_category());
+
   // Atomically swap our current signal mask with a full mask.
-  sigset_t SavedSet;
 #if LLVM_ENABLE_THREADS
   if (int EC = pthread_sigmask(SIG_SETMASK, &FullSet, &SavedSet))
     return std::error_code(EC, std::generic_category());