diff --git a/clang/lib/Headers/stdarg.h b/clang/lib/Headers/stdarg.h
--- a/clang/lib/Headers/stdarg.h
+++ b/clang/lib/Headers/stdarg.h
@@ -8,7 +8,17 @@
  */
 
 #ifndef __STDARG_H
+#ifndef __need___va_list
 #define __STDARG_H
+#endif /* __need___va_list */
+#undef __need___va_list
+
+#ifndef __GNUC_VA_LIST
+#define __GNUC_VA_LIST 1
+typedef __builtin_va_list __gnuc_va_list;
+#endif
+
+#ifdef __STDARG_H
 
 #ifndef _VA_LIST
 typedef __builtin_va_list va_list;
@@ -29,9 +39,6 @@
 #define va_copy(dest, src)  __builtin_va_copy(dest, src)
 #endif
 
-#ifndef __GNUC_VA_LIST
-#define __GNUC_VA_LIST 1
-typedef __builtin_va_list __gnuc_va_list;
-#endif
-
 #endif /* __STDARG_H */
+
+#endif /* not __STDARG_H */
diff --git a/compiler-rt/test/sanitizer_common/TestCases/Linux/signal_send.cpp b/compiler-rt/test/sanitizer_common/TestCases/Linux/signal_send.cpp
--- a/compiler-rt/test/sanitizer_common/TestCases/Linux/signal_send.cpp
+++ b/compiler-rt/test/sanitizer_common/TestCases/Linux/signal_send.cpp
@@ -5,6 +5,7 @@
 
 #include <assert.h>
 #include <signal.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <sys/time.h>
 #include <sys/wait.h>