--- gcc/config/xm-aix386.h	2018/04/24 17:51:34	1.1
+++ gcc/config/xm-aix386.h	2018/04/24 18:05:01	1.1.1.2
@@ -49,6 +49,10 @@ the Free Software Foundation, 675 Mass A
 #define bzero(a,b) memset (a,0,b)
 #define bcmp(a,b,c) memcmp (a,b,c)
 
+/* If compiled with GNU C, use the built-in alloca.  */
+#undef alloca
 #ifdef __GNUC__
-#define alloca(n) __builtin_alloca(n)
+#define alloca __builtin_alloca
+#else
+#define USE_C_ALLOCA
 #endif