--- Libc/Libc-1669.40.2/include/alloca.h
+++ Libc/Libc-583/include/alloca.h
@@ -26,13 +26,15 @@
 
 #include <sys/cdefs.h>
 #include <_types.h>
-#include <sys/_types/_size_t.h>
 
-#ifndef UNIFDEF_DRIVERKIT
+#ifndef	_SIZE_T
+#define	_SIZE_T
+typedef	__darwin_size_t	size_t;
+#endif
+
 __BEGIN_DECLS
 void	*alloca(size_t);		/* built-in for gcc */
 __END_DECLS
-#endif /* UNIFDEF_DRIVERKIT */
 
 #if defined(__GNUC__) && __GNUC__ >= 3
 /* built-in for gcc 3 */