we don't have an alloca() symbol anywhere in libc, don't prototype it.

instead, #define to __builtin_alloca. if that doesn't work, you're hosed.
from an old discussion about the perils of alloca. (don't use alloca!)

diff --git a/include/stdlib.h b/include/stdlib.h
index d048e70..fd2fc27 100644 (file)
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: stdlib.h,v 1.62 2014/12/08 21:45:19 deraadt Exp $     */
+/*     $OpenBSD: stdlib.h,v 1.63 2015/01/15 19:55:58 tedu Exp $        */
 /*     $NetBSD: stdlib.h,v 1.25 1995/12/27 21:19:08 jtc Exp $  */
 
 /*-
@@ -267,7 +267,7 @@ int mkostemp(char *, int);
 #endif
 
 #if __BSD_VISIBLE
-void   *alloca(size_t); 
+#define alloca(n) __builtin_alloca(n)
 
 char   *getbsize(int *, long *);
 char   *cgetcap(char *, const char *, int);