(NULL): Define only if not already defined.

diff --git a/alloca.c b/alloca.c
index 12c1122981cbc5c76ef1432ae04bceacba1e1fa2..31fb4e0d4e0685a0f34c3ce994f33e64591d2d50 100644 (file)
--- a/alloca.c
+++ b/alloca.c
@@ -73,7 +73,9 @@ typedef void *pointer;
 typedef char *pointer;
 #endif
 
+#ifndef NULL
 #define        NULL    0
+#endif
 
 /* Different portions of Emacs need to call different versions of
    malloc.  The Emacs executable needs alloca to call xmalloc, because