From: Vincent Pit <perl@profvince.com>
Date: Wed, 31 Mar 2010 12:33:32 +0000 (+0200)
Subject: Don't initialize end in pp_reverse when begin is NULL
X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=commitdiff_plain;h=95a26d8e5a73b4fe66d7b066732f59cd675632d0;p=p5sagit%2Fp5-mst-13.2.git

Don't initialize end in pp_reverse when begin is NULL

This change is a complement to 572558b47236782e60e41bd235c96eae7cbca3db.

Arithmetic on null pointers isn't defined by the C standard, so it may crash even before entering the loop.
---

diff --git a/pp.c b/pp.c
index daa63af..e4660b3 100644
--- a/pp.c
+++ b/pp.c
@@ -5418,12 +5418,15 @@ PP(pp_reverse)
 	    }
 	    else {
 		SV **begin = AvARRAY(av);
-		SV **end   = begin + AvFILLp(av);
 
-		while (begin && begin < end) {
-		    register SV * const tmp = *begin;
-		    *begin++ = *end;
-		    *end--   = tmp;
+		if (begin) {
+		    SV **end   = begin + AvFILLp(av);
+
+		    while (begin < end) {
+			register SV * const tmp = *begin;
+			*begin++ = *end;
+			*end--   = tmp;
+		    }
 		}
 	    }
 	}