Die on patterns that will match empty string forever

Subject: Re: Segementation fault in perl5.001 and 5.003 

Strange sunspot activity caused =?iso-8859-1?Q?Markus_Thei=DFinger?= <Markus.Th
eissinger@gmd.de> to write:
| Hi,
| 
| perl -e '$_=3D" 2"; print STDOUT /^(\s*(\))*)+$/;'
| 
| produces a segmentation fault [snips]

Confirmed on 3_95.  I'm surprised this kind of thing lasted this long.
Actually, I could have sworn someone fixed this awhile back.  I suppose one
of the regulars could probably provide a better patch.

Works fine on 4.036, this patch returns it to 4.036 functionality.

p5p-msgid: 199703282138.PAA28311@psa.pencom.com

1 files changed, 4 insertions, 0 deletions

diff --git a/regcomp.c b/regcomp.c
index 4c34b59c61..5dad7d78e2 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -697,6 +697,10 @@ I32 *flagp;
 	*flagp = flags;
 	return(ret);
     }
+
+    if (!(flags&HASWIDTH) && op != '?')
+      FAIL("regexp *+ operand could be empty");
+
     nextchar();
 
     *flagp = (op != '+') ? (WORST|SPSTART) : (WORST|HASWIDTH);