Re: [perl #75258] regex match fails for long input (> 32768? chars)

On Sat, May 22, 2010 at 01:24:10AM -0700, Terada Minoru wrote:
> # New Ticket Created by  Terada Minoru 
> # Please include the string:  [perl #75258]
> # in the subject line of all future correspondence about this issue. 
> # <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=75258 >
> 
> 
> 
> To: [email protected]
> Subject: regex match fails for long input (> 32768? chars)
> Reply-To: [email protected]
> Message-Id: <[email protected]>
> 
> This is a bug report for perl from [email protected],
> generated with the help of perlbug 1.35 running under perl v5.8.8.
> 
> 
> -----------------------------------------------------------------
> [Please enter your report here]
> 
> Here is a test case:
> ========
> #! /usr/bin/perl
> 
> $n = 32768;
> 
> $str = "{";
> for($i=0; $i<$n; $i++){
>     $str = $str . "X";
> }
> $str = $str . "}";
> 
> if($str =~ /^{((E.|[^}E])*)}/){
>     print "$2\n";
> } else {
>     print "MATCH FAILED\n";
> }
> 
> 1;
> ========
> I tried perl 5.8.8 and 5.13.1.
> 
> If $n <= 32767, the result is correct for both versions.
> (The match succeeds.)
> 
> For larger $n (>= 32768), the bug appears:
>   On 5.8.8, Segmentation fault occurs.
>   On 5.13.1, the match fails.
> 

Thank you for your report.

This is a known bug. Patterns of the form /(A|B)*/ are really
/(A|B){0,32767}/. One might argue that not giving a segfault is
an improvement, but I'm not so sure if silently giving the wrong
answer is better.


$ perl -Mre=debug -wce '/(A|B)*/'
Compiling REx "(A|B)*"
Final program:
   1: CURLYM[1] {0,32767} (15)
   5:   TRIE-EXACT[AB] (13)
        <A> 
        <B> 
  13:   SUCCEED (0)
  14: NOTHING (15)
  15: END (0)
minlen 0 
-e syntax OK
Freeing REx: "(A|B)*"
$


Abigail