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Re: Stack overflow in regexp matcher


From: Ilya Zakharevich
Subject: Re: Stack overflow in regexp matcher
Date: Thu, 17 Dec 2009 22:10:55 +0000 (UTC)
User-agent: slrn/0.9.8.1pl1 (Linux)

On 2009-12-17, Barry Margolin <address@hidden> wrote:
>> A function of mine gets "Stack overflow in regexp matcher" on a certain 
>> file using the regexp
>> 
>>      "^< \\(.+].+=|\\)"

> The problem is that + is greedy, so this has to scan the entire line 
> looking for the last "]", then see if there's an "=" somewhere later.  
> If it can't find an "=" it has to back up to the previous "]" and search 
> again, and so on.  If there are lots of "]" characters, this has to save 
> the state of each of them in the matching stack.

What for?  There is no need to keep state of unsuccessful matches...

So the "next-]" state should replace the older one.

Yours,
Ilya


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