Re: [Boost-users] Corrupted boost::regex::smatch results (on MSVS2003)

Subject: Re: [Boost-users] Corrupted boost::regex::smatch results (on MSVS2003)
From: david.weber_at_[hidden]
Date: 2009-04-14 12:44:19

That's exactly what was happening.  I pondered over what you wrote for
about 24 hours, and it just "clicked" while brushing my teeth.  I
suppose the part that clicked, was the unspoken bit.  I.E.: the
match_results object is tied directly to the string you are operating
on.

We had something like:

Boost::regex::smatch matchString(std::string str)
{
        boost::regex::smatch retValue;

        // assign retValue by using boost::regex
        // doesn't work, and I don't care to look up syntax :)
        // retValue = regex.match(str);

        return retValue;
}

I didn't realize that the smatch required the string to remain in scope
for it to be considered valid.  I just checked the documentation
quickly, and I actually didn't see this mentioned *anywhere*.  Was I
blind, and just missed it?

Anyway, passing str as a const reference solved the problem, and we're
happy again.  My guess is that windows was invalidating the memory as
soon as str went out of scope, rendering the data "bad".  Opposed to our
Linux build, where the data was still in memory (invalid, but still
present), so we were able to still limp along.

Yay for multi-platforms and boost::test :)

Thanks for the inspiration/fix

--dw

-----Original Message-----
From: boost-users-bounces_at_[hidden]
[mailto:boost-users-bounces_at_[hidden]] On Behalf Of John Maddock
Sent: Saturday, April 11, 2009 3:37 AM
To: boost-users_at_[hidden]
Subject: Re: [Boost-users] Corrupted boost::regex::smatch results (on
MSVS2003)

>I'm using Boost.Regex from v1.35.0.  We're seeing the smatch 
>matchresults object getting corrupted when being returned by value from

>a function.  The smatch variable is good within the function (it is an 
>object defined locally on the stack), but when returned it is corrupted

>with bad data.

What do you mean by bad data?

Is it simply that the iterators have been invalidated because the string
that was matched no longer exists?

HTH, John. 

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