Re: CAtlRegExp bug/crash

From:

Ismo Salonen <Ismo.Salonen@codeit.fi>

Newsgroups:

microsoft.public.vc.atl,microsoft.public.msdn.general

Date:

Mon, 04 Sep 2006 09:36:06 +0300

Message-ID:

<epHrjx#zGHA.3908@TK2MSFTNGP05.phx.gbl>

David Lowndes wrote:

One of our user discovered that using regular expression to match empty
input gives unpredictable results. E.g matching expression .+ agains
empty string produces true. In my opinion it shoild evaluate as false.

After more testing I discovered that matching empty string with
expression \a+ crashes inside CAtlRegExp.Match(), in my version on line
638 in atlrx.h. The actual crash happens one line before, at size_t u =
(size_t) *sz; The sz has been incremented beyond end of string.

Can anybody confirm my findings and/or has this been fixed to some
version ?

Have you got a short code example that neatly demonstrates the problem
you're having?

Dave

Here is example which crashes every time. Just compile and run,
Multithreaded debug dll was my selection for code generation.
Stdafx is here

-----------------
#pragma once

#include <iostream>
#include <tchar.h>

------
and it is easily removed . Tailor the code compile.

-------------------------------------

// regbug.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <string>
#include <atlrx.h>

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{

    CAtlRegExp<> re;
    CAtlREMatchContext<> mc;
    string what("");
    string rest("\\a+");
    string result;

    REParseError status = re.Parse(rest.c_str());

    if (REPARSE_ERROR_OK != status)
    {
        cout << " Parse error " << status << endl;
        return false;
    }

    if( re.Match( what.c_str() , &mc ) )
    {
        result = "1";
    }
    else
    {
        result = "0";
    }
    cout << "result is " << result << endl;
    return 0;
}

// ismo