Re: [Boost-users] boost::format with empty string...

From: Early Ehlinger (early_at_[hidden])
Date: 2007-03-29 12:27:47

I should've mentioned that.  Yes - 1.33.1.

-- Early

Shams wrote:
> Hi,
> 
> I assume you're using the current official release.
> I believe the problem is already fixed in 1.34 in CVS.
> 
> Thanks
> Shams
> 
> ----- Original Message ----- 
> From: "Early Ehlinger" <early_at_[hidden]>
> Newsgroups: gmane.comp.lib.boost.user
> To: <boost-users_at_[hidden]>
> Sent: Thursday, March 29, 2007 4:46 AM
> Subject: boost::format with empty string...
> 
> 
>> Using MS Visual C++ 2005, Express Edition, the following snippet causes an 
>> assertion failure due to a NULL pointer in the bowels of boost::format:
>>
>>  boost::format f( "test %1%\n" );
>>  f % "";
>>
>> I traced it down to boost/format/feed_args.hpp:
>>
>>    template<class Ch, class Tr, class Alloc>
>>    void mk_str( std::basic_string<Ch,Tr, Alloc> & res,
>>                 const Ch * beg,
>>                 typename std::basic_string<Ch,Tr,Alloc>::size_type size,
>>                 std::streamsize w,
>>                 const Ch fill_char,
>>                 std::ios_base::fmtflags f,
>>                 const Ch prefix_space, // 0 if no space-padding
>>                 bool center)
>>    // applies centered/left/right  padding  to the string  [beg, beg+size[
>>    // Effects : the result is placed in res.
>>    {
>>        typedef typename std::basic_string<Ch,Tr,Alloc>::size_type 
>> size_type;
>>        res.resize(0);
>>        if( ( w<=0 || static_cast<size_type>(w) <=size)) {
>>            // no need to pad.
>>            res.reserve(size + !!prefix_space);
>>            if(prefix_space)
>>              res.append(1, prefix_space);
>>            res.append(beg, size); <<--- crashes, because beg==NULL and 
>> size==0
>> ...
>> My suggested fix looks like this:
>>    template<class Ch, class Tr, class Alloc>
>>    void mk_str( std::basic_string<Ch,Tr, Alloc> & res,
>>                 const Ch * beg,
>>                 typename std::basic_string<Ch,Tr,Alloc>::size_type size,
>>                 std::streamsize w,
>>                 const Ch fill_char,
>>                 std::ios_base::fmtflags f,
>>                 const Ch prefix_space, // 0 if no space-padding
>>                 bool center)
>>    // applies centered/left/right  padding  to the string  [beg, beg+size[
>>    // Effects : the result is placed in res.
>>    {
>>        typedef typename std::basic_string<Ch,Tr,Alloc>::size_type 
>> size_type;
>>        res.resize(0);
>>        if(size && ( w<=0 || static_cast<size_type>(w) <=size)) {
>>            // no need to pad.
>>            res.reserve(size + !!prefix_space);
>>            if(prefix_space)
>>              res.append(1, prefix_space);
>>            res.append(beg, size);
>>        }
>>        else {
>>            std::streamsize 
>> n=static_cast<std::streamsize>(w-size-!!prefix_space);
>>            std::streamsize n_after = 0, n_before = 0;
>>            res.reserve(w); // allocate once for the 2 inserts
>>            if(center)
>>                n_after = n/2, n_before = n - n_after;
>>            else
>>                if(f & std::ios_base::left)
>>                    n_after = n;
>>                else
>>                    n_before = n;
>>            // now make the res string :
>>            if(n_before) res.append(n_before, fill_char);
>>            if(prefix_space)
>>              res.append(1, prefix_space);
>>            if ( size )
>>              res.append(beg, size);
>>            if(n_after) res.append(n_after, fill_char);
>>        }
>>    } // -mk_str(..)
>>
>> -- Early Ehlinger, President, ResPower, Inc.