[Boost-users] Weird regex compiler warnings with VC 7.1

From: Alan Davies (cs96and_at_[hidden])
Date: 2006-01-25 07:43:04

Hello.

I've come across a weird compiler warning when using the regex library on VC
7.1 (I think the problem also occurs in VC 7.0).  I'm using Boost 1.33.1

The code below throws up warnings.  Removing the min() call from main, or
changing a, b and c's type to anything else (e.g. short) gets rid of the
warnings.

The offending line is in regex_format.hpp (it appears twice in that file):

std::ptrdiff_t len = (std::min)(static_cast<std::ptrdiff_t>(2),
::boost::re_detail::distance(m_position, m_end));

Putting a static cast around the distance() call makes no difference, but
splitting it into two lines as follows gets rid of the warning:

std::ptrdiff_t distance = ::boost::re_detail::distance(m_position, m_end);
std::ptrdiff_t len = (std::min)(static_cast<std::ptrdiff_t>(2), distance);

This makes absolutely no sense to me!

My code and the warnings are below.

#include "boost/regex.hpp"
#include <iostream>
#include <string>

int main(int argc, char *argv[])
{
    std::string hello = "hello    world!";
    boost::regex multipleSpacesRegex("([[:space:]]){2,}");

    int a=1, b=2;
    // Remove the next line to get rid of the warnings
    int c=(std::min)(a,b);

    hello = boost::regex_replace(hello, multipleSpacesRegex, "$1");

    std::cout << hello << std::endl;
    return 0;
}

------ Build started: Project: regex_test, Configuration: Debug Win32 ------

Compiling...
main.cpp
f:\dev\include\boost\regex\v4\regex_format.hpp(246) : warning C4244: 'argument'
: conversion from 'std::iterator_traits<_Iter>::difference_type' to 'const
int', possible loss of data
        with
        [
            _Iter=const char *
        ]
        f:\dev\include\boost\regex\v4\sub_match.hpp(130) : while compiling
class-template member function 'void
boost::re_detail::basic_regex_formatter<OutputIterator,Results,traits>::format_perl(void)'
        with
        [
           
OutputIterator=boost::re_detail::string_out_iterator<std::basic_string<char,std::char_traits<char>,std::allocator<char>>>,
           
Results=boost::match_results<std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator>,
            traits=boost::regex_traits_wrapper<boost::regex_traits<char>>
        ]
        c:\Program Files\Microsoft Visual Studio .NET
2003\Vc7\include\vector(152) : while compiling class-template member function
'void
boost::re_detail::basic_regex_formatter<OutputIterator,Results,traits>::format_all(void)'
        with
        [
           
OutputIterator=boost::re_detail::string_out_iterator<std::basic_string<char,std::char_traits<char>,std::allocator<char>>>,
           
Results=boost::match_results<std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator>,
            traits=boost::regex_traits_wrapper<boost::regex_traits<char>>
        ]
        c:\Program Files\Microsoft Visual Studio .NET
2003\Vc7\include\xstring(542) : while compiling class-template member function
'boost::re_detail::string_out_iterator<S>
boost::re_detail::basic_regex_formatter<OutputIterator,Results,traits>::format(const
boost::re_detail::basic_regex_formatter<OutputIterator,Results,traits>::char_type
*,const
boost::re_detail::basic_regex_formatter<OutputIterator,Results,traits>::char_type
*,boost::regex_constants::match_flag_type)'
        with
        [
           
S=std::basic_string<char,std::char_traits<char>,std::allocator<char>>,
           
OutputIterator=boost::re_detail::string_out_iterator<std::basic_string<char,std::char_traits<char>,std::allocator<char>>>,
           
Results=boost::match_results<std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator>,
            traits=boost::regex_traits_wrapper<boost::regex_traits<char>>
        ]
        f:\dev\include\boost\regex\v4\regex_format.hpp(568) : see reference to
class template instantiation
'boost::re_detail::basic_regex_formatter<OutputIterator,Results,traits>' being
compiled
        with
        [
           
OutputIterator=boost::re_detail::string_out_iterator<std::basic_string<char,std::char_traits<char>,std::allocator<char>>>,
           
Results=boost::match_results<std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator>,
            traits=boost::regex_traits_wrapper<boost::regex_traits<char>>
        ]
        f:\dev\include\boost\regex\v4\match_results.hpp(170) : see reference to
function template instantiation 'OutputIterator
boost::re_detail::regex_format_imp<OutputIterator,std::basic_string<_Elem,_Traits,_Ax>::const_iterator,std::vector<_Ty>::allocator_type,_Elem,boost::regex_traits_wrapper<BaseT>>(OutputIterator,const
boost::match_results<BidiIterator> &,const charT *,const charT
*,boost::regex_constants::match_flag_type,const traits &)' being compiled
        with
        [
           
OutputIterator=boost::re_detail::string_out_iterator<std::basic_string<char,std::char_traits<char>,std::allocator<char>>>,
            _Elem=char,
            _Traits=std::char_traits<char>,
            _Ax=std::allocator<char>,
           
_Ty=boost::sub_match<std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator>,
            BaseT=boost::regex_traits<char>,
           
BidiIterator=std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator,
            charT=char,
            traits=boost::regex_traits_wrapper<boost::regex_traits<char>>
        ]
        f:\dev\include\boost\regex\v4\regex_replace.hpp(53) : see reference to
function template instantiation 'OutputIterator
boost::match_results<BidiIterator>::format<OutputIterator,boost::basic_regex<charT,traits>>(OutputIterator,const
boost::match_results<BidiIterator>::st		 std::ptrdiff_t distance =
::boost::re_detail::distance(m_position, m_end);
         std::ptrdiff_t len = (std::min)(static_cast<std::ptrdiff_t>(2),
distance);
ring_type &,boost::regex_constants::match_flag_type,const RegexT &) const'
being compiled
        with
        [
           
OutputIterator=boost::re_detail::string_out_iterator<std::basic_string<char,std::char_traits<char>,std::allocator<char>>>,
           
BidiIterator=std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator,
            charT=char,
            traits=boost::regex_traits<char>,
            RegexT=boost::basic_regex<char,boost::regex_traits<char>>
        ]
        f:\dev\include\boost\regex\v4\regex_replace.hpp(84) : see reference to
function template instantiation 'OutputIterator
boost::regex_replace<boost::re_detail::string_out_iterator<S>,std::basic_string<_Elem,_Traits,_Ax>::const_iterator,boost::regex_traits<charT>,char>(OutputIterator,BidirectionalIterator,BidirectionalIterator,const
boost::basic_regex<charT,traits> &,const charT
*,boost::regex_constants::match_flag_type)' being compiled
        with
        [
           
OutputIterator=boost::re_detail::string_out_iterator<std::basic_string<char,std::char_traits<char>,std::allocator<char>>>,
           
S=std::basic_string<char,std::char_traits<char>,std::allocator<char>>,
            _Elem=char,
            _Traits=std::char_traits<char>,
            _Ax=std::allocator<char>,
            charT=char,
           
BidirectionalIterator=std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator,
            traits=boost::regex_traits<char>
        ]
        f:\dev\projects\regex_test\main.cpp(17) : see reference to function
template instantiation 'std::basic_string<_Elem,_Traits,_Ax>
boost::regex_replace<boost::regex_traits<charT>,char>(const
std::basic_string<_Elem,_Traits,_Ax> &,const boost::basic_regex<charT,traits>
&,const charT *,boost::regex_constants::match_flag_type)' being compiled
        with
        [
            _Elem=char,
            _Traits=std::char_traits<char>,
            _Ax=std::allocator<char>,
            charT=char,
            traits=boost::regex_traits<char>
        ]
f:\dev\include\boost\regex\v4\regex_format.hpp(330) : warning C4244: 'argument'
: conversion from 'std::iterator_traits<_Iter>::difference_type' to 'const
int', possible loss of data
        with
        [
            _Iter=const char *
        ]
        f:\dev\include\boost\regex\v4\sub_match.hpp(130) : while compiling
class-template member function 'void
boost::re_detail::basic_regex_formatter<OutputIterator,Results,traits>::format_escape(void)'
        with
        [
           
OutputIterator=boost::re_detail::string_out_iterator<std::basic_string<char,std::char_traits<char>,std::allocator<char>>>,
           
Results=boost::match_results<std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator>,
            traits=boost::regex_traits_wrapper<boost::regex_traits<char>>
        ]
f:\dev\include\boost\regex\v4\regex_format.hpp(401) : warning C4244: 'argument'
: conversion from 'std::iterator_traits<_Iter>::difference_type' to 'const
int', possible loss of data
        with
        [
            _Iter=const char *
        ]
f:\dev\include\boost\regex\v4\regex_format.hpp(422) : warning C4244: 'argument'
: conversion from 'std::iterator_traits<_Iter>::difference_type' to 'const
int', possible loss of data
        with
        [
            _Iter=const char *
        ]
        f:\dev\include\boost\regex\v4\sub_match.hpp(130) : while compiling
class-template member function 'void
boost::re_detail::basic_regex_formatter<OutputIterator,Results,traits>::format_conditional(void)'
        with
        [
           
OutputIterator=boost::re_detail::string_out_iterator<std::basic_string<char,std::char_traits<char>,std::allocator<char>>>,
           
Results=boost::match_results<std::basic_string<char,std::char_traits<char>,std::allocator<char>>::const_iterator>,
            traits=boost::regex_traits_wrapper<boost::regex_traits<char>>
        ]
Linking...

Build log was saved at "file://f:\dev\projects\regex_test\Debug\BuildLog.htm"
regex_test - 0 error(s), 4 warning(s)

---------------------- Done ----------------------

    Build: 1 succeeded, 0 failed, 0 skipped

                
___________________________________________________________ 
Yahoo! Photos – NEW, now offering a quality print service from just 8p a photo http://uk.photos.yahoo.com