[Boost-users] Re: [Foreach] Trouble iterating over Boost.MultiIndexcontainers

From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2005-03-02 15:40:18

"Eric Niebler" <eric_at_[hidden]> wrote in message
news:4226204E.4020105_at_boost-consulting.com...
>
> Eelis van der Weegen wrote:
> > I'm having trouble using BOOST_FOREACH to iterate over Boost.MultiIndex
> > containers. I've attached a testcase, which fails to compile because of
> > what looks like an ADL collision between range_iterator's end() and
> > boost::mpl::end.
> >
> > I'm using GCC 3.4.2 with foreach.hpp revision 1.22 from the sandbox.
> > Others have reported that GCC 4.0.0 20050130 is also affected.
> >
> > (I'm aware that BOOST_FOREACH isn't part of Boost yet, but it's in the
> > review queue so I thought posting this here was appropriate.)
> >
>
>
> I can reproduce the problem with gcc 3.3.3 (cygwin), but the problem
> does not reproduce with Visual C++. I'm a bit at a loss here. There is
> really no problem with BOOST_FOREACH or with its use of Boost.Range or
> with Boost.MPL that I can see. It would seem to be a compiler problem. I
> don't know why ADL is finding a class name, and I'm not sure what a
> suitable work-around should be. I'll give it some thought.
>
> Actually, I seem to recall reading about this problem (there might even
> be a defect report already). If anybody can refresh my memory, I'd
> appreciate it.

It appears to be the same problem that I ran into a few month ago...

This is a combination of two problems with GCC:

1) GCC STL uses unqualified function calls to its own functions, such as
end() in this particular case;
2) GCC ADL finds class names along with function names.

So, if an STL algorithm is used with a sequence whose value_type has
anything related to boost::mpl namespace, and this algorithm uses
unqualified call, and the appropriate MPL header is included, then the
problem shows up.

I think GCC people are fixing number 1 (which will make the problem go
away), but I don't know if they are done yet (apparently not).

Regards,
Arkadiy