[Bug c++/23213] New: Error in Koenig Lookup causes overload resolution failure

[Bug c++/23213] New: Error in Koenig Lookup causes overload resolution failure

[adah at netstd dot com]

http://groups-beta.google.com/group/comp.lang.c++.moderated/browse_thread/thread/3c449572456c8592

The test program:

#include <vector>
int distance(std::vector<int> v1, std::vector<int> v2)
{
    return v1.size() - v2.size();
}
int main()
{
    std::vector<int> v1(3), v2(1);
    int d = distance(v1, v2);
    return 0;
}

The error message from 3.4.4:

D:/mingw-gcc3.4/bin/../lib/gcc/mingw32/3.4.4/../../../../include/c++/3.4.4/bits/stl_iterator_base_types.h:
In instantiation of `std::iterator_traits<std::vector<int, std::allocator<int> > >':
test1.cpp:11:   instantiated from here
D:/mingw-gcc3.4/bin/../lib/gcc/mingw32/3.4.4/../../../../include/c++/3.4.4/bits/stl_iterator_base_types.h:129:
error: no type named `iterator_category' in `class std::vector<int,
std::allocator<int> >'

It has been confirmed that the problem is not that Koenig lookup takes priority
over the local overload, etc.  It is that the failure to deduce the return type
of the instantiation of std::distance<>() caused the abortion of candidate
building.  If the necessary typedef is provided, the local version of distance
will be correctly selected.

It might be arguable whether SFINAE should be applied here (the C++ standard is
not quite clear on this).  But I do not think it the purpose of the standard to
let something in the std namespace affect local name resolution.  Maybe you
gurus here can judge better?

This problem occurs from 2.95.3 to 3.4.4.  I believe it is platform-independent.

-- 
           Summary: Error in Koenig Lookup causes overload resolution
                    failure
           Product: gcc
           Version: 3.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: adah at netstd dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-pc-mingw32
  GCC host triplet: i386-pc-mingw32
GCC target triplet: i386-pc-mingw32


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23213

[Bug c++/23213] Error in Koenig Lookup causes overload resolution failure

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-03 12:56 -------


*** This bug has been marked as a duplicate of 15910 ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23213

[Bug c++/23213] Error in Koenig Lookup causes overload resolution failure

[gdr at integrable-solutions dot net]

------- Additional Comments From gdr at integrable-solutions dot net  2005-08-04 10:02 -------
Subject: Re:  New: Error in Koenig Lookup causes overload resolution failure

"adah at netstd dot com" <gcc-bugzilla@gcc.gnu.org> writes:

| http://groups-beta.google.com/group/comp.lang.c++.moderated/browse_thread/thread/3c449572456c8592

[...]

| not quite clear on this).  But I do not think it the purpose of the standard to
| let something in the std namespace affect local name resolution.  Maybe you
| gurus here can judge better?

Whether you like it or not, you have to take it to the C++ committee.
It is not GCC's job to "fix" C++ standard semantics you would not
like.

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23213