[Bug c++/50399] New: [c++11] Lookup error w/ enums

[Bug c++/50399] New: [c++11] Lookup error w/ enums

[blelbach at cct dot lsu.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50399

             Bug #: 50399
           Summary: [c++11] Lookup error w/ enums
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: blelbach@cct.lsu.edu


$ cat cxx11_enum_lookup_bug.cpp 
namespace A {

namespace B {

void F() { }

}

namespace C {

enum B { };

void G() { B::F(); } 

}

}

$ /usr/lib/gcc-snapshot/bin/g++ --version
g++ (Debian 20110816-1) 4.7.0 20110816 (experimental) [trunk revision 177785]
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ /usr/lib/gcc-snapshot/bin/g++ cxx11_enum_lookup_bug.cpp -c
$ /usr/lib/gcc-snapshot/bin/g++ cxx11_enum_lookup_bug.cpp -c -std=c++0x
cxx11_enum_lookup_bug.cpp: In function 'void A::C::G()':
cxx11_enum_lookup_bug.cpp:13:12: error: 'F' is not a member of 'A::C::B'
$ g++-4.6 --version
g++-4.6 (Debian 4.6.1-8) 4.6.1
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ g++-4.6 cxx11_enum_lookup_bug.cpp -c
$ g++-4.6 cxx11_enum_lookup_bug.cpp -c -std=c++0x
cxx11_enum_lookup_bug.cpp: In function ‘void A::C::G()’:
cxx11_enum_lookup_bug.cpp:13:12: error: ‘F’ is not a member of ‘A::C::B’
$ g++-4.5 --version
g++-4.5 (Debian 4.5.3-8) 4.5.3
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ g++-4.5 cxx11_enum_lookup_bug.cpp -c
$ g++-4.5 cxx11_enum_lookup_bug.cpp -c -std=c++0x
cxx11_enum_lookup_bug.cpp: In function ‘void A::C::G()’:
cxx11_enum_lookup_bug.cpp:13:12: error: ‘F’ is not a member of ‘A::C::B’
$ g++-4.4 --version
g++-4.4 (Debian 4.4.6-8) 4.4.6
Copyright (C) 2010 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ g++-4.4 cxx11_enum_lookup_bug.cpp -c
$ g++-4.4 cxx11_enum_lookup_bug.cpp -c -std=c++0x
cxx11_enum_lookup_bug.cpp: In function ‘void A::C::G()’:
cxx11_enum_lookup_bug.cpp:13: error: ‘F’ is not a member of ‘A::C::B’

[Bug c++/50399] [c++11] Lookup error w/ enums

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50399

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-09-15 09:21:30 UTC ---
I think G++ is correct, see [basic.lookup.qual]

In C++03 a nested-name-specifier can only refer to a class or namespace, in
C++11 it can also refer to an enumeration.

[Bug c++/50399] [c++11] Lookup error w/ enums

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50399

Jonathan Wakely <redi at gcc dot gnu.org> changed:

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

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-09-15 09:26:38 UTC ---
C++03 says "During the lookup for a name preceding the :: scope resolution
operator, object, function, and enumerator names are ignored."

So in -std=c++98 mode G++ is correct to ignore A::C::B and so finds B::F (Clang
gets this wrong)

In C++11 the enumeration is not ignored (because a nested-name-specifier could
refer to a scoped enumeration) so name lookup finds B in the enclosing
namespace, i.e. A::C::B