[Bug c++/39786] New: Qualified name lookup through different numbers of using directives

["hstong at ca dot ibm dot com" <gcc-bugzilla@gcc.gnu.org>]

It appears that qualified name lookup fails to find the correct candidate set
for overload resolution in the test case below.

For the following test case, the symptom is rejects-valid; however, it is
simple
to produce variants for wrong-code and accepts-invalid.

The Comeau online compiler compiles the test case successfully.

ISO/IEC 14882:2003 Sub-clause 3.4.3.2 [namespace.qual] paragraph 2:
===
Given X::m (where X is a user-declared namespace), or given ::m (where X is the
global namespace), let
S be the set of all declarations of m in X and in the transitive closure of all
namespaces nominated by
using-directives in X and its used namespaces, except that using-directives are
ignored in any namespace,
including X, directly containing one or more declarations of m.  No namespace
is searched more than once
in the lookup of a name.  If S is the empty set, the program is ill-formed. 
Otherwise, if S has exactly one
member, or if the context of the reference is a using-declaration (7.3.3), S is
the required set of declarations
of m.  Otherwise if the use of m is not one that allows a unique declaration to
be chosen from S, the program
is ill-formed.
===

We are looking for `f' from the global namespace.  The global namespace does
not directly contain a declaration
of `f'.  There are two namespaces nominated by using-directives in the global
namespace, ::A and ::B.

There are no using-directives in ::A.  ::B does not directly contain a
declaration of `f'.  There is a using-
directive in ::B nominating ::B::C.  There are no using-directives in ::B::C.

S is { ::A::f(char *), ::B::C::f(int) } and overload resolution on the call
`::f(0)' should pick ::B::C::f(int).

### Self-contained source (namelookup.C):
namespace A {
    char (*f(char *p))[13] { return 0; }
}

namespace B {
    namespace C {
        char (*f(int p))[42] { return 0; }
    }
    using namespace C;
}

using namespace B;
using namespace A;

char x[sizeof *::f(0) == 42 ? 1 : -1];


### Command to reproduce:
g++ -c namelookup.C


### Compiler output:
namelookup.C:15: error: size of array x is negative


### g++ -v output:
Using built-in specs.
Target: powerpc64-suse-linux
Configured with: ../configure --prefix=/usr --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib64 --libexecdir=/usr/lib64
--enable-languages=c,c++,objc,fortran,obj-c++,java --enable-checking=release
--with-gxx-include-dir=/usr/include/c++/4.3 --enable-ssp --disable-libssp
--with-bugurl=http://bugs.opensuse.org/ --with-pkgversion='SUSE Linux'
--disable-libgcj --disable-libmudflap --with-slibdir=/lib64 --with-system-zlib
--enable-__cxa_atexit --enable-libstdcxx-allocator=new --disable-libstdcxx-pch
--enable-version-specific-runtime-libs --program-suffix=-4.3
--enable-linux-futex --without-system-libunwind --with-cpu=power4
--enable-secureplt --with-long-double-128 --build=powerpc64-suse-linux
Thread model: posix
gcc version 4.3.2 [gcc-4_3-branch revision 141291] (SUSE Linux)


-- 
           Summary: Qualified name lookup through different numbers of using
                    directives
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hstong at ca dot ibm dot com
 GCC build triplet: powerpc64-suse-linux
  GCC host triplet: powerpc64-suse-linux
GCC target triplet: powerpc64-suse-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39786