[Bug c++/46075] New: g++ wrongly lookups builtin types in ADL (compiles wrong code)

[slyfox at inbox dot ru]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46075

           Summary: g++ wrongly lookups builtin types in ADL (compiles
                    wrong code)
           Product: gcc
           Version: 4.4.5
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: sly...@inbox.ru


clang++ and comeau don't compile following code:

inst.cc:17:9: error: use of undeclared identifier 'my_foo'
        my_foo ((const T *)0);
        ^
inst.cc:36:7: note: in instantiation of member function 'my_T<char>::my_T'
requested here
User::User() { }
      ^
1 error generated.

// ------------------ inst.cc ---------------------------------

// http://blog.llvm.org/2009/12/dreaded-two-phase-name-lookup.html

// should fail

// 23:01:10 < dgregor> slyfox_: Clang is correct
// 23:01:39 < slyfox_> dgregor: how can i make this code compile with clang w/o
moving declaration upper?
// 23:02:49 < dgregor> you'll need to move the declaration up, or instantiate
my_T with a non-builtin type (so that 
//                     argument-dependent lookup can find my_foo in the
namespace of that type)
// 23:03:27 < slyfox_> so builtin types are special
// 23:04:02 < dgregor> not special, really; they have no "associated
namespaces", i.e., there's nowhere for the compiler to l
ook 
//                     at instantiation time

template<typename T> struct my_T {
    my_T()
    {
        // this one explicitely mentions 'T' as one of params
        my_foo ((const T *)0);

        // this one would be 'T' independent, and gcc will report
        // an error it i'll try to use this one instead.
        //my_foo((const T *)0);
    }
};

struct User {
    User(); // explicit c-tor
    my_T<char> t;
};

// we specialize my_foo for 'const char *'
static void my_foo (const char *) {}

// To be checked. Should work too
//static void my_foo(const void *) {}

User::User() { }

int main()
{
    User u;
    return 0;
}