[Bug c++/55347] New: Specialized member of class template prevents visibility setting

[Bug c++/55347] New: Specialized member of class template prevents visibility setting

[luto at mit dot edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55347

             Bug #: 55347
           Summary: Specialized member of class template prevents
                    visibility setting
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: luto@mit.edu


Compiling this code:

--- cut here ---
template<typename T>
class A
{
  void func() {}
};

//#pragma GCC visibility push(default) -- no effect

template<> void A<int>::func() {}  // This causes a problem
template class __attribute__((visibility("default"))) A<int>;

//#pragma GCC visibility pop
--- cut here ---

results in:

template_visibility.cc:10:55: warning: type attributes ignored after type is
already defined [-Wattributes]

The emitted code ends up hidden.

This is a minor issue in C++98 (I'm not sure why you'd want to do this), but
it's an actual problem in C++11: extern templates behave the same way.

I think that gcc's behavior is consistent, but there should be a way to
override the visibility of a particular class template specialization *without
instantiating/defining it*, then specialize a member, then instantiate the
template.