From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-406792-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 1827 invoked by alias); 15 Nov 2012 20:57:06 -0000
Received: (qmail 1763 invoked by uid 48); 15 Nov 2012 20:56:47 -0000
From: "luto at mit dot edu" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/55347] New: Specialized member of class template prevents visibility setting
Date: Thu, 15 Nov 2012 20:57:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: luto at mit dot edu
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields:
Message-ID: <bug-55347-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2012-11/txt/msg01454.txt.bz2


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.