[Bug c++/53540] New: C++11: using fails to be equivalent to typedef

[Bug c++/53540] New: C++11: using fails to be equivalent to typedef

[akim.demaille at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

             Bug #: 53540
           Summary: C++11: using fails to be equivalent to typedef
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: akim.demaille@gmail.com


Created attachment 27532
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27532
test case

Hi all,

I hope this is not a bogus bug report, I apologize if there is something I
misunderstood.  I observed the following with both 4.7.0 and "4.8":

g++-mp-4.7 (MacPorts gcc47 4.7.0_3) 4.7.0
Copyright (C) 2012 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++-mp-4.8 (MacPorts gcc48 4.8-20120527_1) 4.8.0 20120527 (experimental)
Copyright (C) 2012 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.

In the following example, I import a type name from a templates struct with
"using", and do the same with "typedef".  The latter works, but "using" does
not seem to find the definition.  clang finds it though (but then again, my
understanding might be wrong).

If "function" is not templated, there is no problem.


$ cat foo.cc
template <typename T>
struct context
{
  typedef int type;
};

template <typename T>
void function()
{
  using ctx1 = context<T>;
  typename ctx1::type f1;

  typedef context<T> ctx2;
  typename ctx2::type f2;
}

int main()
{
  function<int>();
}


$ g++-mp-4.8 -Wall -std=c++11 foo.cc
foo.cc: In instantiation of 'void function() [with T = int]':
foo.cc:19:17:   required from here
foo.cc:11:23: error: no type named 'type' in 'using ctx1 = struct context<T>'
   typename ctx1::type f1;
                       ^
foo.cc:14:23: warning: unused variable 'f2' [-Wunused-variable]
   typename ctx2::type f2;
                       ^

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2012-05-31
                 CC|                            |dodji at gcc dot gnu.org
     Ever Confirmed|0                           |1

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-05-31 17:42:41 UTC ---
I think it's valid, CC'ing Dodji for confirmation.

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[akim.demaille at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

--- Comment #2 from Akim Demaille <akim.demaille at gmail dot com> 2012-06-11 17:27:13 UTC ---
(In reply to comment #1)
> I think it's valid, CC'ing Dodji for confirmation.

Any news?

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[dodji at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

Dodji Seketeli <dodji at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |dodji at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #3 from Dodji Seketeli <dodji at gcc dot gnu.org> 2012-08-16 19:09:39 UTC ---
Sorry, I am getting to this just now.

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[dodji at seketeli dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

--- Comment #4 from dodji at seketeli dot org <dodji at seketeli dot org> 2012-08-16 19:11:01 UTC ---
> I think it's valid, CC'ing Dodji for confirmation.

I agree this is a bug.  I am looking into it.

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[dodji at seketeli dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

--- Comment #5 from dodji at seketeli dot org <dodji at seketeli dot org> 2012-08-16 22:18:36 UTC ---
A candidate patch was sent to 
http://gcc.gnu.org/ml/gcc-patches/2012-08/msg01111.html.

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-10-05 21:29:25 UTC ---
Dodji, time to ping? ;)

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[dodji at seketeli dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

--- Comment #7 from dodji at seketeli dot org <dodji at seketeli dot org> 2012-10-08 14:26:37 UTC ---
"paolo.carlini at oracle dot com" <gcc-bugzilla@gcc.gnu.org> a écrit:

> Dodji, time to ping? ;)

Right:  http://gcc.gnu.org/ml/gcc-patches/2012-10/msg00766.html.

:)

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[dodji at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

--- Comment #8 from Dodji Seketeli <dodji at gcc dot gnu.org> 2012-10-10 10:44:02 UTC ---
Author: dodji
Date: Wed Oct 10 10:43:53 2012
New Revision: 192304

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=192304
Log:
PR c++/53540 - using fails to be equivalent to typedef

In the example of this problem report, during the substituting of int
into 'function', tsubst_aggr_type fails for the alias ctxt1.  This is
because TYPE_TEMPLATE_INFO looks for the TEMPLATE_INFO of the ctxt1
alias at the wrong place and was wrongly finding it to be NULL.
Namely, it was looking for it in the DECL_TEMPLATE_INFO of the
declaration of the type -- as if ctxt1 was an alias template
specialization -- rather than looking for it in its
CLASSTYPE_TEMPLATE_INFO.

Fixed thus.  The other hunks of the patch are a cleanup to make a
better use of alias_template_specialization_p.

Bootstrapped and tested on x86_64-unknown-linux-gnu against trunk.

gcc/cp

    * cp-tree.h (TYPE_TEMPLATE_INFO): For an alias that is not an
    instance of alias template, don't look for its TEMPLATE_INFO in
    its declaration.
    (alias_template_specialization_p): Take const_tree.
    * pt.c (alias_template_specialization_p): Take a const_tree.
    Don't call primary_template_instantiation_p.
    (primary_template_instantiation_p): Call
    alias_template_specialization_p.

gcc/testsuite/

    * g++.dg/cpp0x/alias-decl-24.C: New test.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/alias-decl-24.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[dodji at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

Dodji Seketeli <dodji at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #9 from Dodji Seketeli <dodji at gcc dot gnu.org> 2012-10-10 10:57:38 UTC ---
Fixed in trunk (4.8)

[Bug c++/53540] C++11: using fails to be equivalent to typedef

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53540

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |paul at preney dot ca

--- Comment #10 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-05-03 09:54:21 UTC ---
*** Bug 54309 has been marked as a duplicate of this bug. ***