[Bug c++/46105] New: Ordering failure among partial specializations with non-deduced context

[Bug c++/46105] New: Ordering failure among partial specializations with non-deduced context

[potswa at mac dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

           Summary: Ordering failure among partial specializations with
                    non-deduced context
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: potswa@mac.com


See attachment.

The second arguments of the two partial specializations evaluate to "void." If
void is substituted manually, the code works fine. (But the desired SFINAE side
effect is removed.)

As neither such argument contains a parameter in a deduced context, they should
not participate in deduction. Once the partial specialization has been
determined to match, the parameters should be substituted and evaluated to
simply void.

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[potswa at mac dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

--- Comment #1 from David Krauss <potswa at mac dot com> 2010-10-20 21:15:27 UTC ---
Created attachment 22098
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22098
small example

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[potswa at mac dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

David Krauss <potswa at mac dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #22098|0                           |1
        is obsolete|                            |

--- Comment #2 from David Krauss <potswa at mac dot com> 2010-10-20 21:18:02 UTC ---
Created attachment 22099
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22099
third time's a charm… content type autodetect failed

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-10-20 21:39:23 UTC ---
(you can edit an existing attachment to set the content type)

thanks for the nice minimal testcase, that's very useful

I *think* this is a dup of another bug I've seen in bugzilla but I can't find
it right now

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> 2010-10-27 20:53:14 UTC ---
The error message that GCC gives is:
t.cc:25:22: error: ambiguous class template instantiation for ‘struct
element<const has_et>’
t.cc:12:8: error: candidates are: struct element<T, typename empty<typename
T::element_type>::type>
t.cc:17:8: error:                 struct element<const T, typename
empty<typename T::element_type>::type>
t.cc:25:1: error: ‘type’ in class ‘element<const has_et>’ does not name a type


T is "const has_et" for the first candidate and T is has_et for the second. 
Maybe I am missing something here but both T's have an element_type.

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-10-27 21:03:50 UTC ---
I think the point is that the element<T const> partial specialization should be
preferred, but GCC considers them ambiguous, and uses the primary template.

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jason at gcc dot gnu.org

--- Comment #6 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-09-25 12:49:59 UTC ---
Jason, is this the same as PR45012?

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

--- Comment #7 from Jason Merrill <jason at gcc dot gnu.org> 2011-09-26 18:24:36 UTC ---
It looks the same to me.

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |paolo.carlini at oracle dot
                   |                            |com
         Resolution|                            |DUPLICATE

--- Comment #8 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-09-26 18:28:15 UTC ---
Thanks, let's resolve as duplicate.

*** This bug has been marked as a duplicate of bug 45012 ***

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

--- Comment #9 from Jason Merrill <jason at gcc dot gnu.org> 2011-09-27 02:12:55 UTC ---
Author: jason
Date: Tue Sep 27 02:12:51 2011
New Revision: 179229

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=179229
Log:
    PR c++/46105
    * typeck.c (structural_comptypes): Ignore cv-quals on typename scope.

Added:
    trunk/gcc/testsuite/g++.dg/template/partial12.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/typeck.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

--- Comment #10 from Jason Merrill <jason at gcc dot gnu.org> 2011-09-27 02:19:09 UTC ---
Author: jason
Date: Tue Sep 27 02:19:05 2011
New Revision: 179232

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=179232
Log:
    PR c++/46105
    * typeck.c (structural_comptypes): Ignore cv-quals on typename scope.

Added:
    branches/gcc-4_6-branch/gcc/testsuite/g++.dg/template/partial12.C
Modified:
    branches/gcc-4_6-branch/gcc/cp/ChangeLog
    branches/gcc-4_6-branch/gcc/cp/typeck.c
    branches/gcc-4_6-branch/gcc/testsuite/ChangeLog

[Bug c++/46105] Ordering failure among partial specializations with non-deduced context

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46105

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|DUPLICATE                   |FIXED
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |
   Target Milestone|---                         |4.6.2

--- Comment #11 from Jason Merrill <jason at gcc dot gnu.org> 2011-09-27 02:21:53 UTC ---
Fixed.