[Bug c++/57466] New: Argument deduction fails for 'const T*' when T is function type

[Bug c++/57466] New: Argument deduction fails for 'const T*' when T is function type

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

            Bug ID: 57466
           Summary: Argument deduction fails for 'const T*' when T is
                    function type
           Product: gcc
           Version: 4.7.3
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
            Blocks: 57465

(This is the root cause of PR 57465, but I have a workaround for the library.)


template<typename T>
  constexpr bool
  is_pointer(const T*)
  { return true; }

template<typename T>
  constexpr bool
  is_pointer(const T&)
  { return false; }

using F = void();

constexpr F* f = nullptr;

static_assert( is_pointer(f), "function pointer is a pointer" );

G++ fails the static assertion:

t.cc:15:1: error: static assertion failed: function pointer is a pointer
 static_assert( is_pointer(f), "function pointer is a pointer" );
 ^

The first function template should be instantiated as bool is_pointer(F*) but
instead deduction fails because:
   types 'const T' and 'F {aka void()}' have incompatible cv-qualifiers


Note deduction succeeds with an explicit template argument:

template<typename T>
  constexpr bool
  is_pointer(const T*)
  { return true; }

using F = void();

constexpr F* f = nullptr;

constexpr bool pass = is_pointer<F>(f);
constexpr bool fail = is_pointer(f);

[Bug c++/57466] Argument deduction fails for 'const T*' when T is function type

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler@googlemail.
                   |                            |com

--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
I think this observation was the reason why I filed:

http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1584

Notice that albeit the current CWG issue status contains a P/R, there is
indication for being some contradiction to the assertions made in

www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#503

(I have posted this to the CWG committee recently)
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From: "vladimir.fuka at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/57469] New: Erroneous warning for unused dummy arguments used in namelist
Date: Thu, 30 May 2013 11:14:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idW469

            Bug ID: 57469
           Summary: Erroneous warning for unused dummy arguments used in
                    namelist
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vladimir.fuka at gmail dot com

This code:

   subroutine read_command_line(line,a,b)
     character(*),intent(in) :: line
     intent(inout) :: a,b
     namelist /cmd/ a,b

     read(line,nml = cmd)
   end

produces this warning with gfortran-4.8 20130509:

gfortran warning.f90 -c -Wall
warning.f90:1.38:

   subroutine read_command_line(line,a,b)
                                      1
Warning: Unused dummy argument 'a' at (1)
warning.f90:1.40:

   subroutine read_command_line(line,a,b)
                                        1
Warning: Unused dummy argument 'b' at (1)




For intent(out) it produces:

Warning: Dummy argument 'a' at (1) was declared INTENT(OUT) but was not set

But i understand it may be correct.

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |SUSPENDED
   Last reconfirmed|                            |2013-05-30
            Summary|Argument deduction fails    |[DR 1584] Argument
                   |for 'const T*' when T is    |deduction fails for 'const
                   |function type               |T*' when T is function type
     Ever confirmed|0                           |1

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Ah yes, thanks!

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|SUSPENDED                   |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |paolo.carlini at oracle dot com

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> ---
DR1584 is Ready.

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[paolo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

--- Comment #4 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> ---
Author: paolo
Date: Wed Jul  9 21:23:06 2014
New Revision: 212410

URL: https://gcc.gnu.org/viewcvs?rev=212410&root=gcc&view=rev
Log:
/cp
2014-07-09  Paolo Carlini  <paolo.carlini@oracle.com>

    DR 1584
    PR c++/57466
    * pt.c (check_cv_quals_for_unify): Implement resolution, disregard
    cv-qualifiers of function types.

/testsuite
2014-07-09  Paolo Carlini  <paolo.carlini@oracle.com>

    DR 1584
    PR c++/57466
    * g++.dg/template/pr57466.C: New.
    * g++.dg/cpp0x/pr57466.C: Likewise.
    * g++.dg/template/unify6.C: Update.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/pr57466.C
    trunk/gcc/testsuite/g++.dg/template/pr57466.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/template/unify6.C

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
           Assignee|paolo.carlini at oracle dot com    |unassigned at gcc dot gnu.org
   Target Milestone|---                         |4.10.0

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Fixed for 4.10.

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[paolo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

--- Comment #6 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> ---
Author: paolo
Date: Fri Aug 15 16:23:47 2014
New Revision: 214027

URL: https://gcc.gnu.org/viewcvs?rev=214027&root=gcc&view=rev
Log:
/cp
2014-08-15  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/62072
    Revert:
    2014-07-09  Paolo Carlini  <paolo.carlini@oracle.com>

    DR 1584
    PR c++/57466
    * pt.c (check_cv_quals_for_unify): Implement resolution, disregard
    cv-qualifiers of function types.

/testsuite
2014-08-15  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/62072
    Revert:
    2014-07-09  Paolo Carlini  <paolo.carlini@oracle.com>

    DR 1584
    PR c++/57466
    * g++.dg/template/pr57466.C: New.
    * g++.dg/cpp0x/pr57466.C: Likewise.
    * g++.dg/template/unify6.C: Update.

    * g++.dg/cpp0x/sfinae52.C: New.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/sfinae52.C
Removed:
    trunk/gcc/testsuite/g++.dg/cpp0x/pr57466.C
    trunk/gcc/testsuite/g++.dg/template/pr57466.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/template/unify6.C

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

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

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

--- Comment #7 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Patch reverted, unfortunately.

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.0                         |5.2

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 5.1 has been released.

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.2                         |5.3

--- Comment #10 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 5.2 is being released, adjusting target milestone to 5.3.

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

--- Comment #19 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Jonathan Wakely from comment #17)
> Fine by me.
> 
> EDG agrees with GCC, but Clang accepts the original example. I guess they'll
> change when 1584 gets resolved.

clang started to reject in clang 7.0.0.

Is there anything else that needs to be done?

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

--- Comment #20 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The core issue is still open, for some reason.

[Bug c++/57466] [DR 1584] Argument deduction fails for 'const T*' when T is function type

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57466

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|5.5                         |---