[Bug c++/56693] New: Fail to ignore const qualification on top of a function type.

[Bug c++/56693] New: Fail to ignore const qualification on top of a function type.

[cassio.neri at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56693

             Bug #: 56693
           Summary: Fail to ignore const qualification on top of a
                    function type.
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: cassio.neri@gmail.com


The following code:

void f() {}

template <typename T> void g(const T*) { }

int main() {
    g(f);
}

raises an error with this note:

    types 'const T' and 'void()' have incompatible cv-qualifiers

Attempting to instantiate g creates a function that takes a pointer to a const
T where T = void(). Since there's no such thing as a "const function", this
explains the note. However, C++11 8.3.5/6 says

"The effect of a cv-qualifier-seq in a function declarator is not the same as
adding cv-qualification on top of the function type. In the latter case, the
cv-qualifiers are ignored."

Hence, the const qualifier should be ignored and the code should compile. (It
does compile with clang and visual studio.)

For more information see:
http://stackoverflow.com/questions/15578298/can-a-const-t-match-a-pointer-to-free-function

[Bug c++/56693] Fail to ignore const qualification on top of a function type.

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56693

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler at
                   |                            |googlemail dot com

--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2013-03-23 12:20:30 UTC ---
This looks like

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

to me
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Subject: [Bug libfortran/56696] [4.8/4.9 Regression] Formatted (list-directed)  input fails to signal end of record
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idV696

Dominique d'Humieres <dominiq at lps dot ens.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-03-23
                 CC|                            |jvdelisle at gcc dot
                   |                            |gnu.org
            Summary|Formatted (list-directed)   |[4.8/4.9 Regression]
                   |input fails to signal end   |Formatted (list-directed)
                   |of record                   |input fails to signal end
                   |                            |of record
     Ever Confirmed|0                           |1

--- Comment #1 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2013-03-23 12:23:33 UTC ---
The test works for revision 194721 (2012-12-26), but not for revision 194897
(2013-01-04). From the change log, it seems likely to be revision 194809
(pr55818). Revisions 194724 (pr48960) and 194734 (pr48976) are also in the
range, but don't seem related.

[Bug c++/56693] [DR 1584] Fail to ignore const qualification on top of a function type.

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56693

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |SUSPENDED
   Last reconfirmed|                            |2013-03-23
            Summary|Fail to ignore const        |[DR 1584] Fail to ignore
                   |qualification on top of a   |const qualification on top
                   |function type.              |of a function type.
     Ever Confirmed|0                           |1

[Bug c++/56693] [DR 1584] Fail to ignore const qualification on top of a function type.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56693

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---

Notes from the May, 2015 meeting:

The consensus of CWG was that the cv-qualification of the argument and
parameter must match, so the original example should be rejected.