[Bug c++/48582] New: Template non-type arguments doesn't accept null pointer constant value

[Bug c++/48582] New: Template non-type arguments doesn't accept null pointer constant value

[boostcpp at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48582

           Summary: Template non-type arguments doesn't accept null
                    pointer constant value
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: boostcpp@gmail.com


According to current C++0x draft 14.3.2 [temp.arg.nontype],
template non-type arguments can be a constant expression that evaluates to a
null pointer value or null member pointer value.
This change was made in n1905.

So the following code is well-formed.

template < void * = nullptr > void f() { }

int main()
{
    f() ;
    f<nullptr>() ;
    f<0>() ;

    constexpr void * ptr = nullptr ;
    f<ptr>() ;
}

But current gcc does not accept it.
Or is this just unimplemented feature?

[Bug c++/48582] Template non-type arguments doesn't accept null pointer constant value

[gintensubaru at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48582

--- Comment #1 from Takaya Saito <gintensubaru at gmail dot com> 2011-08-25 20:09:49 UTC ---
Current C++0x draft 14.3.2/5 says 0 is not a valid template-argument
for a non-type template-parameter of pointer type.

So, `f<0>();' is ill-formed, as current gcc rejects it.

But 14.3.2/5 says both `(void*)0' and `nullptr' are valid,
so the other codes should be accepted.

[Bug c++/48582] [C++0x] [DR 342] Template non-type arguments doesn't accept null pointer constant value

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48582

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2011-08-27
         AssignedTo|unassigned at gcc dot       |jason at gcc dot gnu.org
                   |gnu.org                     |
            Summary|Template non-type arguments |[C++0x] [DR 342] Template
                   |doesn't accept null pointer |non-type arguments doesn't
                   |constant value              |accept null pointer
                   |                            |constant value
     Ever Confirmed|0                           |1

[Bug c++/48582] [C++0x] [DR 342] Template non-type arguments doesn't accept null pointer constant value

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48582

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> 2011-08-28 15:38:33 UTC ---
Author: jason
Date: Sun Aug 28 15:38:29 2011
New Revision: 178144

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=178144
Log:
    Core DR 342
    PR c++/48582
    * pt.c (check_valid_ptrmem_cst_expr): A null member pointer value
    is valid in C++11.
    (convert_nontype_argument): Likewise.  Implicitly convert nullptr
    and do constant folding.
    * mangle.c (write_template_arg_literal): Mangle null member
    pointer values as 0.
    * call.c (null_member_pointer_value_p): New.
    * cp-tree.h: Declare it.

Added:
    trunk/gcc/testsuite/g++.dg/abi/mangle50.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/mangle.c
    trunk/gcc/cp/pt.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/48582] [C++0x] [DR 342] Template non-type arguments doesn't accept null pointer constant value

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48582

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.7.0

--- Comment #3 from Jason Merrill <jason at gcc dot gnu.org> 2011-08-28 15:39:14 UTC ---
Implemented for 4.7.