[Bug c++/53464] New: Invalid default value for non-type template parameter is accepted

[Bug c++/53464] New: Invalid default value for non-type template parameter is accepted

[schwan@uni-mainz.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53464

             Bug #: 53464
           Summary: Invalid default value for non-type template parameter
                    is accepted
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: schwan@uni-mainz.de


Consider the following code:

template <int value>
struct bar
{
    static constexpr int get()
    {
        return value;
    }
};

template <typename A, int value = A::get()>
struct foo
{
};

int main()
{
    typedef foo<bar<0>> type;

    return 0;
}

It should be rejected, since A::get() is not a "converted constant expression"
as discussed in http://stackoverflow.com/questions/10721130 . I tested this
with the GCC from svn.

[Bug c++/53464] Invalid default value for non-type template parameter is accepted

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53464

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> 2012-05-24 07:19:28 UTC ---
I don't see why the expression A::get() should not be a converted constant
expression of the type of the template parameter, please be more specific. The
rationale provided in the referenced link does not sound convincing to me. 

In the context of the instantiation the expression A::get() is a prvalue core
constant expression of int type, thus it is a literal constant expression of
int type. It is also a converted constant expression of type int, because
A::get() already has the type int (after instantiation).

[Bug c++/53464] Invalid default value for non-type template parameter is accepted

[schaub.johannes at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53464

Johannes Schaub <schaub.johannes at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |schaub.johannes at
                   |                            |googlemail dot com

--- Comment #2 from Johannes Schaub <schaub.johannes at googlemail dot com> 2012-05-24 07:51:09 UTC ---
Daniel, nice to meet you again :)

See my SO answer and Richard's opinion at
http://stackoverflow.com/a/10727719/34509 .

[Bug c++/53464] Invalid default value for non-type template parameter is accepted

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53464

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-05-24 10:48:58 UTC ---
Invalid then, thanks.

[Bug c++/53464] Invalid default value for non-type template parameter is accepted

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53464

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

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

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-05-24 11:27:10 UTC ---
The testcase would be nice for the testsuite though.

[Bug c++/53464] Invalid default value for non-type template parameter is accepted

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53464

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-05-24 11:39:10 UTC ---
Later today I will add it.

[Bug c++/53464] Invalid default value for non-type template parameter is accepted

[paolo at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53464

--- Comment #6 from paolo at gcc dot gnu.org <paolo at gcc dot gnu.org> 2012-05-24 15:12:45 UTC ---
Author: paolo
Date: Thu May 24 15:12:37 2012
New Revision: 187842

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=187842
Log:
2012-05-24  Paolo Carlini  <paolo.carlini@oracle.com>

    PR c++/53464
    * g++.dg/cpp0x/constexpr-default1.C: New.


Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/constexpr-default1.C
Modified:
    trunk/gcc/testsuite/ChangeLog