[Bug c++/53627] New: perfect forwarding for static int member

[Bug c++/53627] New: perfect forwarding for static int member

[mikhail_semenov at hotmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

             Bug #: 53627
           Summary: perfect forwarding for static int member
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: mikhail_semenov@hotmail.com


Created attachment 27600
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27600
The program file

The following program fails to link with the ld error report 

C:\Users\Mikhail\AppData\Local\Temp\cc0HPRb8.o:perfect_forwarding_for_static_mem
ber.cpp:(.text+0x106): undefined reference to `Z::n'
collect2.exe: error: ld returned 1 exit status


#include <iostream>
#include <string>
#include <memory.h>

struct Z
{ 
       static const double x; 
       static  double y;       
       static const int n = 1000;
       const  double p;
       Z():p(0.1){};
}; 

const double Z::x = 33.2;
double Z::y = 55.7;

void a(double d)
{
      std::cout << "a(double): " << d << std::endl;
}


void a(int k)
{
    std::cout << "a(int): " << k << std::endl;
}

template<class T>
void call(T&& x)
{       
     a(std::forward<T>(x));      
}


int main()
{
      int i = 10;
      double x = 7.5;
      static const double y = 2278.1;
      a(i);
      a(x);
      a(y);
      call(Z::x);
      call(Z::y);
      call(Z().p);
      call(Z::n);    
      return 0;          
}

[Bug c++/53627] perfect forwarding for static int member

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

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

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

--- Comment #1 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-06-10 20:29:16 UTC ---
You are missing a definition of n:

const int Z::n;

[Bug c++/53627] perfect forwarding for static int member

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

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

--- Comment #2 from Manuel López-Ibáñez <manu at gcc dot gnu.org> 2012-06-10 21:03:16 UTC ---
This is exactly: 

http://gcc.gnu.org/wiki/VerboseDiagnostics#missing_static_const_definition

[Bug c++/53627] perfect forwarding for static int member

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

--- Comment #3 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-06-10 21:11:41 UTC ---
This does not look like a compiler defect to me. Z::n has never been defined
but is odr-used.

[Bug c++/53627] perfect forwarding for static int member

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

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

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

--- Comment #4 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-06-10 21:23:05 UTC ---
(In reply to comment #2)
> This is exactly: 
> 
> http://gcc.gnu.org/wiki/VerboseDiagnostics#missing_static_const_definition

I agree. But let me just add that the first of the examples provided there
("return argc > 1 ? S::a : S::b;") should no longer me listed (or be modified),
because that was fixed with C++11 due to 

http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#712

This situation should no longer require a definition for S::a or S::b.

[Bug c++/53627] perfect forwarding for static int member

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

--- Comment #5 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-06-10 21:26:27 UTC ---
(In reply to comment #4)
> (In reply to comment #2)
> > This is exactly: 
> > 
> > http://gcc.gnu.org/wiki/VerboseDiagnostics#missing_static_const_definition
> 
> I agree. But let me just add that the first of the examples provided there
> ("return argc > 1 ? S::a : S::b;") should no longer me listed (or be modified),
> because that was fixed with C++11 due to 
> 
> http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#712
> 
> This situation should no longer require a definition for S::a or S::b.

I just recognize that this example *does* require a definition for S::a and
S::b in C++11 mode. I open a new issue for this.

[Bug c++/53627] perfect forwarding for static int member

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-06-10 21:37:38 UTC ---
I've updated the wiki with words to that effect

[Bug c++/53627] perfect forwarding for static int member

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-06-10 21:50:18 UTC ---
(In reply to comment #4)
> because that was fixed with C++11 due to 
> 
> http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#712
> 
> This situation should no longer require a definition for S::a or S::b.

Unless I'm mistaken DR 712 was not fixed in time for C++11, I don't see it in
N3290

[Bug c++/53627] perfect forwarding for static int member

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

--- Comment #8 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-06-11 06:47:42 UTC ---
(In reply to comment #7)
> (In reply to comment #4)
> > because that was fixed with C++11 due to 
> > 
> > http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#712
> > 
> > This situation should no longer require a definition for S::a or S::b.
> 
> Unless I'm mistaken DR 712 was not fixed in time for C++11, I don't see it in
> N3290

Agreed, DR 712 is a post-C11 resolution.

--- Comment #9 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-06-11 06:48:13 UTC ---
(In reply to comment #7)
> (In reply to comment #4)
> > because that was fixed with C++11 due to 
> > 
> > http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#712
> > 
> > This situation should no longer require a definition for S::a or S::b.
> 
> Unless I'm mistaken DR 712 was not fixed in time for C++11, I don't see it in
> N3290

Agreed, DR 712 is a post-C++11 resolution.

[Bug c++/53627] perfect forwarding for static int member

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53627

--- Comment #8 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-06-11 06:47:42 UTC ---
(In reply to comment #7)
> (In reply to comment #4)
> > because that was fixed with C++11 due to 
> > 
> > http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#712
> > 
> > This situation should no longer require a definition for S::a or S::b.
> 
> Unless I'm mistaken DR 712 was not fixed in time for C++11, I don't see it in
> N3290

Agreed, DR 712 is a post-C11 resolution.