[Bug c++/11540] New: Redefinition of default arguments allowed for template functions

[Bug c++/11540] New: Redefinition of default arguments allowed for template functions

[philippe dot haution at mines-paris dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540

           Summary: Redefinition of default arguments allowed for template
                    functions
           Product: gcc
           Version: 3.2.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: philippe dot haution at mines-paris dot org
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu

The following code is deemed legal by gcc, although it breaks the one definition
per translation unit rule :

testcase.cc :
-----------------------
namespace ns
{
  template<typename Tv>
  int convert_from_v(Tv v, int prec = -1)
  { return 1; }

}

namespace ns
{
  template<typename Tv>
  int convert_from_v(Tv v, int prec = -2);

}

int main()
{
  return ns::convert_from_v<int>(1);
}

$ g++ testcase.cc -o testcase
$ testcase
$ echo $?
255

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[bangerth at dealii dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540


bangerth at dealii dot org changed:

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


------- Additional Comments From bangerth at dealii dot org  2003-07-16 14:02 -------
The code is legal: first, there is only one definition (but two declarations),
so the one-definition rule is inapplicable. Besides a violation of the ODR 
does not require a diagonstic.

On the other hand, 8.6.3/4 specifically allows your case, saying that 
default arguments defined in different scopes have completely independent
values.

W.

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[nathan at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540


nathan at gcc dot gnu dot org changed:

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


------- Additional Comments From nathan at gcc dot gnu dot org  2003-07-16 14:16 -------
Wolfgang, they are in the same scope though.

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[bangerth at dealii dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540


bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2003-07-16 14:39:52
               date|                            |


------- Additional Comments From bangerth at dealii dot org  2003-07-16 14:39 -------
Um, why? The namespace is closed and then opened again. Isn't this two
different scopes?

Alas, you have a point -- sorry for being so quick in closing the PR. 
I made a couple of more experiments. We don't get a warning when I don't
close and reopen the namespace. On the other hand, I _do_ get a warning
when the function is not a template, with or without closing the
namespace in between. So this has to do with when default arguments
are parsed for templates. I remember writing a comment about exactly
this in one of our other PRs, but I can't find it :-( The story of
that PR was that default arguments are really only parsed at the
point of _instantiation_ of the template -- but that would be clearly
too late here, unless we parsed the default arguments of _all_ the
declarations we have seen so far for a function, and made sure that
they match.

W.

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[philippe dot haution at mines-paris dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540



------- Additional Comments From philippe dot haution at mines-paris dot org  2003-07-17 08:38 -------
8.6.3/4 asserts that a default argument shall not be redefined by a later 
declaration, not even to the same value; so I am afraid checking that all 
declarations of default arguments have the same value wouldn't be enough here, 
the compiler should also check that there is only one definition of default 
arguments per translation unit.

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[bangerth at dealii dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540


bangerth at dealii dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4                         |---

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[bangerth at dealii dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540


bangerth at dealii dot org changed:

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


------- Additional Comments From bangerth at dealii dot org  2003-08-06 14:35 -------
*** Bug 11827 has been marked as a duplicate of this bug. ***

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[bangerth at dealii dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540



------- Additional Comments From bangerth at dealii dot org  2003-08-06 14:36 -------
PR 11827 has some more information, as well as a small patch by Jakub.
W.

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[jakub at gcc dot gnu dot org]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540


jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |3.3.2

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[dhazeghi at yahoo dot com]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540


dhazeghi at yahoo dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.3.2                       |---

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[jens dot maurer at gmx dot net]

------- Additional Comments From jens dot maurer at gmx dot net  2004-07-13 19:42 -------
This bug looks like a duplicate of bug 15339 to me.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540

[Bug c++/11540] Redefinition of default arguments allowed for template functions

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-07-13 20:13 -------
Yes, thanks for the tip.

*** This bug has been marked as a duplicate of 15339 ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=11540