[Bug libstdc++/16021] New: Tests for container swap specialisations FAIL in debug mode

[Bug libstdc++/16021] New: Tests for container swap specialisations FAIL in debug mode

[redi at gcc dot gnu dot org]

All testsuite/23_containers/*/modifiers/swap.cc files FAIL to compile
when _GLIBCXX_DEBUG is defined.

The following code is adapted from the testsuite:

    #define _GLIBCXX_DEBUG
    #include <vector>

    struct T { int i; };

    int swap_calls;

    namespace std
    {
      template<>
        void
        vector<T, allocator<T> >::swap(vector<T, allocator<T> >&)
        { ++swap_calls; }
    }

    // Should use vector specialization for swap.
    int main()
    {
      std::vector<T> A;
      std::vector<T> B;
      swap_calls = 0;
      std::swap(A, B);
      return swap_calls;
    }

Compiling this gives:

swap.cc:12: error: `allocator' was not declared in this scope
swap.cc:12: error: template argument 2 is invalid
swap.cc:12: error: variable or field `swap' declared void
swap.cc:12: error: `int __gnu_debug_def::vector<T, std::allocator<T> >::swap' is
 not a static member of `class __gnu_debug_def::vector<T, std::allocator<T> >'
swap.cc:12: error: expected primary-expression before ')' token
swap.cc:13: error: expected `;' before '{' token

The same error happens for all containers on 3.4 and mainline.

The diagnostic is confusing, it first says allocator is not found, then
identifies it as std::allocator in another diagnostic that seems to think
the member function is static.

A solution is to qualify allocator as std::allocator, but this shouldn't
be necessary because _GLIBCXX_DEBUG shouldn't change the meaning of any
conforming program.

I *think* what might be happening is that in debug mode the "std"
namespace is really "__gnu_debug" and the (non-debug) standard library
is really in "_GLIBCXX_STD". This means that the unqualified name
"allocator" looks up in __gnu_debug and the global namespace, and so
doesn't find "_GLIBCXX_STD::allocator". But I don't think I've got that
quite right.

-- 
           Summary: Tests for container swap specialisations FAIL in debug
                    mode
           Product: gcc
           Version: 3.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: redi at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug libstdc++/16021] Tests for container swap specialisations FAIL in debug mode

[redi at gcc dot gnu dot org]

------- Additional Comments From redi at gcc dot gnu dot org  2004-06-17 02:04 -------
I configured with concept-checks and PCH enabled

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug libstdc++/16021] Tests for container swap specialisations FAIL in debug mode

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-06-28 19:52 -------
I would argue that your code is in fact invalid, since you may not 
redefine members of namespace std. That being said, we should still 
make an attempt to get it working, or at least get the error messages 
to reflect what we mean. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug libstdc++/16021] Tests for container swap specialisations FAIL in debug mode

[redi at gcc dot gnu dot org]

------- Additional Comments From redi at gcc dot gnu dot org  2004-06-30 14:39 -------
Wolfgang, isn't this a specialisation of std::vector<T>::swap() (where T is a
user-defined type, not a template parameter) and therefore legal?

If it's illegal then there are lots of libstdc++ testsuite files that need fixing,
since my code was adapted from the testsuite and the code works fine in non-debug
mode. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug libstdc++/16021] Tests for container swap specialisations FAIL in debug mode

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-06-30 15:07 -------
I think the compiler should accept it, but adding anything to namespace std:: 
gets you on thin ice. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug libstdc++/16021] Tests for container swap specialisations FAIL in debug mode

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-06-30 17:29 -------
Wolfgang, the standard explicitally says that the only thing you are allowed to 
define in namespace std are specializations of standard templates. Everything 
else brings you into undefined behaviour, but this very thing is allowed and 
should work also in debug mode.

This is just another bug with strong using, I thikn it's a dup of whatever bug 
is left around about this.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug libstdc++/16021] Tests for container swap specialisations FAIL in debug mode

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-06-30 17:32 -------
Thanks, Giovanni, for the explanation. 
 
I thought about the strong using thingy as well, but then I was under 
the impression that it had been backed out of the compiler. We should 
try to come up with a smaller example, though I won't have the time to 
do so today. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug c++/16021] Tests for container swap specialisations FAIL in debug mode

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-06-30 17:49 -------
Hm, I _had_ to do it: 
----------------- 
namespace NS {} 
 
namespace std { 
  using namespace NS __attribute__ ((strong)); 
  class A{}; 
} 
 
namespace NS { 
  template<typename _Tp, typename _A = std::A> 
  class X { 
    void swap (X&); 
  }; 
} 
 
struct T {}; 
 
namespace std { 
  template<> 
  void X<T, A>::swap(X<T, A>&) {} 
} 
------------------- 
 
g/x> /home/bangerth/bin/gcc-3.4-pre/bin/c++ -c x.cc 
x.cc:19: error: `A' was not declared in this scope 
x.cc:19: error: template argument 2 is invalid 
x.cc:19: error: ISO C++ forbids declaration of `parameter' with no type 
x.cc:19: error: no member function `swap' declared in `NS::X<T, std::A>' 
x.cc:19: error: invalid function declaration 
 
That's of course bogus: 'A' _is_ declared in this scope, since it's a class 
inside namespace std, which we are presently in. 
 
The code is extracted from debug mode libstdc++, in which NS is the namespace 
in which the debug version of the containers are declared. If we want user 
programs to be able to compile with both debug and non-debug mode, we need 
to be able to allow specializations of NS::X members in namespace std, as 
shown in the example. Thus, the code should really compile. 
 
W. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|libstdc++                   |c++
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-06-30 17:49:04
               date|                            |
   Target Milestone|---                         |3.4.2
            Version|3.5.0                       |3.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug c++/16021] Tests for container swap specialisations FAIL in debug mode

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-08-02 18:52 -------
Assigned to Jason, as the inventor of "strong using".

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jason at redhat dot com
                   |dot org                     |
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug c++/16021] Tests for container swap specialisations FAIL in debug mode

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-08-29 18:51 -------
Postponed until GCC 3.4.3.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.2                       |3.4.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug c++/16021] Tests for container swap specialisations FAIL in debug mode

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-11-01 00:45 -------
Postponed until GCC 3.4.4.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.3                       |3.4.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug c++/16021] Tests for container swap specialisations FAIL in debug mode

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-02-12 21:00 -------
*** Bug 19550 has been marked as a duplicate of this bug. ***

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021

[Bug c++/16021] Tests for container swap specialisations FAIL in debug mode

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.4                       |3.4.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=16021