Re: libstdc++ of g++ 3.4.x: std::swap and std::auto_ptr causes compilationerrors

[Vinzenz Feenstra <evilissimo at web dot de>]

Paolo Carlini wrote:

> Vinzenz Feenstra wrote:
>
> > I had no problems with 3.3.x and 3.2.x, other versions I didn't test, 
> > but in my opinion it is strange.
>
>
> If true, would be definitely strange, since AFAIK, nothing changed in 
> this area recently.
>
> Can you send over a short snippet that now leads (correctly) to 
> compilation errors and didn't earlier?
>
> Thanks,
> Paolo.

Ok

I mentioned the problem while compiling OpenC++ and OpenC++ Core there 
is a file called MetacompilerConfiguration.h which uses auto_ptr and swap
but I made an other example which works with 3.3 and don't work with 3.4

// Example:
#include <memory>
#include <algorithm>
#include <iostream>

class TestClass
{
   int value;
 public:
    TestClass(int val_):value(val_){}
   ~TestClass(){}
    void Print(){ std::cout << "My Value is: " << value << std::endl;}
};


int main()
{

 std::auto_ptr<TestClass> A(new TestClass(0));
 std::auto_ptr<TestClass> B(new TestClass(1));

 A->Print();
 B->Print();

 std::cout << "Swapping A and B " << std::endl;

 std::swap(A ,B);

 A->Print();
 B->Print();

 return 0;
}
// Example ends


I had a view on bits/stl_algobase.h of 3.3 and 3.4 this is the 
difference of them:

std::swap of 3.3:

 template<typename _Tp>
   inline void
   swap(_Tp& __a, _Tp& __b)
   {
     // concept requirements
     __glibcpp_function_requires(_SGIAssignableConcept<_Tp>)
    
     _Tp __tmp = __a;
     __a = __b;
     __b = __tmp;
   }

std::swap of 3.4
 template<typename _Tp>
   inline void
   swap(_Tp& __a, _Tp& __b)
   {
     // concept requirements
     __glibcpp_function_requires(_SGIAssignableConcept<_Tp>)
    
     const _Tp __tmp = __a; // <-- this is the problem in my opinion
     __a = __b;
     __b = __tmp;
   }


BR

Vinzenz