Re: compile time error due to changes in stl_list.h code

From:
 James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 19 Jul 2007 07:42:27 -0000
Message-ID:
<1184830947.660061.206680@z24g2000prh.googlegroups.com>
fimarn wrote:

I am trying to get rid of compile time error that I am getting
only in RHEL5 (not in RHEL4) apparently due to the changes in
the stl_list.h file. The error that I am getting is coming
from the following code that attempts to remove an item from
the list:


    [...]

========================
The allocator is declared as :

template<class T>
class SharedMemAlloc {

public:
    typedef size_t size_type;
    typedef ptrdiff_t difference_type;
    typedef T *pointer;
    typedef const T *const_pointer;
    typedef T& reference;
    typedef const T& const_reference;
    typedef T value_type;

    template <class _T> struct rebind {
      typedef SharedMemAlloc<_T> other;
    };

      static pointer allocate(size_type n)
    {
      return (pointer)SharedMemObj::allocate(n);
    }
    static void deallocate(void* p, size_type n)
    {
      SharedMemObj::deallocate(p, n);
    }

    void construct(pointer p, const T&val) {new (p) T(val); }
    void destroy(pointer p) {p->~T(); }
};


You're missing the conversion constructor. In the standard
allocator, it's a:

    template< typename U > allocator( allocator< U > const& ) ;

but if I understand the requirements correctly, all that is
required is that:

    Allocator< T > a( b ) ;

is legal, where b has a type Allocator< U >, with U different
from T. (So a conversion operator or an explicit constructor
would be legal. But I'd follow the model of the standard
allocator; I'd guess that very few, if any, implementations are
tested with anything really exotic.)

PS: I've not tried to test with this added to your allocator,
but it looks like a likely cause. And did you compile with
"-D_GLIBCXX_CONCEPT_CHECKS -D_GLIBCXX_DEBUG
-D_GLIBCXX_DEBUG_PEDANTIC"? I have no idea if this would help,
but I rather think that if you didn't get an error at the first
attempt to instantiate the template (i.e. when you use it as a
base class, in the header), the people at g++ would probably
consider this an error, and try to fix it in a future release.

--
James Kanze (GABI Software) email:james.kanze@gmail.com
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