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

From:

fimarn <fimarn@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 19 Jul 2007 18:53:01 -0000

Message-ID:

<1184871181.184187.122800@w3g2000hsg.googlegroups.com>

On Jul 19, 3:42 am, James Kanze <james.ka...@gmail.com> wrote:

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.ka...@gmail.com
Conseils en informatique orient=E9e objet/
                   Beratung in objektorientierter Datenverarbeitung
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I am not sure if I understand your suggestion. My allocators name is
SharedMemAlloc, so do I do the conversion that you suggested:

Allocator< T > a( b ) ;

I guess I need to make sure that my allocator handles not only (void
*) argument, but also std::_List_node<void* > >. I do not know how you
write it in C++.

Thanks for your help.