Re: deletion of mem alloated using placement new

From:
 carvalho.miguel@gmail.com
Newsgroups:
comp.lang.c++
Date:
Fri, 31 Aug 2007 08:50:27 -0700
Message-ID:
<1188575427.092348.82980@k79g2000hse.googlegroups.com>
On 31 Ago, 11:48, Gianni Mariani <gi3nos...@mariani.ws> wrote:

Anonymous wrote:

I am writing memory allocation class policies for a template class.

I have defined one allocated like this:

template <class T>
struct myMallocAllocator
{
    static T* Allocate()
    {
        void * ptr = calloc(1, sizeof(T));
        if (ptr)
            return new(ptr) T ;
        else
            return 0 ;


The C++ thing is to throw std::bad_alloc and not return 0.

    }

    static void DeAllocate(T *ptr)
    {
        if(ptr);
            ptr->~T() ;


if (ptr) {
     ptr->~T();
     free( static_cast<void*>(ptr) );

}

    }
};

Am i deallocating correctly?


whats with the destructor calling? when you delete a pointer the
destructor is automatically called.
also is perfect valid to delete a NULL pointer, so no need to check if
it exists.

also why use malloc/calloc and free? why not new/delete? i cant see a
valid reason in this example to not use the standard c++ allocate/
deallocate operators.
so simple, no need to complicate it:

template <class T>
class Allocator
{
    public:
        static T* Allocate()
        {
            return new T;
        }

        static void Deallocate( T* t )
        {
            delete t;
        }
};

class Test
{
    public:
        Test()
        {
            std::cout << "Test::Test()" << std::endl;
        }

        ~Test()
        {
            std::cout << "Test::~Test()" << std::endl;
        }
};

int main( int argc, char** argv )
{
    Test *t = Allocator<Test>::Allocate();
    Allocator<Test>::Deallocate( t );

    return 0;
}

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