Re: why isn't there a placement delete syntax

benben <benhonghatgmaildotcom@nospam.invalid>
27 Sep 2006 09:18:23 -0400
<451a6073$0$23783$> wrote:


I have created an interface with placement new that uses a Heap
reference that supplies Alloc/Free functionality. The compiler forces
the definition of a placement delete. But there is no syntax that I
can find to invoke the placement delete!

struct Object {
    static void* operator new (Heap&, size_t);
    static void operator delete (Heap&, void*);

class MyObj : public Object {

main {
    Heap heap;
    MyObj* p = new (heap) MyObj(); // works!
    delete (heap) p; // illlegal!

Can anyone explain how to delete these objects. I.e. why doesn't the
obvious analagous invocation of delete work using placement syntax.
What do I do?

If your question is "how do I achieve what a placement delete would have
done?", then the answer will be: just call the destructor:


But if your question is "why, then, there is not a placement delete that
does exactly that?", then the answer would be long list arguments for
and against the topic.

Maybe you can think that a delete is always associated with memory
reclamation; but then why is there a placement new there that doesn't by
itself do any memory allocation? I don't know. The language ain't
perfect, I guess.

There are workarounds, of course. When you are allocating a single
object on your own heap, bury the placement new in some function so at
least you have a symmetry.

If you are allocating for a number of objects of the same type, you can
write yourself an allocator and use the standard containers.



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