Re: mix placement new with a standard delete

Goran <>
Fri, 25 Mar 2011 10:04:09 CST
On Mar 24, 2:58 pm, Mike Kelley <> wrote:

Is it legal to mix placement new with a standard delete operation?

I think so (compilers seem to agree), but should not be done. If you
overload new, you better have equivalent overload of delete. Consider:

class test
test() { if (problem) throw some_exception; }
void* operator new(size_t, void* p) { return p; }

void* p = getmem();
auto_ptr<test> ptest(new (p) test);

If "problem" indeed happens, there is no matching operator delete of
the correct type to possibly free memory. For that, "test" needs

 void operator delete(void* p, void*) { ::delete p; }

BTW, without that corresponding "delete", e.g. comeau warns:

Test::operator new(size_t, void *)" has
         no corresponding operator delete (to be called if an
exception is
         thrown during initialization of an allocated object)

Of course, you are required to match allocation/deallocation in your
new/delete overloads.


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