private operator delete [duplicate]

Answer 1

• Seems, you are right about the first example.

Second and third examples deal with POD type. And there initialization differences play role.

• In the second example your structure left uninitialized. No problem appear.

• In opposite, in third example structure does initialize, so you get first case.

Edit:

Then, operator new itself can throw an exception. Standard (c++11 darft says):

If the new expression terminates by throwing an exception, it may release storage by calling a deallocation function (3.7.4.2). If the allocated type is a non-array type, the allocation function’s name is operator new and the deallocation function’s name is operator delete.

It's bit unclear, what authors wanted to express saying it may release storage. It seems to be implementation defined, if it is released.

Anyway, you can try using not-throwing new version:

void *operator new (size_t size, std::nothrow_t) throw() {
    return malloc(size);
}

Answer 2

Compiler creating constructor code which involves operators new and delete too in case if your constructor code throws an exception. So, using new automatically creates usage of delete.

In 2nd example compiler knows you using default constructor which never throws(my guess)..

Different compilers work different ways cus they are different (captain) and have different optimization capabilities and tricks to create code