How does C++ free the memory when a constructor throws an exception and a custom new is used

Question

I see the following constructs:

• new X will free the memory if X constructor throws.

• operator new() can be

Answer 1

'placement new' is not an overloaded version of new, but one of the variants of operator new , and also one that cannot be overloaded.

See can see the list of new operators here along with a description on how overloading them works.

If a constructor throws an exception when using placement new the compiler knows what new operator was used and call placement delete.