How do I call the original "operator new" if I have overloaded it?

You can't access them because it isn't really overloading, it's replacement. When you define your own ::operator new, the old one goes away. That's pretty much that.

Essentially, you need to call malloc from a custom ::operator new. Not only that, but also follow the directions in 18.4.1.1/4 to properly handle errors:

Default behavior:

— Executes a loop: Within the loop, the function first attempts to allocate the requested storage. Whether the attempt involves a call to the Standard C library function malloc is unspecified.

— Returns a pointer to the allocated storage if the attempt is successful. Otherwise, if the last argument to set_new_handler() was a null pointer, throw bad_alloc.

— Otherwise, the function calls the current new_handler (18.4.2.2). If the called function returns, the loop repeats.

— The loop terminates when an attempt to allocate the requested storage is successful or when a called new_handler function does not return.