Question

I have a method

**int** create_object(Object* parent, char* name, int type, int start_block) {
  ...
  return ptr_to_object;
}

Inside the function ptr_to_object seems to be a 32-bits but then as soon as it gets out of it, it looks like its 64-bits.

Note: I cannot use c99, I know that intptr_t is part of c99.

What are your suggestions? Thanks!

Answer 1

If you’re dealing with pointers, either use a pointer return type, or “hide” it in an int-type defined by the standard to be large enough to support holding a pointer. Such a type can exist but is not guaranteed to exist (tmk):

C99 7.20.1.4 Integer types capable of holding object pointers

1. The following type designates a signed integer type with the property that any valid pointer to void can be converted to this type, then converted back to pointer to void, and the result will compare equal to the original pointer:

   intptr_t

   The following type designates an unsigned integer type with the property that any valid pointer to void can be converted to this type, then converted back to pointer to void, and the result will compare equal to the original pointer:

   uintptr_t

   These types are optional.

The keyword there is optional. Chance are likely it is defined on your platform of choice, but for legacy portability you’re probably better off either returning a void * or declaring a specialized “handle” to a typed or void pointer and returning that.

As always, I’m entirely interested in anyone that is working with a C99-compliant platform that chose not to expose some of the features presented as optional in the standard (like this one). If there is anyone out that with a <stdint.h> without intptr_t and/or uintptr_t I’m very curious. Please leave a comment if you work with such a toolchain.