Question

I’m just wondering whether this is “good” code for a C89 program.

obj_ptr = (obj*) (ptr1 || ptr2);

Essentially what it does (atleast in GCC on my computer) is set obj_ptr as ptr1 if ptr1 != NULL and ptr2 otherwise.

I’ve looked around and I can’t see whether this is proper, but judging by the fact that the || operator has to convert the pointers to integers and then I have to cast them back is a hint of bad style.

If this is bad style or unportable, and is there a better and (hopefully) equally as terse solution?

EDIT: My primary concern whether the code I have written is portable and doesn’t rely on undefined behavior.

I may have found a better way which is portable and which I think is “good style” (unless you don’t like assignment in if statements).

if(!(obj_ptr = ptr1))
    obj_ptr = ptr2;

Answer 1

No, what it does is set obj_ptr to 1 if either ptr1 is not NULL or ptr2 is not NULL, and 0 otherwise. You need to use the ternary operator:

obj_ptr = ptr1 ? ptr1 : ptr2;