C - What does this line mean?

Question

I am trying to understand what the following line of the worst-ever-seen C code (from uboot project) mean:

rc = ((ulong (*)(bd_t *, int, char *[]))addr) (bd, --argc, &argv[1]);

What is it? A function call? Can it be more readable?

Thanks in advance for your help!

Answer 1

Yes, it's a function call.

It casts the value in addr to a function pointer which accepts (bd_t *, int, char *[]) as arguments and returns a ulong, and calls the function. It could be sugared into:

typedef ulong (*bd_function)(bd_t *bd, int argc, char *argv[]);

bd_function bdfunc = (bd_function) addr;

rc = bdfunc(bd, --argc, &argv[1]);

This might be overkill, to introduce a typedef if this only happens once, but I feel it helps a lot to be able to look at the function pointer's type separately.