Question

Consider the following C99 function:

void port_pin_set(const bool value, const uint8_t pin_mask)
{
    if (value) {
        PORT |= pin_mask;
    } else {
        PORT &= ~pin_mask;
    }
}

With PORT being a define, for example:

#define PORT (P1OUT)

Is there a way to redefine PORT so that:

• it is accepted as an lvalue,
• the function does not do anything.

What I want to do is to keep the function source as is, while compiling it to do nothing.

Edit: I am aware that using such an lvalue might not be the best solution. I am not looking for the best solution for this specific problem, I am interested in the language itself. This is a theoretical question, not a pragmatic one.

Answer 1

C99 has compound literals that can be used for such a task. Their syntax is a cast followed by an initializer:

#define PORT ((int){0})

should do it in your case, only that you might get some warnings about unused values or so.

Any decent compiler will optimize assignments to such compound literal out.