__USE(3)

💅 __USE — the "bestie, I prom we used you" macro 💅

Hey bestie, welcome to __USE(3) from the Library Functions Manual! This is a little compile-time macro that tells your compiler "no fr, this variable is being used" so it stops side-eyeing you with warnings. Let's get into it ✨

---

🌸 NAME 🌸

__USE — a compile time macro that marks a variable as being used 💖

---

🎀 SYNOPSIS 🎀

#include <sys/cdefs.h>

void
__USE(x);

That's it. That's the whole vibe. 🦋

---

✨ DESCRIPTION ✨

Okay so the __USE macro is here to omit warnings produced by certain compilers when variables are being set but not used in a function. Like, the compiler is just trying to look out for you, but sometimes it's doing the most. 😭

There are cases where it's simpler to mark a variable as used, as opposed to ifdef-ing out its use. It's giving "there's a cleaner way, bestie":

#ifdef DEBUG_FOO
#define DPRINTF(a) printf a
#else
#define DPRINTF(a)

void
foo(void) {
        int var;

        var = getval();

        DPRINTF(("val is %d0, var));
}

In this case, ifdef-ing the code would make it:

void
foo(void) {
#ifdef DEBUG_FOO
        int var;

        var = getval();

        DPRINTF(("val is %d0, var));
#else
        (void)getval();
#endif
}

And that's just... not desirable, because it duplicates code. Not the move. 💀 With the __USE macro, you can write it like this instead:

void
foo(void) {
        int var;

        var = getval();

#ifdef DEBUG_FOO
        DPRINTF(("val is %d0, var));
#else
        __USE(var);
#endif
}

...without producing compiler warnings. Slay. 👑

Now, yes, it's simple to just write:

        (void)var;

But abstracting this into the macro allows for alternate implementations, as well as changing it to an empty implementation so that the liveness of the variable can be re-evaluated. Iconic flexibility, honestly. 🌈

---

🧚 IMPLEMENTATION NOTES 🧚

__USE is implemented as:

#define __USE(a)        ((void)(a))

Look at her. Minimalist. Understated. Ate. 💅

---

🔥 SEE ALSO 🔥

• cc(1)
• cdefs(3)

Go read those too, iykyk 🫶

---

⚠️ CAVEATS ⚠️

Bestie, listen to me. __USE should be used sparingly because it can cause valid warnings to be hidden. And we love valid warnings — they're literally just the compiler caring about you.

Also, use of this macro is non-portable. It's part of the implementation namespace and should only be used in NetBSD code. No sneaking it into other projects, periodt. 🚫

---

Okay bye bestie, stay warning-free and stay iconic 💜

Debian 🌸 October 17, 2013 🌸 this manual page is __USE(3) and she served ✨