al_wait_cond(3)

💅 al_wait_cond(3) 💅

okay bestie, this is the Library Functions Manual page for al_wait_cond — yes, the Allegro 5 API one. Buckle up, because condition variables are giving very “wait for the signal” main character energy. ✨

🌸 NAME 🌸

al_wait_cond — Allegro 5 API

🦋 SYNOPSIS 🦋

#include <allegro5/allegro.h>

void al_wait_cond(ALLEGRO_COND *cond, ALLEGRO_MUTEX *mutex)

🎀 DESCRIPTION 🎀

Okay so picture this: when you enter this function, mutex must already be locked by the calling thread. No sneaky “I’ll lock it later” behavior, bestie. Once you’re in, al_wait_cond will atomically release mutex and block on cond. It comes back when cond is “signalled”, and it acquires the lock on the mutex in the process. The “atomically” part is doing a lot of work there — do not skip it. 💅

Here’s the proper-use example, verbatim:

al_lock_mutex(mutex);
while (something_not_true) {
   al_wait_cond(cond, mutex);
}
do_something();
al_unlock_mutex(mutex);

The recipe is this: the mutex should be locked before checking the condition, and the condition should be rechecked when al_wait_cond(3) returns. Why? Because al_wait_cond(3) can return for other reasons than the condition becoming true — e.g. the process was signalled. 💀 Rude, but real.

Also, if multiple threads are blocked on the condition variable, the condition may no longer be true by the time the second and later threads are unblocked. So yeah, group-chat rules apply: check again when you wake up. And remember not to unlock the mutex prematurely. That’s the plot twist we are avoiding, fr fr.

🚨 technical caveat, keep it close: al_wait_cond(3) can return for reasons other than the condition becoming true, like the process being signalled. Recheck the condition, and do not unlock that mutex early.

🌈 SEE ALSO 🌈

• al_wait_cond_until(3)
• al_broadcast_cond(3)
• al_signal_cond(3)

---

mwah 💋 that’s the page. Source/version: Allegro reference manual, for the page al_wait_cond(3). Date: there isn’t one listed on this page, so no fake date energy from me. 🫶