c_wait
{"+=wait", c_wait},
int c_wait(char **);
wait = atomic_load_int(&c->c_wait);
wait = atomic_load_int(&c->c_wait);
atomic_store_int(&c->c_wait, 1);
atomic_store_int(&c->c_wait, 0);
unsigned int c_wait; /* [a] initialized and waiting */
#define COND_INITIALIZER() { .c_wait = 1 }