report sem value overflows in sem_post

this is not required by the standard, but it's nicer than corrupting
the state and rather inexpensive.

diff --git a/src/thread/sem_post.c b/src/thread/sem_post.c
index 148ab78..14a2dfe 100644 (file)
--- a/src/thread/sem_post.c
+++ b/src/thread/sem_post.c
@@ -7,6 +7,10 @@ int sem_post(sem_t *sem)
        do {
                val = sem->__val[0];
                waiters = sem->__val[1];
+               if (val == SEM_VALUE_MAX) {
+                       errno = EOVERFLOW;
+                       return -1;
+               }
        } while (a_cas(sem->__val, val, val+1+(val<0)) != val);
        if (val<0 || waiters) __wake(sem->__val, 1, 0);
        return 0;