barrier: fix up constructor error handling

We cannot rely on "errno" to be non-zero on failure, if we perform
multiple glibc calls. That is, if the first eventfd() call fails, but the
second succeeds, we cleanup the barrier but return 0.

Fix this by always testing the return value immediately. This should also
fix all the coverity warnings.

src/shared/barrier.c

@@ -112,15 +112,24 @@
  * Returns: 0 on success, negative error code on failure.
  */
 int barrier_create(Barrier *b) {
+        _cleanup_(barrier_destroyp) Barrier *staging = b;
+        int r;
+
         assert(b);
 
-        if ((b->me = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK)) < 0 ||
-            (b->them = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK)) < 0 ||
-            pipe2(b->pipe, O_CLOEXEC | O_NONBLOCK) < 0) {
-                barrier_destroy(b);
+        b->me = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
+        if (b->me < 0)
                 return -errno;
-        }
 
+        b->them = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
+        if (b->them < 0)
+                return -errno;
+
+        r = pipe2(b->pipe, O_CLOEXEC | O_NONBLOCK);
+        if (r < 0)
+                return -errno;
+
+        staging = NULL;
         return 0;
 }
 

src/shared/barrier.h

@@ -62,6 +62,8 @@ struct Barrier {
 int barrier_create(Barrier *obj);
 void barrier_destroy(Barrier *b);
 
+DEFINE_TRIVIAL_CLEANUP_FUNC(Barrier*, barrier_destroy);
+
 void barrier_set_role(Barrier *b, unsigned int role);
 
 bool barrier_place(Barrier *b);