core: silence gcc warning about unitialized variable

When compiled with -O2, the compiler is not happy about dynamic_user_pop() and
would warn about the output variables not being set. It does have a point:
we were doing a cast from ssize_t to int, and theoretically there could be
wraparound. So let's add an explicit check that the cast to int is fine.

[540/2509] Compiling C object src/core/libsystemd-core-256.so.p/dynamic-user.c.o
../src/core/dynamic-user.c: In function ‘dynamic_user_close.isra’:
../src/core/dynamic-user.c:580:9: warning: ‘uid’ may be used uninitialized [-Wmaybe-uninitialized]
  580 |         unlink_uid_lock(lock_fd, uid, d->name);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/core/dynamic-user.c:560:15: note: ‘uid’ was declared here
  560 |         uid_t uid;
      |               ^~~
../src/core/dynamic-user.c: In function ‘dynamic_user_realize’:
../src/core/dynamic-user.c:476:29: warning: ‘new_uid’ may be used uninitialized [-Wmaybe-uninitialized]
  476 |                         num = new_uid;
      |                         ~~~~^~~~~~~~~
../src/core/dynamic-user.c:398:23: note: ‘new_uid’ was declared here
  398 |                 uid_t new_uid;
      |                       ^~~~~~~

diff --git a/src/core/dynamic-user.c b/src/core/dynamic-user.c
index 24ed889b61ef5fa1bb0795ee0dec50e42a0df6f8..11de2ba82b1e95f71712cbee88d39855522620e0 100644 (file)
--- a/src/core/dynamic-user.c
+++ b/src/core/dynamic-user.c
@@ -336,8 +336,10 @@ static int dynamic_user_pop(DynamicUser *d, uid_t *ret_uid, int *ret_lock_fd) {
          * the lock on the socket taken. */
 
         k = receive_one_fd_iov(d->storage_socket[0], &iov, 1, MSG_DONTWAIT, &lock_fd);
-        if (k < 0)
+        if (k < 0) {
+                assert(errno_is_valid(-k));
                 return (int) k;
+        }
 
         *ret_uid = uid;
         *ret_lock_fd = lock_fd;