repart: silence bogus gcc warning

[2/3] Compiling C object systemd-repart.p/src_partition_repart.c.o
../src/partition/repart.c: In function ‘context_open_copy_block_paths’:
../src/partition/repart.c:5194:41: warning: ‘devno’ may be used uninitialized [-Wmaybe-uninitialized]
 5194 |                         source_fd = r = device_open_from_devnum(S_IFBLK, devno, O_RDONLY|O_CLOEXEC|O_NONBLOCK, &opened);
      |                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/partition/repart.c:5188:31: note: ‘devno’ was declared here
 5188 |                         dev_t devno;
      |                               ^~~~~

This is with gcc-13.0.1-0.2.fc38.x86_64, -O2. I'm pretty sure the code
is correct. I also tried adding some asserts where errno is used for the return
value, but that didn't help. I think resolve_copy_blocks_auto() is just too long
for gcc to understand.

diff --git a/src/partition/repart.c b/src/partition/repart.c
index 8e878dbd8b2f656da18afbc2e22ef87b0e090132..6ba48b528ec8b10d9c6195b402ba07c0075793d5 100644 (file)
--- a/src/partition/repart.c
+++ b/src/partition/repart.c
@@ -5183,11 +5183,12 @@ static int context_open_copy_block_paths(
                                                        "Copying from block device node is not permitted in --image=/--root= mode, refusing.");
 
                 } else if (p->copy_blocks_auto) {
-                        dev_t devno;
+                        dev_t devno = 0;  /* Fake initialization to appease gcc. */
 
                         r = resolve_copy_blocks_auto(p->type, p->copy_blocks_root, restrict_devno, &devno, &uuid);
                         if (r < 0)
                                 return r;
+                        assert(devno != 0);
 
                         source_fd = r = device_open_from_devnum(S_IFBLK, devno, O_RDONLY|O_CLOEXEC|O_NONBLOCK, &opened);
                         if (r < 0)