bunzip: work around gcc13 warning

While provable that length[0] is always initialized (because symCount
cannot be zero), upcoming gcc13 fails to recognize this and warns about
the unconditional use of the value immediately following the loop.

See also https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106511.

Reported-by: Martin Liška <martin.liska@suse.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: 402195e56de0aacf97e05c80ed367d464ca6938b
master date: 2023-03-14 10:45:28 +0100

diff --git a/xen/common/bunzip2.c b/xen/common/bunzip2.c
index 2087cfbbedc850da646659195cb4678fa68cb1a1..5108e570ed5dc58d05f69d638212f9c1f1849b98 100644 (file)
--- a/xen/common/bunzip2.c
+++ b/xen/common/bunzip2.c
@@ -233,6 +233,11 @@ static int __init get_next_block(struct bunzip_data *bd)
                   becomes negative, so an unsigned inequality catches
                   it.) */
                t = get_bits(bd, 5)-1;
+               /* GCC 13 has apparently improved use-before-set detection, but
+                  it can't figure out that length[0] is always intialized by
+                  virtue of symCount always being positive when making it here.
+                  See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106511. */
+               length[0] = 0;
                for (i = 0; i < symCount; i++) {
                        for (;;) {
                                if (((unsigned)t) > (MAX_HUFCODE_BITS-1))