[xen stable-4.17] bunzip: work around gcc13 warning

[patchbot@xxxxxxx]

commit 7082d656ae9bcd26392caf72e50e0f7a61c8f285
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Mar 21 13:47:11 2023 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Mar 21 13:47:11 2023 +0100

    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@xxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 402195e56de0aacf97e05c80ed367d464ca6938b
    master date: 2023-03-14 10:45:28 +0100
---
 xen/common/bunzip2.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/xen/common/bunzip2.c b/xen/common/bunzip2.c
index 61b80aff1b..4466426941 100644
--- 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))
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.17