From 529ada21ff9e37a14fd02ab1fb9d58d71d7a0d9e Mon Sep 17 00:00:00 2001 From: Greg Kroah-Hartman Date: Thu, 31 Aug 2017 09:09:54 +0200 Subject: [PATCH] lz4: fix bogus gcc warning MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When building lz4 under gcc-7 we get the following bogus warning: CC [M] lib/lz4/lz4hc_compress.o lib/lz4/lz4hc_compress.c: In function ‘lz4hc_compress’: lib/lz4/lz4hc_compress.c:179:42: warning: ‘delta’ may be used uninitialized in this function [-Wmaybe-uninitialized] chaintable[(size_t)(ptr) & MAXD_MASK] = delta; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~ lib/lz4/lz4hc_compress.c:134:6: note: ‘delta’ was declared here u16 delta; ^~~~~ This doesn't show up in the 4.4-stable tree due to us turning off warnings like this. It also doesn't show up in newer kernel versions as this code was totally rewritten. So for now, to get the 4.9-stable tree to build with 0 warnings on x86 allmodconfig, let's just shut the compiler up by initializing the variable to 0, despite it not really doing anything. To be far, this code is crazy complex, so the fact that gcc can't determine if the variable is really used or not isn't that bad, I'd blame the code here instead of the compiler. Signed-off-by: Greg Kroah-Hartman --- lib/lz4/lz4hc_compress.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/lz4/lz4hc_compress.c b/lib/lz4/lz4hc_compress.c index f344f76..6b2e046 100644 --- a/lib/lz4/lz4hc_compress.c +++ b/lib/lz4/lz4hc_compress.c @@ -131,7 +131,7 @@ static inline int lz4hc_insertandfindbestmatch(struct lz4hc_data *hc4, #endif int nbattempts = MAX_NB_ATTEMPTS; size_t repl = 0, ml = 0; - u16 delta; + u16 delta = 0; /* HC4 match finder */ lz4hc_insert(hc4, ip); -- 2.7.4