pahole: Make sure the features string is NUL terminated

To address this compiler warning:

  /home/acme/git/pahole/pahole.c: In function ‘parse_btf_features’:
  /home/acme/git/pahole/pahole.c:1353:9: warning: ‘strncpy’ specified bound 1024 equals destination size [-Wstringop-truncation]
   1353 |         strncpy(f, features, sizeof(f));
        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

  $ gcc -v |& tail -1
  gcc version 13.2.1 20231205 (Red Hat 13.2.1-6) (GCC)
  $

When building in Release mode, for instance by using the buildcmd.sh
script.

Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Fixes: 7bc9b9975545ab53 ("pahole: Add --btf_features support")
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/pahole.c b/pahole.c
index 768a2feb..0e079ae1 100644
--- a/pahole.c
+++ b/pahole.c
@@ -1338,7 +1338,7 @@ static void show_supported_btf_features(FILE *output)
 static void parse_btf_features(const char *features, bool strict)
 {
 	char *saveptr = NULL, *s, *feature_name;
-	char f[BTF_MAX_FEATURE_STR];
+	char f[BTF_MAX_FEATURE_STR + 1];
 
 	init_btf_features();
 
@@ -1350,7 +1350,7 @@ static void parse_btf_features(const char *features, bool strict)
 		return;
 	}
 
-	strncpy(f, features, sizeof(f));
+	strncpy(f, features, BTF_MAX_FEATURE_STR)[BTF_MAX_FEATURE_STR] = '\0';
 	s = f;
 	while ((feature_name = strtok_r(s, ",", &saveptr)) != NULL) {
 		struct btf_feature *feature = find_btf_feature(feature_name);