fix -Werror build: logging.c: always use literal with snprintf

A recent commit added an snprintf that passes a pointer to a literal directly
to snprintf. Since passing pointers to printf formats is a vulnerability in
case user supplied data may be passed in the format, modern compilers warn
against that, which breaks our -Werror builds. Even though this is just a
pointer to a literal, it needs to be an actual literal to make compilers happy.

Use printf("%s", c) instead of printf(c).

Note that our current build slave's gcc does not enforce that yet, while newer
compilers do.

  logging.c:338:4: warning: format not a string literal and no format arguments [-Wformat-security]
       ret = snprintf(buf + offset, rem, c_subsys);

Change-Id: Ifa4eb8a9fab66dcd987986065351b4a06421f1ec

1 files changed, 1 insertions, 1 deletions

diff --git a/src/logging.c b/src/logging.c
index a6aa7eba..9b37bf53 100644
--- a/src/logging.c
+++ b/src/logging.c
@@ -335,7 +335,7 @@ static void _output(struct log_target *target, unsigned int subsys,
 	if (target->use_color) {
 		c_subsys = color(subsys);
 		if (c_subsys) {
-			ret = snprintf(buf + offset, rem, c_subsys);
+			ret = snprintf(buf + offset, rem, "%s", c_subsys);
 			if (ret < 0)
 				goto err;
 			OSMO_SNPRINTF_RET(ret, rem, offset, len);