libubox: add format string checking to ulog()

This offers an increased level of security, as the arguments will be
checked for validity against the format string at compile time. The
format attribute is supported by both GCC and Clang, so there shouldn't
be any portability issues.

Signed-off-by: Kristupas Savickas <savickas.kristupas@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/ulog.h b/ulog.h
index 4818b1a..46d3c77 100644
--- a/ulog.h
+++ b/ulog.h
@@ -32,7 +32,8 @@ void ulog_close(void);
 
 void ulog_threshold(int threshold);
 
-void ulog(int priority, const char *fmt, ...);
+void ulog(int priority, const char *fmt, ...)
+	__attribute__ ((format (printf, 2, 3)));
 
 #define ULOG_INFO(fmt, ...) ulog(LOG_INFO, fmt, ## __VA_ARGS__)
 #define ULOG_NOTE(fmt, ...) ulog(LOG_NOTICE, fmt, ## __VA_ARGS__)