This checks whether the format string is a literal on the calling function. As bonobo_debug_print() takes already a va_list, we specify the format on the functions that call it The second number, which is 0 here, should then be the argument index of the variadic argument Fixed warning with clang | ../../libbonobo-2.32.1/bonobo/bonobo-debug.c:58:32: error: format string is not a string literal [-Werror,-Wformat-nonliteral] | vfprintf (_bonobo_debug_file, fmt, args); | ^~~ | 1 error generated. Upstream-Status: Pending Signed-off-by: Khem Raj Index: libbonobo-2.32.1/bonobo/bonobo-debug.c =================================================================== --- libbonobo-2.32.1.orig/bonobo/bonobo-debug.c +++ libbonobo-2.32.1/bonobo/bonobo-debug.c @@ -47,6 +47,7 @@ bonobo_debug_init(void) _bonobo_debug_file = stderr; } +__attribute__((__format__ (printf, 2, 0))) void bonobo_debug_print (const char *name, char *fmt, ...) {