int log_remove_callback(log_callback_fn fn, void *priv);
char *alloc_vprintf(const char *fmt, va_list ap);
-char *alloc_printf(const char *fmt, ...);
+char *alloc_printf(const char *fmt, ...)
+ __attribute__ ((format (PRINTF_ATTRIBUTE_FORMAT, 1, 2)));
extern int debug_level;