-#define DBG(fmt, args...) fprintf(stderr, fmt "\n", ## args)
-#define WARN(fmt, args...) fprintf(stderr, "usertrace: WARNING: " fmt "\n", ## args)
-#define ERR(fmt, args...) fprintf(stderr, "usertrace: ERROR: " fmt "\n", ## args)
+#define DBG(fmt, args...) fprintf(stderr, fmt "\n", ## args); fflush(stderr)
+#define WARN(fmt, args...) fprintf(stderr, "usertrace: WARNING: " fmt "\n", ## args); fflush(stderr)
+#define ERR(fmt, args...) fprintf(stderr, "usertrace: ERROR: " fmt "\n", ## args); fflush(stderr)
+#define BUG(fmt, args...) fprintf(stderr, "usertrace: BUG: " fmt "\n", ## args); fflush(stderr)