diff --git a/include/json_writer.h b/include/json_writer.h
index 9ab88e1d..0c8831c1 100644
--- a/include/json_writer.h
+++ b/include/json_writer.h
@@ -29,6 +29,7 @@ void jsonw_pretty(json_writer_t *self, bool on);
 void jsonw_name(json_writer_t *self, const char *name);
 
 /* Add value  */
+__attribute__((format(printf, 2, 3)))
 void jsonw_printf(json_writer_t *self, const char *fmt, ...);
 void jsonw_string(json_writer_t *self, const char *value);
 void jsonw_bool(json_writer_t *self, bool value);
@@ -59,8 +60,6 @@ void jsonw_luint_field(json_writer_t *self, const char *prop,
 			unsigned long int num);
 void jsonw_lluint_field(json_writer_t *self, const char *prop,
 			unsigned long long int num);
-void jsonw_float_field_fmt(json_writer_t *self, const char *prop,
-			   const char *fmt, double val);
 
 /* Collections */
 void jsonw_start_object(json_writer_t *self);
diff --git a/ip/iplink_can.c b/ip/iplink_can.c
index 587413da..c0deeb1f 100644
--- a/ip/iplink_can.c
+++ b/ip/iplink_can.c
@@ -316,11 +316,14 @@ static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 		struct can_bittiming *bt = RTA_DATA(tb[IFLA_CAN_BITTIMING]);
 
 		if (is_json_context()) {
+			json_writer_t *jw;
+
 			open_json_object("bittiming");
 			print_int(PRINT_ANY, "bitrate", NULL, bt->bitrate);
-			jsonw_float_field_fmt(get_json_writer(),
-					      "sample_point", "%.3f",
-					      (float) bt->sample_point / 1000.);
+			jw = get_json_writer();
+			jsonw_name(jw, "sample_point");
+			jsonw_printf(jw, "%.3f",
+				     (float) bt->sample_point / 1000);
 			print_int(PRINT_ANY, "tq", NULL, bt->tq);
 			print_int(PRINT_ANY, "prop_seg", NULL, bt->prop_seg);
 			print_int(PRINT_ANY, "phase_seg1",
@@ -415,12 +418,14 @@ static void can_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 			RTA_DATA(tb[IFLA_CAN_DATA_BITTIMING]);
 
 		if (is_json_context()) {
+			json_writer_t *jw;
+
 			open_json_object("data_bittiming");
 			print_int(PRINT_JSON, "bitrate", NULL, dbt->bitrate);
-			jsonw_float_field_fmt(get_json_writer(),
-					      "sample_point",
-					      "%.3f",
-					      (float) dbt->sample_point / 1000.);
+			jw = get_json_writer();
+			jsonw_name(jw, "sample_point");
+			jsonw_printf(jw, "%.3f",
+				     (float) dbt->sample_point / 1000.);
 			print_int(PRINT_JSON, "tq", NULL, dbt->tq);
 			print_int(PRINT_JSON, "prop_seg", NULL, dbt->prop_seg);
 			print_int(PRINT_JSON, "phase_seg1",
diff --git a/lib/color.c b/lib/color.c
index eaf69e74..e5406294 100644
--- a/lib/color.c
+++ b/lib/color.c
@@ -132,6 +132,7 @@ void set_color_palette(void)
 		is_dark_bg = 1;
 }
 
+__attribute__((format(printf, 3, 4)))
 int color_fprintf(FILE *fp, enum color_attr attr, const char *fmt, ...)
 {
 	int ret = 0;
diff --git a/lib/json_print.c b/lib/json_print.c
index 5dc41bfa..77902824 100644
--- a/lib/json_print.c
+++ b/lib/json_print.c
@@ -100,6 +100,7 @@ void close_json_array(enum output_type type, const char *str)
  * functions handling different types
  */
 #define _PRINT_FUNC(type_name, type)					\
+	__attribute__((format(printf, 4, 0)))				\
 	void print_color_##type_name(enum output_type t,		\
 				     enum color_attr color,		\
 				     const char *key,			\
diff --git a/lib/json_writer.c b/lib/json_writer.c
index aa9ce1c6..68890b34 100644
--- a/lib/json_writer.c
+++ b/lib/json_writer.c
@@ -152,6 +152,7 @@ void jsonw_name(json_writer_t *self, const char *name)
 		putc(' ', self->out);
 }
 
+__attribute__((format(printf, 2, 3)))
 void jsonw_printf(json_writer_t *self, const char *fmt, ...)
 {
 	va_list ap;
@@ -205,11 +206,6 @@ void jsonw_null(json_writer_t *self)
 	jsonw_printf(self, "null");
 }
 
-void jsonw_float_fmt(json_writer_t *self, const char *fmt, double num)
-{
-	jsonw_printf(self, fmt, num);
-}
-
 void jsonw_float(json_writer_t *self, double num)
 {
 	jsonw_printf(self, "%g", num);
@@ -274,15 +270,6 @@ void jsonw_float_field(json_writer_t *self, const char *prop, double val)
 	jsonw_float(self, val);
 }
 
-void jsonw_float_field_fmt(json_writer_t *self,
-			   const char *prop,
-			   const char *fmt,
-			   double val)
-{
-	jsonw_name(self, prop);
-	jsonw_float_fmt(self, fmt, val);
-}
-
 void jsonw_uint_field(json_writer_t *self, const char *prop, unsigned int num)
 {
 	jsonw_name(self, prop);
diff --git a/misc/ss.c b/misc/ss.c
index b2c634c8..f99b6874 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -977,6 +977,7 @@ static int buf_update(int len)
 }
 
 /* Append content to buffer as part of the current field */
+__attribute__((format(printf, 1, 2)))
 static void out(const char *fmt, ...)
 {
 	struct column *f = current_field;
@@ -1094,7 +1095,7 @@ static void print_header(void)
 {
 	while (!field_is_last(current_field)) {
 		if (!current_field->disabled)
-			out(current_field->header);
+			out("%s", current_field->header);
 		field_next();
 	}
 }
diff --git a/tc/m_ematch.c b/tc/m_ematch.c
index ace4b3dd..a524b520 100644
--- a/tc/m_ematch.c
+++ b/tc/m_ematch.c
@@ -277,6 +277,7 @@ static int flatten_tree(struct ematch *head, struct ematch *tree)
 	return count;
 }
 
+__attribute__((format(printf, 5, 6)))
 int em_parse_error(int err, struct bstr *args, struct bstr *carg,
 		   struct ematch_util *e, char *fmt, ...)
 {
diff --git a/tc/m_ematch.h b/tc/m_ematch.h
index ff02d7ac..356f2ede 100644
--- a/tc/m_ematch.h
+++ b/tc/m_ematch.h
@@ -102,6 +102,7 @@ static inline int parse_layer(const struct bstr *b)
 		return INT_MAX;
 }
 
+__attribute__((format(printf, 5, 6)))
 int em_parse_error(int err, struct bstr *args, struct bstr *carg,
 		   struct ematch_util *, char *fmt, ...);
 int print_ematch(FILE *, const struct rtattr *);