diff --git a/include/arch/bits_portable.h b/include/arch/bits_portable.h
index 2890a74cb43..d4496665e86 100644
--- a/include/arch/bits_portable.h
+++ b/include/arch/bits_portable.h
@@ -29,7 +29,7 @@
 
 static ALWAYS_INLINE unsigned int find_msb_set(u32_t op)
 {
-	if (!op) {
+	if (op == 0) {
 		return 0;
 	}
 
diff --git a/include/arch/x86/arch.h b/include/arch/x86/arch.h
index 21bbf470f72..e5d6e7711f1 100644
--- a/include/arch/x86/arch.h
+++ b/include/arch/x86/arch.h
@@ -444,7 +444,7 @@ static ALWAYS_INLINE unsigned int z_arch_irq_lock(void)
 
 static ALWAYS_INLINE void z_arch_irq_unlock(unsigned int key)
 {
-	if (!(key & 0x200)) {
+	if ((key & 0x200) == 0) {
 		return;
 	}
 
diff --git a/include/atomic.h b/include/atomic.h
index 510ffdfffde..1596d60e91c 100644
--- a/include/atomic.h
+++ b/include/atomic.h
@@ -12,6 +12,8 @@
 #include <stdbool.h>
 #include <toolchain.h>
 
+#include <zephyr/types.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -312,7 +314,7 @@ extern atomic_val_t atomic_nand(atomic_t *target, atomic_val_t value);
  */
 
 #define ATOMIC_BITS (sizeof(atomic_val_t) * 8)
-#define ATOMIC_MASK(bit) (1 << ((bit) & (ATOMIC_BITS - 1)))
+#define ATOMIC_MASK(bit) (1 << ((u32_t)(bit) & (ATOMIC_BITS - 1)))
 #define ATOMIC_ELEM(addr, bit) ((addr) + ((bit) / ATOMIC_BITS))
 
 /**
diff --git a/include/gpio.h b/include/gpio.h
index 4507f2e994a..0d7dabe07a7 100644
--- a/include/gpio.h
+++ b/include/gpio.h
@@ -165,7 +165,7 @@ static inline int z_impl_gpio_enable_callback(struct device *port,
 	const struct gpio_driver_api *api =
 		(const struct gpio_driver_api *)port->driver_api;
 
-	if (!api->enable_callback) {
+	if (api->enable_callback == NULL) {
 		return -ENOTSUP;
 	}
 
@@ -181,7 +181,7 @@ static inline int z_impl_gpio_disable_callback(struct device *port,
 	const struct gpio_driver_api *api =
 		(const struct gpio_driver_api *)port->driver_api;
 
-	if (!api->disable_callback) {
+	if (api->disable_callback == NULL) {
 		return -ENOTSUP;
 	}
 
@@ -268,7 +268,7 @@ static inline int gpio_add_callback(struct device *port,
 	const struct gpio_driver_api *api =
 		(const struct gpio_driver_api *)port->driver_api;
 
-	if (!api->manage_callback) {
+	if (api->manage_callback == NULL) {
 		return -ENOTSUP;
 	}
 
@@ -297,7 +297,7 @@ static inline int gpio_remove_callback(struct device *port,
 	const struct gpio_driver_api *api =
 		(const struct gpio_driver_api *)port->driver_api;
 
-	if (!api->manage_callback) {
+	if (api->manage_callback == NULL) {
 		return -ENOTSUP;
 	}
 
@@ -428,7 +428,7 @@ static inline int z_impl_gpio_get_pending_int(struct device *dev)
 	const struct gpio_driver_api *api =
 		(const struct gpio_driver_api *)dev->driver_api;
 
-	if (!api->get_pending_int) {
+	if (api->get_pending_int == NULL) {
 		return -ENOTSUP;
 	}
 
diff --git a/include/i2c.h b/include/i2c.h
index 2120b1c9580..1c1fa8004a1 100644
--- a/include/i2c.h
+++ b/include/i2c.h
@@ -284,7 +284,7 @@ static inline int z_impl_i2c_slave_register(struct device *dev,
 	const struct i2c_driver_api *api =
 		(const struct i2c_driver_api *)dev->driver_api;
 
-	if (!api->slave_register) {
+	if (api->slave_register == NULL) {
 		return -ENOTSUP;
 	}
 
@@ -315,7 +315,7 @@ static inline int z_impl_i2c_slave_unregister(struct device *dev,
 	const struct i2c_driver_api *api =
 		(const struct i2c_driver_api *)dev->driver_api;
 
-	if (!api->slave_unregister) {
+	if (api->slave_unregister == NULL) {
 		return -ENOTSUP;
 	}
 
diff --git a/include/logging/log_core.h b/include/logging/log_core.h
index 6a41c06668b..727181b3d89 100644
--- a/include/logging/log_core.h
+++ b/include/logging/log_core.h
@@ -219,13 +219,13 @@ extern "C" {
 				.source_id = _id			    \
 			};						    \
 									    \
-			if (BIT(_level) & LOG_FUNCTION_PREFIX_MASK) {	\
+			if ((BIT(_level) & LOG_FUNCTION_PREFIX_MASK) != 0) {\
 				__LOG_INTERNAL(src_level,		    \
 						Z_LOG_STR(__VA_ARGS__));	    \
 			} else {					    \
 				__LOG_INTERNAL(src_level, __VA_ARGS__);	    \
 			}						    \
-		} else if (0) {						    \
+		} else if (false) {					    \
 			/* Arguments checker present but never evaluated.*/ \
 			/* Placed here to ensure that __VA_ARGS__ are*/     \
 			/* evaluated once when log is enabled.*/	    \
diff --git a/include/misc/list_gen.h b/include/misc/list_gen.h
index 9cba9d4b0a9..e9cb41598a3 100644
--- a/include/misc/list_gen.h
+++ b/include/misc/list_gen.h
@@ -58,7 +58,7 @@
 	static inline bool						\
 	sys_ ## __lname ## _is_empty(sys_ ## __lname ## _t *list)	\
 	{								\
-		return (!sys_ ## __lname ## _peek_head(list));		\
+		return (sys_ ## __lname ## _peek_head(list) == NULL);	\
 	}
 
 #define Z_GENLIST_PEEK_NEXT_NO_CHECK(__lname, __nname)			    \
@@ -145,7 +145,7 @@
 				   sys_ ## __nname ## _t *prev,		\
 				   sys_ ## __nname ## _t *node)		\
 	{								\
-		if (!prev) {						\
+		if (prev == NULL) {					\
 			sys_ ## __lname ## _prepend(list, node);	\
 		} else if (!z_ ## __nname ## _next_peek(prev)) {	\
 			sys_ ## __lname ## _append(list, node);		\
@@ -187,7 +187,7 @@
 				   sys_ ## __nname ## _t *prev_node,	      \
 				   sys_ ## __nname ## _t *node)		      \
 	{								      \
-		if (!prev_node) {					      \
+		if (prev_node == NULL) {				      \
 			z_ ## __lname ## _head_set(list,		      \
 				z_ ## __nname ## _next_peek(node));	      \
 									      \
diff --git a/include/misc/util.h b/include/misc/util.h
index 73f50bd8a80..9110bac5b61 100644
--- a/include/misc/util.h
+++ b/include/misc/util.h
@@ -94,7 +94,7 @@ constexpr size_t ARRAY_SIZE(T(&)[N]) { return N; }
 #define MIN(a, b) (((a) < (b)) ? (a) : (b))
 #endif
 
-static inline int is_power_of_two(unsigned int x)
+static inline bool is_power_of_two(unsigned int x)
 {
 	return (x != 0) && !(x & (x - 1));
 }
diff --git a/include/rtc.h b/include/rtc.h
index 11aac3a5549..7d7196d485d 100644
--- a/include/rtc.h
+++ b/include/rtc.h
@@ -101,7 +101,7 @@ __deprecated static inline int rtc_set_config(struct device *dev,
 	err = counter_set_top_value(dev, cfg->alarm_val,
 				    rtc_counter_top_callback, cfg->cb_fn);
 
-	if (!err && cfg->alarm_enable) {
+	if (err == 0 && cfg->alarm_enable != 0) {
 		err = counter_start(dev);
 	}
 
diff --git a/include/sensor.h b/include/sensor.h
index d65a3df4396..972f84b5561 100644
--- a/include/sensor.h
+++ b/include/sensor.h
@@ -288,7 +288,7 @@ static inline int z_impl_sensor_attr_set(struct device *dev,
 {
 	const struct sensor_driver_api *api = dev->driver_api;
 
-	if (!api->attr_set) {
+	if (api->attr_set == NULL) {
 		return -ENOTSUP;
 	}
 
@@ -318,7 +318,7 @@ static inline int sensor_trigger_set(struct device *dev,
 {
 	const struct sensor_driver_api *api = dev->driver_api;
 
-	if (!api->trigger_set) {
+	if (api->trigger_set == NULL) {
 		return -ENOTSUP;
 	}
 
diff --git a/include/uart.h b/include/uart.h
index ac06a9cb827..c11517ccbf3 100644
--- a/include/uart.h
+++ b/include/uart.h
@@ -582,7 +582,7 @@ static inline int z_impl_uart_err_check(struct device *dev)
 	const struct uart_driver_api *api =
 		(const struct uart_driver_api *)dev->driver_api;
 
-	if (api->err_check) {
+	if (api->err_check != NULL) {
 		return api->err_check(dev);
 	}
 	return 0;
@@ -657,7 +657,7 @@ static inline int z_impl_uart_configure(struct device *dev,
 	const struct uart_driver_api *api =
 				(const struct uart_driver_api *)dev->driver_api;
 
-	if (api->configure) {
+	if (api->configure != NULL) {
 		return api->configure(dev, cfg);
 	}
 
@@ -684,7 +684,7 @@ static inline int z_impl_uart_config_get(struct device *dev,
 	const struct uart_driver_api *api =
 				(const struct uart_driver_api *)dev->driver_api;
 
-	if (api->config_get) {
+	if (api->config_get != NULL) {
 		return api->config_get(dev, cfg);
 	}