include: rearrange for standard use of extern "C" in various headers

Consistently place C++ use of extern "C" after all include directives,
within the negative branch of _ASMLANGUAGE if used.

The inclusion of the generated syscall files is placed outside the
extern "C" block as the generated file has its own extern "C" block.

Background from issue #17997:

Declarations that use C linkage should be placed within extern "C"
so the language linkage is correct when the header is included by
a C++ compiler.

Similarly #include directives should be outside the extern "C" to
ensure the language-specific default linkage is applied to any
declarations provided by the included header.

See: https://en.cppreference.com/w/cpp/language/language_linkage
Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>

include/device.h

@@ -596,9 +596,10 @@ static inline int device_pm_put_sync(struct device *dev) { return -ENOTSUP; }
  * @}
  */
 
-#include <syscalls/device.h>
-
 #ifdef __cplusplus
 }
 #endif
+
+#include <syscalls/device.h>
+
 #endif /* ZEPHYR_INCLUDE_DEVICE_H_ */

include/drivers/adc.h

@@ -412,8 +412,6 @@ static inline u16_t adc_ref_internal(struct device *dev)
 	return api->ref_internal;
 }
 
-#include <syscalls/adc.h>
-
 /**
  * @}
  */
@@ -422,4 +420,6 @@ static inline u16_t adc_ref_internal(struct device *dev)
 }
 #endif
 
+#include <syscalls/adc.h>
+
 #endif  /* ZEPHYR_INCLUDE_DRIVERS_ADC_H_ */

include/drivers/console/uart_console.h

@@ -9,12 +9,12 @@
 #ifndef ZEPHYR_INCLUDE_DRIVERS_CONSOLE_UART_CONSOLE_H_
 #define ZEPHYR_INCLUDE_DRIVERS_CONSOLE_UART_CONSOLE_H_
 
+#include <kernel.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include <kernel.h>
-
 /** @brief Register uart input processing
  *
  *  Input processing is started when string is typed in the console.

include/drivers/gpio.h

@@ -465,10 +465,10 @@ struct gpio_pin_config {
  * @}
  */
 
-#include <syscalls/gpio.h>
-
 #ifdef __cplusplus
 }
 #endif
 
+#include <syscalls/gpio.h>
+
 #endif /* ZEPHYR_INCLUDE_DRIVERS_GPIO_H_ */

include/drivers/i2s.h

@@ -516,14 +516,14 @@ static inline int z_impl_i2s_trigger(struct device *dev, enum i2s_dir dir,
 	return api->trigger(dev, dir, cmd);
 }
 
-#include <syscalls/i2s.h>
+/**
+ * @}
+ */
 
 #ifdef __cplusplus
 }
 #endif
 
-/**
+#include <syscalls/i2s.h>
- * @}
- */
 
 #endif /* ZEPHYR_INCLUDE_DRIVERS_I2S_H_ */

include/drivers/pwm.h

@@ -19,10 +19,6 @@
  * @{
  */
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #define PWM_ACCESS_BY_PIN	0
 #define PWM_ACCESS_ALL		1
 
@@ -31,6 +27,10 @@ extern "C" {
 #include <stddef.h>
 #include <device.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * @typedef pwm_pin_set_t
  * @brief Callback API upon setting the pin

include/drivers/sensor.h

@@ -555,14 +555,14 @@ static inline double sensor_value_to_double(struct sensor_value *val)
 	return (double)val->val1 + (double)val->val2 / 1000000;
 }
 
-#include <syscalls/sensor.h>
+/**
+ * @}
+ */
 
 #ifdef __cplusplus
 }
 #endif
 
-/**
+#include <syscalls/sensor.h>
- * @}
- */
 
 #endif /* ZEPHYR_INCLUDE_DRIVERS_SENSOR_H_ */

include/drivers/timer/system_timer.h

@@ -16,14 +16,14 @@
 #ifndef ZEPHYR_INCLUDE_DRIVERS_SYSTEM_TIMER_H_
 #define ZEPHYR_INCLUDE_DRIVERS_SYSTEM_TIMER_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <stdbool.h>
 #include <device.h>
 #include <stdbool.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * @brief Initialize system clock driver
  *

include/fs/fcb.h

@@ -7,10 +7,6 @@
 #ifndef ZEPHYR_INCLUDE_FS_FCB_H_
 #define ZEPHYR_INCLUDE_FS_FCB_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /*
  * Flash circular buffer.
  */
@@ -21,6 +17,10 @@ extern "C" {
 
 #include <kernel.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * @defgroup fcb Flash Circular Buffer (FCB)
  * @ingroup file_system_storage

include/net/can.h

@@ -13,15 +13,16 @@
 #ifndef ZEPHYR_INCLUDE_NET_CAN_H_
 #define ZEPHYR_INCLUDE_NET_CAN_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #include <zephyr/types.h>
 #include <net/net_ip.h>
 #include <net/net_if.h>
 #include <can.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
 /**
  * @brief IPv6 over CAN library
  * @defgroup net_can Network Core Library

include/ptp_clock.h

@@ -92,10 +92,10 @@ static inline int ptp_clock_rate_adjust(struct device *dev, float rate)
 	return api->rate_adjust(dev, rate);
 }
 
-#include <syscalls/ptp_clock.h>
-
 #ifdef __cplusplus
 }
 #endif
 
+#include <syscalls/ptp_clock.h>
+
 #endif /* ZEPHYR_INCLUDE_PTP_CLOCK_H_ */

include/storage/flash_map.h

@@ -21,10 +21,6 @@
  * @{
  */
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /**
  *
  * Provides abstraction of flash regions for type of use,
@@ -46,6 +42,10 @@ extern "C" {
 #include <stddef.h>
 #include <sys/types.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #define SOC_FLASH_0_ID 0	/** device_id for SoC flash memory driver   */
 #define SPI_FLASH_0_ID 1	/** device_id for external SPI flash driver */
 

include/sw_isr_table.h

@@ -14,14 +14,14 @@
 #ifndef ZEPHYR_INCLUDE_SW_ISR_TABLE_H_
 #define ZEPHYR_INCLUDE_SW_ISR_TABLE_H_
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 #if !defined(_ASMLANGUAGE)
 #include <zephyr/types.h>
 #include <toolchain.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*
  * Note the order: arg first, then ISR. This allows a table entry to be
  * loaded arg -> r0, isr -> r3 in _isr_wrapper with one ldmia instruction,
@@ -75,10 +75,10 @@ struct _isr_list {
 void z_isr_install(unsigned int irq, void (*routine)(void *), void *param);
 #endif
 
-#endif /* _ASMLANGUAGE */
-
 #ifdef __cplusplus
 }
 #endif
 
+#endif /* _ASMLANGUAGE */
+
 #endif /* ZEPHYR_INCLUDE_SW_ISR_TABLE_H_ */

include/sys/atomic.h

@@ -456,9 +456,6 @@ static inline void atomic_set_bit_to(atomic_t *target, int bit, bool val)
 	}
 }
 
-#ifdef CONFIG_ATOMIC_OPERATIONS_C
-#include <syscalls/atomic.h>
-#endif
 /**
  * @}
  */
@@ -467,4 +464,8 @@ static inline void atomic_set_bit_to(atomic_t *target, int bit, bool val)
 }
 #endif
 
+#ifdef CONFIG_ATOMIC_OPERATIONS_C
+#include <syscalls/atomic.h>
+#endif
+
 #endif /* ZEPHYR_INCLUDE_SYS_ATOMIC_H_ */

include/sys/sys_io.h

@@ -9,13 +9,13 @@
 #ifndef ZEPHYR_INCLUDE_SYS_SYS_IO_H_
 #define ZEPHYR_INCLUDE_SYS_SYS_IO_H_
 
+#include <zephyr/types.h>
+#include <stddef.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include <zephyr/types.h>
-#include <stddef.h>
-
 typedef u32_t io_port_t;
 typedef u32_t mm_reg_t;
 typedef uintptr_t mem_addr_t;

include/sys_clock.h

@@ -19,13 +19,13 @@
 #include <sys/util.h>
 #include <sys/dlist.h>
 
+#include <toolchain.h>
+#include <zephyr/types.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#include <toolchain.h>
-#include <zephyr/types.h>
-
 #ifdef CONFIG_TICKLESS_KERNEL
 extern int _sys_clock_always_on;
 extern void z_enable_sys_clock(void);