Can examples couldn't be compiled

show error as below:
/home/spy/workspace/Gitlab_source/ardupilot/modules/PX4Firmware/src/drivers/boards/rainpx-v2/rainpx_can.c:109:5: error: no previous prototype for ‘can_devinit’ [-Werror=missing-prototypes]
my configure is:
— a/nuttx-configs/rainpx-v2/nsh/appconfig
+++ b/nuttx-configs/rainpx-v2/nsh/appconfig
@@ -36,13 +36,13 @@

Path to example in apps/examples containing the user_start entry point

CONFIGURED_APPS += examples/nsh
+CONFIGURED_APPS += examples/can

The NSH application library

CONFIGURED_APPS += nshlib
CONFIGURED_APPS += system/readline

ifeq ($(CONFIG_CAN),y)
-#CONFIGURED_APPS += examples/can
endif

#ifeq ($(CONFIG_USBDEV),y)
diff --git a/nuttx-configs/rainpx-v2/nsh/defconfig b/nuttx-configs/rainpx-v2/nsh/defconfig
index 20f6990…1d07316 100644
— a/nuttx-configs/rainpx-v2/nsh/defconfig
+++ b/nuttx-configs/rainpx-v2/nsh/defconfig
@@ -211,7 +211,7 @@ CONFIG_STM32_ADC1=y

CONFIG_STM32_ADC2 is not set

CONFIG_STM32_ADC3 is not set

CONFIG_STM32_BKPSRAM=y
-# CONFIG_STM32_CAN1 is not set
+CONFIG_STM32_CAN1=y

CONFIG_STM32_CAN2 is not set

CONFIG_STM32_CCMDATARAM=y

CONFIG_STM32_CRC is not set

@@ -468,7 +468,7 @@ CONFIG_DEV_NULL=y

CONFIG_DEV_ZERO is not set

CONFIG_LOOP is not set

CONFIG_RAMDISK is not set

-# CONFIG_CAN is not set
+CONFIG_CAN=y

CONFIG_PWM is not set

CONFIG_I2C=y

CONFIG_I2C_SLAVE is not set

@@ -831,7 +831,7 @@ CONFIG_BUILTIN_PROXY_STACKSIZE=1024

Examples

CONFIG_EXAMPLES_BUTTONS is not set

-# CONFIG_EXAMPLES_CAN is not set
+CONFIG_EXAMPLES_CAN=y
CONFIG_EXAMPLES_CDCACM=y

CONFIG_EXAMPLES_COMPOSITE is not set

CONFIG_EXAMPLES_CXXTEST is not set

@@ -1067,3 +1067,4 @@ CONFIG_NSOCKET_DESCRIPTORS=0

setup for 2MByte flash part

CONFIG_STM32_FLASH_CONFIG_I=y
+CONFIG_CAN1_BAUD=1000000

software version: Copter-3.5.0-rc4

anybody can explain this?
thanks

@EShamaev please help me

I am not sure that this is Ardupilot related. Please provide more information on version you are trying to compile.