error: use of undeclared identifier 'my_function'

This error message means that the identifier 'my_function' has not been declared or defined before it is being used.

This can happen if you have not declared or defined the function in your code or if you have misspelled the function name when calling it.

To fix this error, you need to either declare or define the function before you use it, or correct the spelling of the function name if it is a typo.

相关问题

Build started: Project: template *** Using Compiler 'V6.19', folder: 'D:\Keil_v5\ARM\ARMCLANG\Bin' Build target 'Target 1' ../User/main.c(2): error: 'lora.h' file not found #include "lora.h" ^~~~~~~~ 1 error generated. compiling main.c... LoRa.c(8): error: use of undeclared identifier 'RCU_AF' rcu_periph_clock_enable(RCU_AF); ^ LoRa.c(9): error: call to undeclared function 'gpio_init'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] gpio_init(LORA_UART_GPIO, GPIO_MODE_AF_PP, GPIO_OSPEED_50MHZ, LORA_UART_GPIO_PIN_TX); ^ LoRa.c(9): error: use of undeclared identifier 'GPIO_MODE_AF_PP' gpio_init(LORA_UART_GPIO, GPIO_MODE_AF_PP, GPIO_OSPEED_50MHZ, LORA_UART_GPIO_PIN_TX); ^ LoRa.c(10): error: use of undeclared identifier 'GPIO_MODE_IN_FLOATING' gpio_init(LORA_UART_GPIO, GPIO_MODE_IN_FLOATING, GPIO_OSPEED_50MHZ, LORA_UART_GPIO_PIN_RX); ^ LoRa.c(23): error: use of undeclared identifier 'GPIO_MODE_IPU' gpio_init(LORA_AUX_GPIO, GPIO_MODE_IPU, GPIO_OSPEED_50MHZ, LORA_AUX_GPIO_PIN); ^ 5 errors generated. compiling LoRa.c... Usart.c(8): error: use of undeclared identifier 'RCU_AF' rcu_periph_clock_enable(RCU_AF); ^ Usart.c(9): error: call to undeclared function 'gpio_init'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration] gpio_init(USART_UART_GPIO, GPIO_MODE_AF_PP, GPIO_OSPEED_50MHZ, USART_UART_GPIO_PIN_TX); ^ Usart.c(9): error: use of undeclared identifier 'GPIO_MODE_AF_PP' gpio_init(USART_UART_GPIO, GPIO_MODE_AF_PP, GPIO_OSPEED_50MHZ, USART_UART_GPIO_PIN_TX); ^ Usart.c(10): error: use of undeclared identifier 'GPIO_MODE_IN_FLOATING' gpio_init(USART_UART_GPIO, GPIO_MODE_IN_FLOATING, GPIO_OSPEED_50MHZ, USART_UART_GPIO_PIN_RX); ^ 4 errors generated. compiling Usart.c... ".\Objects\template.axf" - 10 Error(s), 0 Warning(s). Target not created. Build Time Elapsed: 00:00:01

很抱歉，看起来编译器无法找到 `lora.h` 头文件。请确保你已经将 `lora.h` 和 `lora.c` 文件正确地放置在项目文件夹中，并确保编译器能够找到这些文件。请检查以下几点：

1. 确保 `lora.h` 和 `lora.c` 文件与主程序文件在同一个文件夹下。
2. 确保在主程序文件中正确地包含了 `lora.h` 头文件：`#include "lora.h"`。
3. 确保你的项目设置中包含了正确的路径，以便编译器能够找到这些文件。

如果问题仍然存在，请提供更多关于你的项目结构和编译器设置的信息，以便我能够提供更详细的帮助。

error: use of undeclared identifier 'localtime_s'

This error message indicates that the function "localtime_s" has not been declared, meaning that the compiler does not recognize or have access to this function. This could be due to a missing header file or library that contains the declaration for this function.

To resolve this error, you may need to include the appropriate header file or library that declares the "localtime_s" function. In C++, you can include the <ctime> header file to access time-related functions. Additionally, you may need to check that your compiler supports this function, as it may not be available on all platforms or versions of C++.