warning: implicit declaration of function 'exti_init’ is invalid in C99

回答: 这个警告的意思是在C99标准中，函数'exti_init'的隐式声明是无效的。\[3\]在C语言中，函数的定义要出现在函数调用之前，否则会报错。如果在调用函数之前没有定义，就需要在调用之前进行函数的声明，然后再进行函数的定义。所以解决这个警告的方法是先声明函数，再调用函数，最后再定义函数。
#### 引用[.reference_title]
- *1* [warning: implicit declaration of function ‘gets‘ is invalid in C99 [-Wimplicit-function-...](https://blog.csdn.net/qq_50635297/article/details/128265518)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^control_2,239^v3^insert_chatgpt"}} ] [.reference_item]
- *2* [keil5 编译过程中出现“warning：implicit declaration of function ‘LED_Init ‘ is invalid in C99](https://blog.csdn.net/m0_54355842/article/details/113285623)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^control_2,239^v3^insert_chatgpt"}} ] [.reference_item]
- *3* [关于Warning：Implicit declaration of function “xxx” is invalid in C99警告！](https://blog.csdn.net/family20102010/article/details/126155338)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v91^control_2,239^v3^insert_chatgpt"}} ] [.reference_item]
[ .reference_list ]