LLVM平行宇宙计划问题修复文档：call to undeclared function问题 · Pull Request !36 · openEuler/compiler-docs

# 1、问题现象

`[  705s] test/regress.c:3689:12: error: call to undeclared function 'event_base_start_iocp_'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]`

`[  705s] test/regress.c:3691:2: error: call to undeclared function 'event_base_stop_iocp_'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]`

# 2、问题定位

## 2.1、问题定位分析

[add-testcases-for-event.c-apis.patch](https://gitee.com/src-openeuler/libevent/blob/6fd712438bafd9eafdb3cf3b3e9d66913378b2a3/add-testcases-for-event.c-apis.patch)是对regress.c的patch，该patch中调用了函数`event_base_start_iocp_`与`event_base_stop_iocp_`但忘记了#include其所在的头文件"iocp-internal.h"

## 2.2 gcc与clang对于调用未声明函数的差异处理

对于调用未声明的函数，clang对于语法要求更加严格，会直接报错，而gcc则较为宽松，仅仅对其进行警告，并询问是否是要调用已包含的其他名称相近的函数

![gcc遇到未声明函数时的表现](https://foruda.gitee.com/images/1725034630272359183/577103f3_13034847.png "屏幕截图")

## 2.3、问题总结及根因确认

[add-testcases-for-event.c-apis.patch](https://gitee.com/src-openeuler/libevent/blob/6fd712438bafd9eafdb3cf3b3e9d66913378b2a3/add-testcases-for-event.c-apis.patch)是对regress.c的patch，该patch中调用了函数`event_base_start_iocp_`与`event_base_stop_iocp_`但忘记了#include其所在的头文件"iocp-internal.h"，gcc对于调用未声明函数会进行模糊处理，仅仅warning，而clang会报error

# 3、修改建议

补充打一个patch，在regress.c中#include "iocp-internal.h"，参考：[Fix function undeclared,incompatible pointer and parameter lack in &apos;add-testcases-for-event.c-apis.patch&apos;,support clang build · Pull Request !74 · src-openEuler/libevent - Gitee.com](https://gitee.com/src-openeuler/libevent/pulls/74)

类型	指派人员	状态
审查	openeuler-ci-bot	进行中 (0/1人)
测试	openeuler-ci-bot	进行中 (0/1人)

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