如何修复 C 错误 'errno undeclared'

问题：

你有类似这样的 C 代码

main.c

errno = EFAULT;

errno = EFAULT;

但当你尝试编译它时，你看到类似这样的错误消息

error_message.txt

main.c: In function ‘main’:
main.c:4:5: error: ‘errno’ undeclared (first use in this function)
     errno = EFAULT;
     ^~~~~
main.c:4:5: note: each undeclared identifier is reported only once for each function it appears in
main.c:4:13: error: ‘EFAULT’ undeclared (first use in this function)
     errno = EFAULT;

main.c: In function ‘main’:
main.c:4:5: error: ‘errno’ undeclared (first use in this function)
     errno = EFAULT;
     ^~~~~
main.c:4:5: note: each undeclared identifier is reported only once for each function it appears in
main.c:4:13: error: ‘EFAULT’ undeclared (first use in this function)
     errno = EFAULT;

解决方案

添加

errno_include.c

#include <errno.h>

#include <errno.h>

在错误发生的源文件顶部。这将包含 errno 变量和特定错误代码如 EFAULT。

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