如何修复 C 错误 'true undeclared'

问题：

你有类似这样的 C 代码

true_undeclared_example.c

bool mybool = true;

bool mybool = true;

但当你尝试编译它时，你看到类似这样的错误消息

true_undeclared_output.txt

main.c: In function ‘main’:
main.c:2:5: error: unknown type name ‘bool’; did you mean ‘_Bool’?
     bool mybool = true;
     ^~~~
     _Bool
main.c:2:19: error: ‘true’ undeclared (first use in this function)
     bool mybool = true;
                   ^~~~
main.c:2:19: note: each undeclared identifier is reported only once for each function it appears in

main.c: In function ‘main’:
main.c:2:5: error: unknown type name ‘bool’; did you mean ‘_Bool’?
     bool mybool = true;
     ^~~~
     _Bool
main.c:2:19: error: ‘true’ undeclared (first use in this function)
     bool mybool = true;
                   ^~~~
main.c:2:19: note: each undeclared identifier is reported only once for each function it appears in

解决方案

添加

include_stdbool.c

#include <stdbool.h>

#include <stdbool.h>

在错误发生的源文件顶部。

此错误的原因是 bool 不是 C 中的标准类型（如 int 或 char），而只在 stdbool.h 中。此外，true 和 false 在 stdbool.h 中声明。

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