如何修复 GCC 错误 'implicit declaration of function printf'

问题：

你有类似这样的 C 代码

main.c

printf("test");

printf("test");

但当你尝试编译它时，你看到类似这样的警告

compile_warning.txt

main.c: In function ‘main’:
main.c:2:5: warning: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration]
     printf("test");
     ^~~~~~
main.c:2:5: warning: incompatible implicit declaration of built-in function ‘printf’
main.c:2:5: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’

main.c: In function ‘main’:
main.c:2:5: warning: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration]
     printf("test");
     ^~~~~~
main.c:2:5: warning: incompatible implicit declaration of built-in function ‘printf’
main.c:2:5: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’

解决方案

添加

fix_stdio.c

#include <stdio.h>

#include <stdio.h>

在警告发生的源文件顶部。

注意此警告消息只是警告，如果你正确使用 printf，你的程序即使没有 #include <stdio.h> 也能工作。但是，不正确使用 printf 和类似函数会导致难以调试的错误，因此我建议在任何情况下都添加 #include <stdio.h>，即使没有它也能工作。

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