代码

int main() {
    // 定义变量a，赋值为10
    int a = 10;
    // 定义变量b，赋值为20
    int b = 20;
    // 定义变量c，将a和b相加的结果赋值给c
    int c = a + b;
    // 输出c的值
    printf("%d", c);
    // 返回0，表示程序正常结束
    return 0;
}

问题：

vscode中使用code-runner插件允许c程序报错：

[Running] cd "d:\dev\c\study\" && gcc demo1.c -o demo1 && "d:\dev\c\study\"demo1
demo1.c: In function 'main':
demo1.c:9:5: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    9 |     printf("%d", c);
      |     ^~~~~~
demo1.c:1:1: note: include '<stdio.h>' or provide a declaration of 'printf'
  +++ |+#include <stdio.h>
    1 | int main() {
demo1.c:9:5: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
    9 |     printf("%d", c);
      |     ^~~~~~
demo1.c:9:5: note: include '<stdio.h>' or provide a declaration of 'printf'

[Done] exited with code=1 in 0.239 seconds

原因

未添加c头文件

#include <stdio.h>