原因:C语言的头文件不够
错误代码:未导入#include<stdlib.h>报错
#include <stdio.h>
#define R 1
int main()
{
float c,r,s;
c = 2;
#if R
r = 3.14*c*c;
printf("area of round is: %f\n",r);
#else
printf("byebye");
#endif
return 0;
}
~