c - 使用strcpy时出错

Question

这个问题已经有答案了:

What header should I include for memcpy and realloc? (2 个回答)

warning: incompatible implicit declaration of built-in function 'strlen' and 'strcpy' [duplicate] (1 个回答)

已关闭 5 年前。

#include<stdio.h>
struct stud
{
  char name[20];
  int mark;
  int per;
  char grad[5];
};
void main(){
int i,n;
printf("Enter number of students");
scanf("%d",&n);
struct stud s[n];
for(i=1;i<=n;i++)
{
    printf("Enter name of student");
    scanf("%d",s[i].name);
    printf("Enter obtained marks");
    scanf("%d",&s[i].mark);
    s[i].per=s[i].mark/5;
}
for(i=1;i<=n;i++)
{
    if(s[i].per>=80)
     strcpy(s[i].grad,"A");
    else if(s[i].per>=60)
      strcpy(s[i].grad,"B");
    else if(s[i].per>=50)
      strcpy(s[i].grad,"C");
    else if(s[i].per>=40)
     strcpy(s[i].grad,"D");
    else
     strcpy(s[i].grad,"F");
}
for(i=1;i<=n;i++)
{
    printf("&s",s[i].name);
    printf("&d",s[i].mark);
    printf("&d",s[i].per);
    printf("&s",s[i].grad);
}

}

执行此代码时显示错误:

main.c: In function ‘main’:
main.c:25:10: warning: implicit declaration of function ‘strcpy’ [-Wimplicit-function-declaration]
          strcpy(s[i].grad,"A");
          ^~~~~~
main.c:25:10: warning: incompatible implicit declaration of built-in function ‘strcpy’
main.c:25:10: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
main.c:27:11: warning: incompatible implicit declaration of built-in function ‘strcpy’
           strcpy(s[i].grad,"B");
           ^~~~~~
main.c:27:11: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
main.c:29:11: warning: incompatible implicit declaration of built-in function ‘strcpy’
           strcpy(s[i].grad,"C");
           ^~~~~~
main.c:29:11: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
main.c:31:10: warning: incompatible implicit declaration of built-in function ‘strcpy’
          strcpy(s[i].grad,"D");
          ^~~~~~
main.c:31:10: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’
main.c:33:10: warning: incompatible implicit declaration of built-in function ‘strcpy’
          strcpy(s[i].grad,"F");
          ^~~~~~
main.c:33:10: note: include ‘<string.h>’ or provide a declaration of ‘strcpy’

这里有什么错误？

Answer 1

scanf("%d",s[i].name);是未定义的行为。它将是"%s"格式说明符。和printf("%s",s[i].name)不是&s .

包括string.h头文件。

获取输入时数组索引也超出范围。还有未定义的行为。数组索引从 0 开始。所有循环都是 for(i=0;i<=n-1;i++)

并包含这样的标题:

#include <string.h> 

for(i=0;i<=n-1;i++)
{
    printf("Enter name of student");
    scanf("%s",s[i].name);
    printf("Enter obtained marks");
    scanf("%d",&s[i].mark);
    s[i].per=s[i].mark/5;
}

另一个改变

for(i=1;i<=n;i++)
{
    printf("%s",s[i].name);
    printf("%d",s[i].mark);
    printf("%d",s[i].per);
    printf("%s",s[i].grad);
}