出现分段错误:iogetline。c

以下代码是问题部分:

#define NICKLEN 10
...

typedef char * string;
typedef struct donation
{
    string nickname;
    ...
} Item;

...

void eatline(void)
{
  while (getchar()!='\n');
}

...

string s_gets(string st, int n)
{
  string ret_val;
  string find;

  ret_val=fgets(st, n, stdin);
  if (ret_val)
  {
    find=strchr(st, '\n');
    if (find)
      *find='\0';
    else
      eatline();
  }

  return ret_val;
}

...

int main(void)
{
  Item donate;

...

puts("Enter y to start");

while(getchar()=='y')
{
  eatline(); // to remove \n from input
  puts("Enter nickname. Limit is 10 characters.");
  s_gets(donate.nickname, NICKLEN);
...

以下是输入、输出

Enter y to start

y
Enter nickname. Limit is 10 characters.

ffff

输入昵称时,发生错误(在gdb中):

iogetline.c: No such file or directory.