c - 在代码块中出现 "implicit declaration of function"错误

Question

我对 C 还是很陌生，我总是在代码块中遇到错误，这使我无法运行我的程序。我收到错误消息“函数 printf_s() 和 scanf_s() 的隐式声明。这是我的代码:

#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>

int main(void)
{
  int age = 0;
  char name[20];

  printf_s("Enter your age: ");
  scanf_s("%d", &age);

  print_s("Enter your name: ");
  scanf_s("%s", name, sizeof(name));

  printf_s("Your name is %s and you are %d years old.\n", name, age);

  return 0;
}

Answer 1

printf_s 和 scanf_s 仅在 __STDC_LIB_EXT1__ 由库实现定义时可用。它是从 C11 标准开始添加的。

首先你必须检查 __STDC_LIB_EXT1__ 是否被定义，然后你才应该使用 printf_s 或 scanf_s。

#define __STDC_WANT_LIB_EXT1__ 1
#include <stdio.h>
int main(void)
{
  int age = 0;
  char name[20];
  #ifdef __STDC_LIB_EXT1__
      printf_s("Enter your age: ");
      scanf_s("%d", &age);
      print_s("Enter your name: ");
      scanf_s("%s", name, sizeof(name));
      printf_s("Your name is %s and you are %d years old.\n", name, age);
  #else
      printf("Enter your age: ");
      scanf("%d", &age);
      print("Enter your name: ");
      scanf("%19s", name);
      printf("Your name is %s and you are %d years old.\n", name, age);
  #endif
  return 0;
}