gets函数在何种情况下能够使用

关于gets函数：

gets函数是一个很有争议的函数，因为它存活了一段时间，然后有被废弃了。

C99官方文档（第297页）：

7.19.7.7 The gets function
Synopsis
1 #include <stdio.h>
char *gets(char *s);
Description
2 The gets function reads characters from the input stream pointed to by stdin, into the
array pointed to by s, until end-of-file is encountered or a new-line character is read.
Any new-line character is discarded, and a null character is written immediately after the
last character read into the array.
Returns
3 The gets function returns s if successful. If end-of-file is encountered and no
characters have been read into the array, the contents of the array remain unchanged and a
null pointer is returned. If a read error occurs during the operation, the array contents are
indeterminate and a null pointer is returned.

C11官方文档（前言，第14页）：

removed the gets function (<stdio.h>)

C99文档告诉我们，gets函数的返回值是字符串的首地址，然后C11文档告诉我们，gets函数已经被移除了，实际上，在C11中并没有移除gets函数，直到C14才完全移除了gets函数，笔者做了如下实验。

示例程序：

#include <bits/stdc++.h>
using namespace sts;
int main(void){
    char a[10];
    gets(a);
    return 0;
}

然后分别用C98，C11，C14，C17运行了一下，结果如下：

g++ -o test test.cpp -std=c++98抛出waring，gets is dangerous
g++ -o test test.cpp -std=c++11抛出waring，gets is dangerous
g++ -o test test.cpp -std=c++14抛出error，gets is not declared
g++ -o test test.cpp -std=c++17抛出error，gets is not declared

所以，如果我们用了C14以上版本，我们就不要使用gets函数了。