字符串的动态内存分配函数，直到换行

Question

早些时候，我只是试图为未知长度的字符串（即逐字符读取，直到遇到换行符）分配内存的函数。

现在，我的问题是关于我的字符串（命名为s）版本的分配内存。 我试图用免费（s）做到这一点。问题是我不知道我应该在哪里写它..

如果我在函数之前写入“return s”，那么显然它会返回一个未分配的指针。

如果我在“return s”之后的函数中写入它，我不认为它会产生影响，对吧？因为s在main（）中返回，所以它永远不会被释放。

我该怎么做或想到这种情况？

这是我得到：

#include <stdlib.h> 
#include <stdio.h> 

//Returns dynamic allocated string(read until the '\n' aka. newline character) 
char* input_string_line() 
{ char *s,*aux,c;      //*s(string pointer),*aux(auxiliary string pointer),c(the characters that are read) 
    int len;       //len(actual length of the string) 
    s=malloc(sizeof(char));    //firstly, allocation memory for 1 byte(8 bites), for the null character 
    if (!s)        //verification if the memory can be allocated, if not possible then the program exits 
    { printf("ERROR: Memory allocation failure (string).\n"); 
     exit(EXIT_FAILURE); } 
    s[0] = 0;       //NULL character for string ending 
    len = 0;       //the length of the string at the beginning is 0(without considering the NULL character at the end) 
    while ((c = getchar()) != '\n')  //reading character by character until newline 
    { aux = realloc(s, len + 2);  //reallocation memory for the next read character in a new auxiliary string(same as the old string, this time having memory for a new character to be added) 
     if (!aux)      //verification if the reallocation can succed: if not possible then the program exits 
     { free(s); 
      printf("ERROR: Memory allocation failure (auxiliary string).\n"); 
      exit(EXIT_FAILURE); } 
     else s = aux;     //if succeded, then the string becomes the auxiliary string 
     s[len] = c;      //the character with the [len] index will be assigned the value of the read character 
     s[len+1] = 0;     //NULL character for string ending 
     len++; }      //length increments by one each time a new character is added to the string 
    return s; 
    free(s);       
} 

int main() 
{ printf("%s",input_string_line()); 
return 0;} 

Answer 1

考虑的性质或您的input_string_line（）函数，你应该释放你的指针是在主要功能的唯一地方。任何其他地方都会产生无效指针或导致内存泄漏。

int main() 
{ 
    char* s = input_string_line(); 
    printf("%s",s); 
    free(s); 
    return 0; 
}