字符串的動態內存分配函數，直到換行

Question

早些時候，我只是試圖爲未知長度的字符串（即逐字符讀取，直到遇到換行符）分配內存的函數。

現在，我的問題是關於我的字符串（命名爲s）版本的分配內存。 我試圖用免費（s）做到這一點。問題是我不知道我應該在哪裏寫它..

如果我在函數之前寫入「return s」，那麼顯然它會返回一個未分配的指針。

如果我在「return s」之後的函數中寫入它，我不認爲它會產生影響，對吧？因爲s在main（）中返回，所以它永遠不會被釋放。

我該怎麼做或想到這種情況？

這是我得到：

#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

考慮的性質或您的input_string_line（）函數，你應該釋放你的指針是在主要功能的唯一地方。任何其他地方都會產生無效指針或導致內存泄漏。

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