c - 无法正确访问结构体内容

Question

我没有得到以下字符串输出:

struct stringItem {
    int len;
    char str[1];
}


void allocationStringBuffer (char* stringContent, struct stringItem *string) {

    // dynamically sized object
    int n;
    n = strlen(stringContent);

    //struct stringItem *string = malloc(sizeof(struct stringItem) + n);
    string = malloc(sizeof(struct stringItem) + n);

    if (string == NULL) {             // check if malloc is successful
       printf("Memory allocation for string fails.\n");
       // exit(-1);
    }   

   strcpy(string->str, stringContent);
   printf("Struct string: %s\n", string->str);
   string->len = n;     
}


在主要部分:

 
struct stringItem *string2;

allocationStringBuffer ("helloWorld", string2);

printf("Struct string: %s\n", (*string2).str);
free(string2);

allocationStringBuffer ("another Statement...", string2);
printf("Struct string: %s\n", string2->str);
free(string2);


结果是:

 
Struct string: helloWorld
Struct string:  ÉÉÉÉÉï Uï∞â∞¶SVWh♦☺
Struct string: another Statement...
Struct string:  ÉÉÉÉÉï Uï∞â∞¶SVWh♦☺


感谢您的帮助。

 
[Updates with Thanks to ALL]
Here is the full working code. It has been resolved. Thank you to ALL.

struct stringItem {
    int len;
    char str[1];
};


void allocationStringBuffer (char* stringContent, struct stringItem** pstring) {

    // dynamically sized object
    int n;
    n = strlen(stringContent);

    struct stringItem *string;
    string = malloc(sizeof(struct stringItem) + (n+1));

    if (string == NULL) {             // check if malloc is successful
       printf("Memory allocation for string fails.\n");
       // exit(-1);
    }   

   strcpy(string->str, stringContent);
   printf("Struct string: %s\n", string->str);
   string->len = n;     

   *pstring = string;  // Copy allocated pointer to out-parameter.
}




在主目录

    

结构体 stringItem *string2;

AllocationStringBuffer("helloWorld", &string2);

printf("结构字符串: %s\n", (*string2).str);
自由(字符串2)；

allocateStringBuffer("另一条语句...", &string2);
printf("结构字符串: %s\n", string2->str);
自由(字符串2)；

			            

Answer 1

在我看来，您需要进行这些更改:

allocationStringBuffer ("helloWorld", &string2);  // Pass ADDRESS of string2, not just string2

<小时/>

void allocationStringBuffer (char* stringContent, struct stringItem **pstring)
{
    // dynamically sized object
    int n;
    n = strlen(stringContent);

    struct stringItem* string;  // Local variable, will be later copied to function parameter.
    string = malloc(sizeof(struct stringItem) + n);

    if (string == NULL) {             // check if malloc is successful
       printf("Memory allocation for string fails.\n");
       // exit(-1);
    }   

   strcpy(string->str, stringContent);
   printf("Struct string: %s\n", string->str);
   string->len = n;     

   *pstring = string;  // Copy allocated pointer to out-parameter.
}