c-带有结构数组的Malloc

Question

我试图创建一个类型为struct的动态分配数组，但遇到了一些问题。即程序在程序末尾的fclose命令处崩溃。在注释完这一行之后，程序在返回0时崩溃，所以我认为我的文件I/O编码有一些问题，内存分配也有问题。我的目标是用文本文件中的值填充结构宿主中包含的值。以下代码：

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<math.h>
#include <assert.h>
#include <stdlib.h>
typedef struct host_struct {
    int x, y, z, w;
    char os[8];
} host;

int main(void)
{
    host *ipArray = NULL;
    int numOfIps = 0;
    char tempFileCharVal = 'a';
    char fileString[8];
    int test;
    int i;
    int j;
    int k;
FILE *hostFile;
    hostFile = fopen("hosts.txt", "r");
    while (fscanf(hostFile, "%c", &tempFileCharVal) != EOF)      //Nested loops to find number of ips, relies on there being a new line at the end of each IP address.
    {
        if (tempFileCharVal == 'n')
        {
            numOfIps++;
        }
    }
    ipArray = malloc(numOfIps * sizeof(*ipArray));                    //Allocates memory to array of ip addresses based on number of IP addresses and size of type host.

    fclose(hostFile);                                   //Reset hostFile to beginning of file.
    hostFile = fopen("hosts.txt", "r");

    for (i = 0; i < (numOfIps); i++)                  //Iterate through IPs, values within IPs, and values within hostFile to assign values to ipArray.
    {
        for (j = 0; j < 5; j++)
        {
            for (k = 0; fscanf(hostFile, "%c", &tempFileCharVal) != '.'; k++)  //?? doesn't end loop if tempFileCharVal = '.'
            {
                if ((tempFileCharVal == ' ' || tempFileCharVal == 'n' || tempFileCharVal == '.') & j != 0) //?? Had to add this if statement to compensate for strange loop behavior.
                {
                    break;
                }
                if ((j == 0) & tempFileCharVal == 'n')
                {
                    fscanf(hostFile, "%c", &tempFileCharVal);
                }
                if ((j == 0) & (tempFileCharVal == '.' || tempFileCharVal == EOF))
                {
                    break;
                }
                fileString[k] = tempFileCharVal;
            }
            fileString[k] = '';
            switch (j)
            {
            case 0:
                ipArray[i].x = atoi(fileString);
                break;
            case 1:
                ipArray[i].y = atoi(fileString);
                break;
            case 2:
                ipArray[i].z = atoi(fileString);
                break;
            case 3:
                ipArray[i].w = atoi(fileString);
                break;
            case 4:
                strcpy(ipArray[i].os, fileString);
                ipArray[i].os[k] = '';
                break;
            }
        }
    }
    //fclose(hostFile);
    free(ipArray);
    return(0);
}

Answer 1

您必须小心这一行：

ipArray = malloc(numOfIps * sizeof(*ipArray)); 

"ipArray"的类型为指针！不过你需要更多的内存。正确的做法是写：

ipArray = malloc(numOfIps * sizeof(struct host_struct)); 

编辑：我现在看到这个已经被评论了，好像我迟到了，对不起！；-）

编辑：我错了，希望我没有迷惑任何人！