C链表:访问冲突读取位置0x00000001

Question

我是一个很新的链表，需要一点帮助。目前我收到这个错误"

0x0FD940C1 (msvcr120 .dll)中的未处理异常ConsoleApplication1.exe: 0xC0000005:访问违规读取位置0 x00000001。

程序试图做的是取一个文件，遍历它并创建一个链表，每个节点由字符串值和指向下一个节点的节点指针组成。我已经遵循了多个教程，我不确定问题是什么。如果有人能帮忙，那就太好了。

下面是我的代码:

#ifdef _WIN32
#define _CRT_SECURE_NO_DEPRECATE
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define BUFF_SIZE 300
typedef struct node {
    char stringDat[BUFF_SIZE];
    struct node* next;
} NODE;
int main(int argc, char** argv) {
    FILE* fp;
    FILE* fpLogFile;
    char* fileLoc = "C:\Users\David\Desktop\data.dat";
    char* logFile = "C:\Users\David\Desktop\log.txt";
    char buff[BUFF_SIZE]; 
    int i, nodeCnt;
    if ((fp = fopen(fileLoc, "rb+")) == NULL) {
        printf("FILE OPEN ERROR ON EXISTING FILEn");
        exit(1);
    }
    if ((fpLogFile = fopen(logFile, "w")) == NULL) {
        printf("Error opening log filen");
        exit(1);
    }
    // root node
    NODE* root = NULL;
    // provide memory for root node
    root = malloc(sizeof(NODE));
    if (root == NULL){
        return 1;
    }
    fprintf(fpLogFile, "%sn", "ROOT MALLOC");
    nodeCnt = 1;
    // assign values to root node
    root->next = NULL;
    fprintf(fpLogFile, "%sn", "ROOT Next = 0");
    strcpy(root->stringDat, fread(buff, 20, 1, fp));
    fprintf(fpLogFile, "%sn", "ROOT buff");
    // set curr to root node
    NODE* curr = root;
    fprintf(fpLogFile, "%sn", "Curr = ROOT");
    while (fread(buff, 20, 1, fp) != NULL) {
        // navigate to last node in list
        while (curr->next != NULL) {
            curr = curr->next;
        }
        fprintf(fpLogFile, "%sn", "Curr = last node");
        // Create node at end of list
        curr->next = malloc(sizeof(NODE));
        fprintf(fpLogFile, "%sn", "Malloc new Node");
        nodeCnt++;
        // move current node to last node
        curr = curr->next;
        if (curr == 0) {
            fprintf(fpLogFile, "%sn", "Out of memory");
            return 0;
        }
        // assign val to current stringDat
        strcpy(curr->stringDat, buff);
        fprintf(fpLogFile, "%s     %d    %p    %dn", curr->stringDat, strlen(curr->stringDat), curr->next, nodeCnt);
        for (i = 0; i < BUFF_SIZE; i++) {
            buff[i] = 0;
        }

    }
    while ((curr = root) != NULL) { // set curr to head, stop if list empty.
        root = root->next;          // advance head to next element.
        free(curr);                // delete saved pointer.
    }
    fclose(fp);
    fclose(fpLogFile);
    return 0;
}

Answer 1

This:

strcpy(root->stringDat, fread(buff, 20, 1, fp));

没有意义，应该触发编译器警告。

strcpy()的第二个参数是一个字符串指针，但fread()返回size_t(它成功读取的"元素"的数量)。当它在这里成功时，它将返回1，这将触发您得到的错误。

你的意思:

if(fread(buff, 20, 1, fp) == 1)
  strcpy(root->stringDat, buff);