c++ - 读取位置 0x00000000 时发生访问冲突

Question

学习一段时间c后 用vs2015编写的小程序，代码如下：

//14-9.c
#include "stdafx.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "14-9.h"

int main()
{
    int flight;
    char choice;
    struct plane seat[FLIGHTNUM][SEATS];
    FILE *data;
    Process mode[5] = { show_empty_number,show_empty_list,show_alphabetical_list,add_assign,del_assign };
    if (fopen_s(&data, "SeatsData.dat", "r") == 0)
    {
        for (int f = 0; f < FLIGHTNUM; f++)
            load_file(data, seat[f]);
        fclose(data);
    }
    for (int f = 0; f < FLIGHTNUM; f++)
        for (int n = 0; n < SEATS; n++)
        {
            seat[f][n].number = n + 1;
            if (!seat[f][n].sold)
            {
                clean_name(&seat[f][n]);
            }
        }
    flight = choose_flight();
    if (flight != 4)
        do {
            do {
                choice = menu();
                if (!strchr("abcdefq", choice))
                {
                    printf("Input error. Please try again.\n");
                    continue;
                }
            } while (!strchr("abcdefq", choice));
            if(strchr("abcd",choice))
                (mode[choice - 'a'])(seat[flight]);
            switch (choice)
            {
                case 'f':
                check_status(flight, seat[flight]);
                break;
                case 'q':
                printf("\n");
                flight = choose_flight();
                break;
            }
            numsort(seat[flight]);
        } while (flight != 4);
    fopen_s(&data, "SeatsData.dat", "w");
    for (int f = 0; f < FLIGHTNUM; f++)
    {
        fprintf(data, "=======%s======\n", flight_list[f]);
        for (int n = 0; n < SEATS; n++)
        {
            fprintf(data, "%2d %s %s %s\n", n + 1, (seat[f][n].sold) ? "Sold " : "Empty", seat[f][n].fname, seat[f][n].lname);
            free(seat[f][n].fname);
            free(seat[f][n].lname);
        }
    }
    fclose(data);
    getchar();
    return 0;
}

以下是包含的头文件14-9.h:

//14-9.h
#define SEATS 12
#define FLIGHTNUM 4
#define NMAX 15
#define DATAMAX 40
#define SOLDPOS 3
#define NAMEPOS 9
struct plane
{
    int number;
    bool sold = 0;
    char *lname;
    char *fname;
};

typedef void(*Process)(struct plane *);
char *flight_list[4] = { "Flight 102","Flight 311","Flight 444","Flight 519" };

void clean_name(struct plane *seat)
{
    seat->fname = (char *)malloc(1);
    seat->lname = (char *)malloc(1);
    seat->fname[0] = '\0';
    seat->lname[0] = '\0';
}

void load_file(FILE *data, struct plane *seat)
{
    static int load_time = 0;
    char dataline[DATAMAX];
    fgets(dataline, DATAMAX, data);
    for (int n = 0; n<SEATS && fgets(dataline, DATAMAX, data) ; n++)
        if (dataline[SOLDPOS] == 'S')
        {
            int pos = NAMEPOS;
            int length;
            seat[n].sold = 1;
            char temp[NMAX];
            memset(temp, '\0', NMAX);
            for (int m = 0; isalpha(dataline[pos]); m++, pos++)
                temp[m] = dataline[pos];
            pos++;
            length = strlen(temp) + 1;
            seat[n].fname = (char *)malloc(length);
            strcpy_s(seat[n].fname, length, temp);
            memset(temp, '\0', NMAX);
            for (int m = 0; isalpha(dataline[pos]); m++, pos++)
                temp[m] = dataline[pos];
            length = strlen(temp) + 1;
            seat[n].lname = (char *)malloc(length);
            strcpy_s(seat[n].lname, length, temp);
        }
}

int choose_flight(void)
{
    int flight;
    do {
        printf("Please enter the label of the flight you want to process.\n");
        for (int n = 0; n < FLIGHTNUM; n++)
            printf("%d)%s\n", n + 1, flight_list[n]);
        printf("5)quit      ");
        scanf_s("%d", &flight);
        getchar();
        printf("\n");
        if (flight>5 && flight<0)
        {
            printf("Input error. Please try again.\n");
            continue;
        }
    } while (flight > 5 && flight < 1);
    if (flight == 5)
        printf("Bye!");
    return (flight-1);
}

void deln(char *str)
{
    int n = 0;
    while (1)
    {
        if (str[n] == '\n')
        {
            str[n] = '\0';
            break;
        }
        n++;
    }
}
void getname(struct plane * one)
{
    char temp[NMAX];
    int length;
    printf("Please enter the passenger's first name:");
    fgets(temp, NMAX, stdin);
    deln(temp);
    length = strlen(temp) + 1;
    one->fname = (char *)malloc(length);
    strcpy_s(one->fname, length, temp);
    printf("Please enter the passenger's last name:");
    fgets(temp, NMAX, stdin);
    deln(temp);
    length = strlen(temp) + 1;
    one->lname = (char *)malloc(length);
    strcpy_s(one->lname, length, temp);
}

char menu(void)
{
    char choice;
    printf("To choose a function, enter its letter label:\n");
    printf("a) Show number of empty seats\n");
    printf("b) Show list of empty seats\n");
    printf("c) Show alphabetical list of seats\n");
    printf("d) Assign a customer to a seat assignment\n");
    printf("e) Delete a seat assignment\n");
    printf("f) Check status of a seat\n");
    printf("q) Quit to the menu of choosing the flight.      ");
    scanf_s("%c", &choice, 1);
    getchar();
    return choice;
}

void show_empty_number(struct plane *seat)
{
    int empty = 0;
    for (int n = 0; n < SEATS; n++)
    {
        if (seat[n].sold)
            continue;
        empty++;
    }
    printf("\nThere are %d empty seats.\n\n", empty);
}

void show_empty_list(struct plane *seat)
{
    printf("\nEmpty seats:");
    for (int n = 0; n < SEATS; n++)
        if (!seat[n].sold)
            printf("#%d ", seat[n].number);
    printf("\n\n");
}

void show_alphabetical_list(struct plane *seat)
{
    struct plane temp;
    int top, seek;
    for (top = 0; top < SEATS - 1; top++)
    {
        for (seek = top + 1; seek < SEATS; seek++)
        {
            if (seat[top].sold && seat[seek].sold)
            {
                if (strcmp(seat[top].fname, seat[seek].fname) > 0)
                {
                    temp = seat[top];
                    seat[top] = seat[seek];
                    seat[seek] = temp;
                }
                if (strcmp(seat[top].lname, seat[seek].lname) == 0 && strcmp(seat[top].lname, seat[seek].lname) > 0)
                {
                    temp = seat[top];
                    seat[top] = seat[seek];
                    seat[seek] = temp;
                }
            }
        }
    }
    for (int n = 0; n < SEATS; n++)
    {
        if (seat[n].sold)
            printf("\n%s %s   #%d\n", seat[n].fname, seat[n].lname, seat[n].number);
        continue;
    }
    printf("\n");
}

void add_assign(struct plane *seat)
{
    int n;
    printf("\nPlease enter the number of the seat:");
    scanf_s("%d", &n);
    getchar();
    if (seat[n - 1].sold)
    {
        printf("The seat has been sold.\n\n");
        return;
    }
    getname(&seat[n - 1]);
    seat[n - 1].sold = 1;
    printf("The info has been added.\n\n");
}

void del_assign(struct plane *seat)
{
    int n;
    printf("\nPlease enter the number you want to delete.");
    scanf_s("%d", &n);
    getchar();
    if (!seat[n - 1].sold)
    {
        printf("It hasn't been sold.\n\n");
        return;
    }
    seat[n - 1].sold = 0;
    clean_name(&seat[n]);
    printf("The assignment has been deleted.\n\n");
}

void check_status(int f,struct plane *seat)
{
    int n;
    printf("\nEnter the seat number you want to check.");
    scanf_s("%d", &n);
    getchar();
    printf("%s :#%d %s %s %s\n\n", flight_list[f], n, (seat[n-1].sold) ? "Sold " : "Empty", seat[n-1].fname, seat[n-1].lname);
}

void numsort(struct plane *seat)
{
    struct plane temp;
    int top, seek;
    for (top = 0; top < SEATS - 1; top++)
    {
        for (seek = top + 1; seek < SEATS; seek++)
        {
            if (seat[top].number > seat[seek].number)
            {
                temp = seat[top];
                seat[top] = seat[seek];
                seat[seek] = temp;
            }
        }
    }
}

问题已解决。

Answer 1

Add an if(flight != 4)

before calling the numsort function

Answer 2

What about the error message and execution process