如何修复C语言中的分段故障错误？

Question

我是C语言新手，我想不通。代码编译后让我运行一次，但当我输入时，却给我分段故障。我运行gdb，回溯发现分段故障是在 int main () 在 commissionOfAMechanic(name，&%)。 但我不知道如何让它工作。如果有人能给我任何类型的建议来解决这个错误。我在代码中使用的文件在底部。

#include <stdio.h> 
#include <string.h>
#include <assert.h>
#include <stdlib.h>

void commissionOfAMechanic (char *mechanicName, int *comm)
{
    FILE * fp = fopen ("NameCommissions.txt", "r");
    if ( fp == NULL )
    {
        printf ( "Unable to open the file\n" );
        exit (-1);
    }

    char temp [16];
    int commission;

    int i;
    for ( i = 0 ; i < 4 ; i++ )
    {
        fscanf ( fp, "%s %d", temp, *comm);
        if (temp, *mechanicName)
            break;
    }

    fclose (fp);
    printf ( "The name given is %s and his commission is %d \n", temp, *comm );
}

void priceOfAllServices ( float pr[])
{
    FILE * fp = fopen ( "PriceOfServices.txt", "r");
    if (!fp)
    {
        printf ( "Can't open file.\n");
        exit (-1);
    }

    char temp [16];
    fscanf (fp, "%s %d", temp, &pr[0]);
    fscanf (fp, "%s %d", temp, &pr[1]);
    fscanf (fp, "%s %d", temp, &pr[2]);
    fscanf (fp, "%s %d", temp, &pr[3]);

    fclose (fp);
}

void getWeeklyStatsOfaMechanic (char *name, int jobs[])
{
    FILE * fp = fopen ("JobsDone.txt", "r");
    if (! fp)
    {
        printf ("Can't open file.\n");
        exit (-1);
    }

    char temp [16];
    fscanf (fp, "%s %d", temp, &jobs[0]);
    fscanf (fp, "%s %d", temp, &jobs[1]);
    fscanf (fp, "%s %d", temp, &jobs[2]);
    fscanf (fp, "%s %d", temp, &jobs[3]);



    int i;
    for ( i = 0 ; i < 4 ; i++ )
    {
        fscanf (fp, "%s%d%d%d%d", temp, jobs[0], jobs[1], jobs[2], jobs[3]);
        if (strcmp (temp, name ))
        {
            break;
        }
    }
    printf ( "Jobs done by %s %d %d %d %d \n", temp, jobs[0], jobs[1], jobs[2], jobs[3]);
    fclose (fp);
}

int main ()
{
    int percent;
    char name[16];
    int jobs[4];
    float prices[4];

    printf ( "Please enter the name of the Mechanic\n");
    scanf ("%s", name);

    commissionOfAMechanic (name, &percent);

    priceOfAllServices (prices);

    getWeeklyStatsOfaMechanic (name, jobs);

    float total = jobs[0]*prices[0] +
                  jobs[1]*prices[1] +
                  jobs[2]*prices[2] +
                  jobs[3]*prices[3];

    printf ( "Name = %s Total Commission = %.2f\n", name, total);

    return 0;
}

Answer 1

在你的代码中，你要求fscanf从你的文件中读取，然后把结果写到地址*comm，其中comm是一个整数，fscanf把它的值作为一个指针（当然这指向的是无效的内存）。另外在你的临时缓冲区中，当你读取一个大于16字节的字符串时，你可能会出现缓冲区溢出。使用fgets代替fscanf来控制你的输入。

解决方法：在你的临时缓冲区中，当你读取大于16字节的字符串时，可能会出现缓冲区溢出。

void commissionOfAMechanic (char *mechanicName, int *comm)
{
     FILE * fp = fopen ("NameCommissions.txt", "r");

     if ( fp == NULL )
     {
         printf ( "Unable to open the file\n" );
         exit (-1);
     }

     char temp [16];
     int commission;

     int i;
     for ( i = 0 ; i < 4 ; i++ )
     {
         fscanf ( fp, "%s %d", &temp, comm);

         if (temp, *mechanicName) // i am not sure what you are doing here, maybe you mean if(strcmp(temp, mechanicName) == 0) ?
             break;
     }

     fclose (fp);
     printf ( "The name given is %s and his commission is %d \n", temp, *comm );
}

同样在你的... void getWeeklyStatsOfaMechanic (char *name, int jobs[])您在使用fscanf时也有同样的问题。

void getWeeklyStatsOfaMechanic (char *name, int jobs[])
{
       FILE * fp = fopen ("JobsDone.txt", "r");

       if (! fp)
       {
          printf ("Can't open file.\n");
          exit (-1);
       }

       char temp [16];
       fscanf (fp, "%s %d", &temp, &jobs[0]);
       fscanf (fp, "%s %d", &temp, &jobs[1]);
       fscanf (fp, "%s %d", &temp, &jobs[2]);
       fscanf (fp, "%s %d", &temp, &jobs[3]);


       int i;

       for ( i = 0 ; i < 4 ; i++ )
       {
           fscanf (fp, "%s%d%d%d%d", &temp, &jobs[0], &jobs[1], &jobs[2], &jobs[3]);

           if (strcmp (temp, name ))
           {
                break;
           }
       }
       printf ( "Jobs done by %s %d %d %d %d \n", temp, jobs[0], jobs[1], jobs[2], jobs[3]);
       fclose (fp);
    }

同时在你的主 。

scanf("%s", &name);