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user366097
Asked:2021-01-01 01:57:19 +0000 UTC2021-01-01 01:57:19 +0000 UTC

C中指针的怪异

  • 772

我想知道为什么这个程序在没有分段错误的情况下工作：

#include <stdio.h>

char *month_name(int);

main()
{
    char *month[15];
    for(int i = 1, j = 0; month_name(i) != "No month"; i++, j++)
    {
        month[j] = month_name(i);
        while(*month[j])
        {
            printf("%c", *month[j]++);

            if(!*month[j])
            {
                printf("\n");
            }
        }
    }
}

char *month_name(int num)
{
    static char *name[] = {
        "No month", "January", "February", 
        "Mart", "April", "May", "June", 
        "July", "August", "September", "October", 
        "November", "December"
    };
    return (num < 1 || num > 12) ? name[0] : name[num];
}

而这个有分段错误并在屏幕上显示奇怪的字符：

#include <stdio.h>

char *month_name(int);

main()
{
    char *month[15];
    int k = 0;
    for(int i = 1, j = 0; month_name(i) != "No month"; i++, j++)
    {
        month[j] = month_name(i);
    }

        !!!!!
        while(*month[k])
        {
            printf("%c", *month[k]++);

            if(!*month[k])
            {
                printf("\n");
                k++;
            }
        }
        !!!!!

}

char *month_name(int num)
{
    static char *name[] = {
        "No month", "January", "February", 
        "Mart", "April", "May", "June", 
        "July", "August", "September", "October", 
        "November", "December"
    };
    return (num < 1 || num > 12) ? name[0] : name[num];
}
c

1 个回答

  1. Best Answer

    像这样

    month_name(i) != "No month"

    一般不能写。如果它正确地为您工作，那么仅仅是因为优化，它结合了相同的只读行。一旦您将带有密钥的代码编译到 VC++/GF-中，一切都会立即停止工作......

    在第二种情况下，您只需遍历指针数组（因为k++）并在 12 月跳出到下一个指针 - 它包含某种指向其他垃圾的垃圾，这些垃圾正试图退出或崩溃。

    所以如果你写

    char *month[15] = {"","","","","","","","","","","","","","",""};

    那么一切都会奏效:)

    • 3

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