Thread: strange behaviour

Hi all.

The value of the first 2 character members of the structure are the same, so why does the first if condition keep executing? Why doesn't the second if execute?

Thank you.

Code:

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

int main(void)
{
    struct Char
    {
        char ch;
        int ctr;
    };

    char *ptr[5], temp;
    int count, compval;
    struct Char list[5] = { {'x', 23}, {'x', 4}, {'i', 83}, {'s', 34}, {'a', 12} };

    printf("Before sort: ");

    for(count = 0; count < 5; count++)  // initialise pointers
    {
        ptr[count] = &list[count].ch;
        printf("%c ", *ptr[count]);
    }

    for(count = 0; count < 4; count++)
    {
        if((compval = strcmp(ptr[count], ptr[count + 1])) > 0)      // ptr[count] > ptr[count + 1]
        {
            temp = list[count].ch;
            list[count].ch = list[count + 1].ch;
            list[count + 1].ch = temp;
        }

        if((compval = strcmp(ptr[count], ptr[count + 1])) == 0)     // ptr[count] == ptr[count + 1]
        {
            puts("values are equal");
            break;
        }
    }

    printf("\nAfter sort:  ");

    for(count = 0; count < 5; count++)
        printf("%c ", *ptr[count]);

    return 0;
}

You're using strcmp() on things which do NOT have a \0 at the end of them.

Try

Code:

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

int main(void)
{
    struct Char
    {
        char *ch;
        int ctr;
    };

    char *ptr[5], *temp;
    int count, compval;
    struct Char list[5] = { {"x", 23}, {"x", 4}, {"i", 83}, {"s", 34}, {"a", 12} };

    printf("Before sort: ");

    for(count = 0; count < 5; count++)  // initialise pointers
    {
        ptr[count] = list[count].ch;
        printf("%c ", *ptr[count]);
    }

    for(count = 0; count < 4; count++)
    {
        if((compval = strcmp(ptr[count], ptr[count + 1])) > 0)      // ptr[count] > ptr[count + 1]
        {
            temp = list[count].ch;
            list[count].ch = list[count + 1].ch;
            list[count + 1].ch = temp;
        }

        if((compval = strcmp(ptr[count], ptr[count + 1])) == 0)     // ptr[count] == ptr[count + 1]
        {
            puts("values are equal");
            break;
        }
    }

    printf("\nAfter sort:  ");

    for(count = 0; count < 5; count++)
        printf("%c ", *ptr[count]);

    return 0;
}

It doesn't sort, but it doesn't crash either.

Perhaps single step the code in a debugger and see what your break statement is for.

Thanks Salem!