help with pointers and ints

[agentsmith]

I am writing code that searches a string for a specified character and returns its position in the array. Here's my code so far:

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

int check_for_label (char str[])
{
    char * pch;
    int i;
    for (pch = strchr (str, ':'); pch != NULL; pch = strchr (pch + 1,':'))
    {
        i = pch - str + 1;
    }
    return i;
}
int main ()
{
    int h;
    char label[5];
    char str[] = "for :add $2, $3, $4";
    h = check_for_label (str);
    printf ("%d\n", h);
    return 0;
}

When I run it with the colon in the array, h = 5, and when there's is no colon, h = 0. But when I try to integrate the function into another program, instead of returning h = 0, it returns some random numbers, like 11824 etc instead of 0, but still returns correct h value if there's a colon. I understand that function strchr returns NULL if no matching character is found, so could this be the problem?

[tabstop]

Right -- if there's no colon, then the for loop never happens, which means i never gets set. So you're returning whatever happens to be in i to start with. If you want 0 to be the answer, you should initialize i in check_for_label.

[matsp]

int check_for_label (char str[])
{
    char * pch;
    int i;
    for (pch = strchr (str, ':'); pch != NULL; pch = strchr (pch + 1,':'))
    {
        i = pch - str + 1;
    }
    return i;
}

i is actually not set to anything if pch == NULL in the first search. So you will return some "garbage" - such as 11834 or whatever happens to be in "i" when you return it without entering the for-loop at all (pch == NULL after first strchr()).

--
Mats

[agentsmith]

Great. I set i = 0 in check_for_label() and it all works. Thanks guys