Thread: Array of pointers with addresses of words

Task: Write a function that takes as parameter a string, an array of pointers and its length and fills the array with addresses to the beginning of each (whitespace-separated) word in the string (similar to the argv[] array of main). Terminate the array with a NULL pointer after the last valid address.
I have some questions. 'An array of pointers' = array of addresses (correct me if I'm wrong I'm learning pointers). From what I know an address is a huge number, so how can I store the addresses of the words in the array, without overflowing it?

Code:

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
void wordAdresses(char *s, int *ptr_arr, int cap)
{
    ptr_arr[0] = '\0';
    cap = 1;
    char* word = strtok(s, " ");
    while(word != NULL)
    {
        int address = *word;
        ptr_arr[cap] = *word;
        cap++;
        if(address+1 > cap)
        {
            printf("String overflow\n");
        }
        cap -= address;
        //printf("Word is %s <--> Value is %X\n",word, word);
        word = strtok(NULL, " ");
    }
    for(int i = 0; i < cap; i++)
    {
        printf("%d\n", ptr_arr[i]);
    }
}
int main()
{
    char s[] = "john goes to school";
    int ptr_arr[100];
    wordAdresses(s, ptr_arr, sizeof ptr_arr);
    return 0;
}

Output:
String overflow
String overflow
String overflow
String overflow

Now if I put the last for between comments and remove them for the second printf

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
void wordAdresses(char *s, int *ptr_arr, int cap)
{
    ptr_arr[0] = '\0'; 
    cap = 1;
    char* word = strtok(s, " ");
    while(word != NULL)
    {
        int address = *word;
        ptr_arr[cap] = *word;
        cap++;
        if(address+1 > cap)
        {
            printf("String overflow\n");
        }
        cap -= address;
        printf("Word is %s <--> Value is %X\n",word, word);
        word = strtok(NULL, " ");
    }
   /* for(int i = 0; i < cap; i++)
    {
        printf("%d\n", ptr_arr[i]);
    }*/
}
int main()
{
    char s[] = "john goes to school";
    int ptr_arr[100];
    wordAdresses(s, ptr_arr, sizeof ptr_arr);
    return 0;
}

Output:
String overflow
Word is john <--> Value is 61FE00
String overflow
Word is goes <--> Value is 61FE05
String overflow
Word is to <--> Value is 61FE0A
String overflow
Word is school <--> Value is 61FE0D

So I get the adress of the beginning of each word, but also the message "String overflow" because the numbers are huge. So how can I put the addresses into the array and avoid overflowing?

Is this correct?

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
void wordAdresses(char *s, int *ptr_arr, int cap)
{
    ptr_arr[0] = '\0';
    unsigned i, countWords = 0;
    char* word = strtok(s, " ");
    while(word != NULL)
    {
        cap = 1;
        for(i = 0; i < cap; i++)
        {
            *(ptr_arr+i) = word;
            printf("Word %s has address %X\n",word, *(ptr_arr+i));
        }
       // printf("Word is %s <--> Value is %X\n",word, word);
        word = strtok(NULL, " ");
        cap++;
    }
}
int main()
{
    char s[] = "john goes to school";
    int ptr_arr[100];
    wordAdresses(s, ptr_arr, 100);
    return 0;
}

Output:
Word john has address 61FE00
Word goes has address 61FE05
Word to has address 61FE0A
Word school has address 61FE0D

Now I would also need to watch for array overflow. What would be the condition for cap(cap < ? ), which if met, would overflow the array?

Damn, yeah I treated it as an array of characters by mistake and I wanted to make sure that it is empty and null-terminated in the beginning. What would be the alternative to make sure my array isn't overflowing? Should I subtract from cap the size of a word in bytes to check if it overflows?

Thanks a lot, it's so much clearer now! Just to make sure I understood fully, you wrote i < cap - 1 because we don't take the terminator '\0' into a account, right?