you keep incrementing the str pointer. When you return it, it is pointing to the nul-terminator, so it's effectively an empty string. Also, you overflow the char datatype by adding 13 to the last ASCII letters (e.g. 'z' + 13)

sizeof(int *) is wrong, should be sizeof(int).

asprintf is not standard

712,577,413,488,402,631,964,821,329 is bigger that the space for read using %ld Long int -> 2,147,483,647 https://en.wikipedia.org/wiki/C_data_types
you need work with parts of numbers using a string for keep the total

It's written in the description :

In C, the initial dimensions of the GoL universe is passed into your function by reference via the pointers rowptr and colptr.

The kata is great imo, but is seems pretty similar to this one (please correct me if i'm wrong!).

Hey, guys, I'm having trouble with this one... Here's my code:

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>

char *strsum(const char *a, const char *b){
char *str;

asprintf(&str, "%ld", atol(a)+atol(b));

return str;

}

But i keep receiving the following error:

*Actual: -2
Expected: 712577413488402631964821329
Arg A: 712569312664357328695151392
Arg B: 8100824045303269669937

I'm almost sure this is a overflow error... However I don't know how to solve it... Can someone help me out?

Wooow, thank you, man! Silly mistake.. XD

Read this. Check how you calculate r, is n an int?