Will this leak memory?

Question

Hello. I made a small function to catenate strings and return the combined string. However since I assign memory to a third variable in the function, will the memory be freed when the function finishes or will it stay there, requiring me to free it later? and if I need to free it, what's the most stylish solution to do it?

Here's the test code. It works, but I can't tell if that memory is freed or not with my tools.

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

char * StrCat(const char *st1, const char *st2){
    char *string = calloc((strlen(st1) + strlen(st2) + 1), sizeof(char));
    strcat(string, st1);
    strcat(string, st2);
    return string;
}

int main(){
    printf("String: %s\n", StrCat("HELLO ", "WORLD"));
    return 0;
}

Answer 1

Yes you need to free it.

Probably something like:

int main(){
    char *s = StrCat("HELLO ", "WORLD");
    printf("String: %s\n", s);
    free(s);
    return 0;
}

Answer 2

Yes, you have to free it. Try valgrind to detect the leak.

Answer 3

Yes. If you call calloc, malloc, new, etc. a call to a function that frees the memory must also be made.

Answer 4

Since the applications ends right after printf, there's really no need to free it, since the application will do that for you when it dies. But yes, it's always good practice to free it.