Thread: Proper way to free a pointer returned from a function

I am going through the Understanding and Using C Pointers book and came across one example function for combining variables into a single buffer using snprintf.

There is no example main for the problem within the book (it just says to pass a buffer and its size and that a pointer is returned). So I tried to make my own main()/client for the function and I am unsure of the best way to do it.

Here is the function:

Code:

char* format(char *buffer, size_t size, const char* name, size_t quantity, size_t weight) {
    snprintf(buffer, size, "Item: %s  Quantity: %zu  Weight: %zu", name, quantity, weight);
    return buffer;
}

And here are the two ways that I tried calling it:

Method 1:

Code:

int main () {
    char *buffer = malloc(sizeof(char) * 1024);
    printf("%s\n",format(buffer,1024,"Axle",25,45));
    free(buffer);
    return 0;
}

Method 2:

Code:

int main () {
    char buffer[128];
    printf("%s\n",format(buffer,sizeof(buffer),"Axle",25,45));
    return 0;
}

I think it's pretty clear that Method 1 requires free() because of the use of malloc().

But I am confused about the second example. A pointer has been returned from format(), but I don't think I can free the buffer as I have declared it with a fixed size.

Which is the correct way to call the function? In the second example, does anything need to be freed?