Thread: Output parameter practices

Do you have any useful rules of thumb you follow when writing a function to use output parameters rather than a direct "return value?"

For example, say we have a function like this:

Code:

void util_get_string_int(const char *input, int *output)
{
    assert(input && output);
    if(!str_contains_all_digits(input))
    {
        *output = -1;
        return;
    }
    *output = atoi(input);
    return;
}

This version returns the int in an output parameter. Instead, I could just return these int values as actual ints in the return value but for this purpose, I figured I would already have an int stored in memory, so might as well just use that one.

What types of things do you consider before you make these decisions?