With the const-everywhere approach, the code reads like it's in an SSA format and is dataflow-oriented. As an extreme example, the "len - 1" expression can be substituted with yet another const variable:

    const size_t len = strlen(s);
    if (len > 0)
    {
        const size_t len_minus_one = len - 1;
        s[len_minus_one] = '\0';
    }

The additional const "variables" also add another layer of self-documentation by virtue of their names.