Why null-terminated strings? Or: null-terminated vs. characters + length storage

Question

I'm writing a language interpreter in C, and my string type contains a length attribute, like so:

struct String
{
    char* characters;
    size_t length;
};

Because of this, I have to spend a lot of time in my interpreter handling this kind of string manually since C doesn't include built-in support for it. I've considered switching to simple null-terminated strings just to comply with the underlying C, but there seem to be a lot of reasons not to:

Bounds-checking is built-in if you use "length" instead of looking for a null.

You have to traverse the entire string to find its length.

You have to do extra stuff to handle a null character in the middle of a null-terminated string.

Null-terminated strings deal poorly with Unicode.

Non-null-terminated strings can intern more, i.e. the characters for "Hello, world" and "Hello" can be stored in the same place, just with different lengths. This can't be done with null-terminated strings.

String slice (note: strings are immutable in my language). Obviously the second is slower (and more error-prone: think about adding error-checking of begin and end to both functions).

struct String slice(struct String in, size_t begin, size_t end)
{
    struct String out;
    out.characters = in.characters + begin;
    out.length = end - begin;

    return out;
}

char* slice(char* in, size_t begin, size_t end)
{
    char* out = malloc(end - begin + 1);

    for(int i = 0; i < end - begin; i++)
        out[i] = in[i + begin];

    out[end - begin] = '\0';

    return out;
}

After all this, my thinking is no longer about whether I should use null-terminated strings: I'm thinking about why C uses them!

So my question is: are there any benefits to null-termination that I'm missing?

Answer 1

From Joel's Back to Basics:

Why do C strings work this way? It's because the PDP-7 microprocessor, on which UNIX and the C programming language were invented, had an ASCIZ string type. ASCIZ meant "ASCII with a Z (zero) at the end."

Is this the only way to store strings? No, in fact, it's one of the worst ways to store strings. For non-trivial programs, APIs, operating systems, class libraries, you should avoid ASCIZ strings like the plague.