strlcpy()

Feel free to use strlcpy() exclusively yourself, but don't tell everyone
else what they can or can't use. The only function I have ever agreed
with removing is gets() because there is a nearly 100% chance of a bug
every time it is used.

However, it is NOT in glibc, because Ulrich Drepper doesn't want it in there. You can see his rationale for this in the glibc mailing list.

I don't agree with his decision. One of the biggest security problems is STILL buffer overflows, and strlcpy()/strlcat() can really help reduce their incidence. And since it's not in glibc, everyone has to "roll their own" implementation (which may not be as efficient as it would be if it were in the standard library). If a future C standard included strlcpy() in the standard C library, then I believe glibc would add it too. Thus, if you want strlcpy() available everywhere, it might be best to appear to the ISO C group to add strlcpy() and strlcat() to the C standard library.

size_t strlcpy(char *dest, const char *src, size_t n)
{
        int len, i;

        if (!n)
                return 0;

        len = strlen(src);
        if (len >= n)
                len = n - 1;

        /* check for overlapping source and destination */
        if ((src < dest && src + len >= dest)
                || (dest < src && dest + n > src)
                || src == dest)
        {
                size_t i;

                for (i = 0; src[i] && i < n - 1; i++)
                        dest[i] = src[i];

                dest[i] = (char) 0;
        }
        else
        {
                memcpy(dest, src, len);
                dest[len] = (char) 0;
        }

        return len;
}

I haven't tested this extensively, but I've found that the best way to debug code is to post it on the internet. ;-) People come out of the woodwork...

I wonder if we should bother about what to do if size == 0. Mine crashes spectacularly, which is a Good Thing.

Getting within 15% of memcpy is pretty damn good, in my estimation. Of course I didn't read Linus's version, or OpenBSD's; that would be cheating, and I would be tainted besides. Of course now that I have been told, via cleanroom methods, I can adjust mine to be equally fast, and maybe (one can hope) actually identical to both Linus's and OpenBSD's.