Retire snprintf replacement or replace with c99-snprintf

[rra]

Reported by eagle on 31 Dec 2017 20:23 UTC
The snprintf replacement from rra-c-util requires a lot of ongoing maintenance to compile cleanly with new warning options, and it's unclear that a replacement snprintf still serves any real portability objective. Systems without a working snprintf are now fairly old, and I'm considering dropping it from rra-c-util to reduce maintenance work.

Consider dropping this from INN and just requiring a working snprintf for INN to build, or if we want to keep it, replace it with c99-snprintf from https://github.com/weiss/c99-snprintf, which is being (somewhat) actively maintained. That version probably doesn't compile cleanly with all the warnings we use, but it's somewhat cleaner code.

[Julien-Elie]

Other warnings from most recent compilers:

snprintf.c:430:59: warning: cast from capability type 'char *' to non-capability, non-address type 'long' is most likely an error [-Wcapability-to-integer-cast]

                strvalue = va_arg(args, void *);
                total += fmtint(buffer, &currlen, maxlen, (long) strvalue, 16,
                                min, max, flags);

snprintf.c:786:28: warning: writing 16 bytes into a region of size 7 [-Wstringop-overflow=]

    while (leadingfrac0s-- > 0 && fplace < sizeof(fconvert))
        fconvert[fplace++] = '0';

Let's try the above suggested use of c99-snprintf replacement, and see whether it builds cleanly and has all the latest bug-fix local changes we have.