[Bug libc/29913] iconv(3) is not POSIX compliant, and does not conform to linux man-pages manual

["steffen at sdaoden dot eu" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=29913

--- Comment #6 from Steffen Nurpmeso <steffen at sdaoden dot eu> ---
Do not know how to relate (unless you did by noting).

Linux man says

  The conversion can stop for four reasons

then the only thing that may match is

  An invalid multibyte sequence is encountered in the input

and that is not what is going on.
It is not an invalid input.

And no, iconv users surely always have to be prepared for a loop i would say,
just in case the input has a problem and needs to be replaced with a
replacement character.

That gnulib snippet is terrible.  I have such a thing also in order to be able
to perform an iconv test (we pass through what the lib does).
For example, this snippet was in the program i took maintainership over before
2004:


/*
 * Fault-tolerant iconv() function.
 */
static size_t
iconv_ft(iconv_t cd, char **inb, size_t *inbleft, char **outb, size_t
*outbleft)
{
        size_t sz = 0;

        while ((sz = iconv(cd, inb, inbleft, outb, outbleft)) == (size_t)-1
                        && (errno == EILSEQ || errno == EINVAL)) {
                if (*inbleft > 0) {
                        (*inb)++;
                        (*inbleft)--;
                } else {
                        **outb = '\0';
                        break;
                }
                if (*outbleft > 0) {
                        *(*outb)++ = '?';
                        (*outbleft)--;
                } else {
                        **outb = '\0';
                        break;
                }
        }
        return sz;
}

Instead GNU should have reused the EINVAL error for this case.  Or IO, NODATA,
NOENT, NOMSG, NOTSUP, NOSYS, NOTOBACCO.

Anyhow, that gnulib snippet was a shock.  What a mess.

The problem with the GNU approach is that portable software that glues to the
POSIX standard and/or reads the Linux manual has to perform a lot of checks in
order to find out whether the native iconv supports / wants //TRANSLIT to get
the behaviour that the standard describes.

At least in my opinion.
And, as you say, all others but GNU follow this.

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