On Ubuntu 10.04, the code below prints "0 2".  This is the behavior
that I think logically makes sense (and that I was intending to
implement for OpenBSD).

However, my reading of mbsnrtowcs() description in Issue 7 is that the
correct output (assuming "en_US.UTF-8" is a valid UTF-8 based locale)
should be "0 0".

Issue 7 says:

"""
If dst is not a null pointer, the pointer object pointed to by src
shall be assigned either a null pointer (if conversion stopped due to
reaching a terminating null character) or the address just past the
last character converted (if any).
"""

However, in my test program, mbs+2 is in the *middle* of a
[multi-byte] character, not "just past" a [multi-byte] character.
Ubuntu 10.04's behavior would be consistent if the description was
"just past the last input byte consumed".

Am I misunderstanding something?  Or is there a bug in either Ubuntu
10.04's implementation or the POSIX wording?


#include <wchar.h>
#include <locale.h>
#include <string.h>
#include <stdio.h>

wchar_t wcs[100];
char mbs[100];

int main()
{
        setlocale(LC_CTYPE, "en_US.UTF-8");
        memcpy(mbs, "\xe7\x95\x8c", 4);
        const char *s = mbs;
        printf("%u ", (unsigned)mbsnrtowcs(wcs, &s, 2, 100, NULL));
        printf("%u\n", (unsigned)(s - mbs));
}