BUG REPORT: glibc 2.2 mbrtowc() fails to decode final byte

[Markus Kuhn]

The following regression test fails in glibc 2.2 under linux-i386:

-------------------------------------------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include <wchar.h>
#include <locale.h>

int main() {

  // UTF-8 single byte feeding test for mbrtowc()
  wchar_t wc;
  mbstate_t s;
  char *locale = "en_GB.UTF-8";
 
  if (!setlocale(LC_CTYPE,locale)) {
    fprintf(stderr, "locale '%s' not available!\n", locale);
    exit(1);
  }
  wc = 42; /* arbitrary number */
  assert(mbrtowc(NULL, NULL, 0, &s) == 0);   /* get s into initial state */
  assert(mbrtowc(&wc, "", 1, &s) == 0);  /* test final byte processing */
  assert(wc == 0);  /* test final byte decoding */

  return 0;
}
-------------------------------------------------------------------

The tested behaviour is clearly required by ISO/IEC 9899:1999:

       7.24.6.3.2  The mbrtowc function

       [...]

       [#4] The mbrtowc function returns the first of the following
       that applies (given the current conversion state):

       0               if the next n or fewer  bytes  complete  the
                       multibyte  character that corresponds to the
                       null wide  character  (which  is  the  value
                                              ^^^^^^^^^^^^^^^^^^^^^
                       stored).
                       ^^^^^^

This was first reported by Edmund GRIMLEY EVANS on 2000-11-11.

Markus

-- 
Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at acm.org,  WWW: <http://www.cl.cam.ac.uk/~mgk25/>