[Bug libc/9674] New: mbtowc keeps internal state even for stateless encodings

[Bug libc/9674] New: mbtowc keeps internal state even for stateless encodings

[bruno at clisp dot org]

Run the following program on a system with a fr_FR.UTF-8 locale.
===================================================================
#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <wchar.h>

int main ()
{
  int locale_found = setlocale (LC_ALL, "fr_FR.UTF-8") != NULL;
  printf ("%d\n", locale_found);

  printf ("%d\n", mbtowc (NULL, NULL, 0));

  static const char input[4] = { 195, 188, 195, 159 };
  wchar_t wc;

  int res2a = mbtowc (&wc, input, 4);
  printf ("%d\n", res2a);

  int res1 = mbtowc (&wc, input, 1);
  printf ("%d\n", res1);

  int res2b = mbtowc (&wc, input, 4);
  printf ("%d\n", res2b);

  return 0;
}
===================================================================
$ gcc -O -Wall foo.c
$ ./a.out 
1
0
2
-1
-1

Expected output:

1
0
2
-1
2

Rationale:
The first line shows that the locale was correctly set. So the locale encoding
is UTF-8.
The second line that the UTF-8 encoding is non state dependent.
The third and fifth line show that the same call has different results, that
is, it must depend on a hidden state.
But the mbtowc specification says that "For a state-dependent encoding ...
Subsequent calls with s as other than a null pointer shall cause the internal 
state of the function to be altered as necessary."
However, the encoding in use here is not state dependent. Hence the function's
results should not depend on hidden state.

Reference:
POSIX:2008 specification of mbtowc:
<http://www.opengroup.org/onlinepubs/9699919799/functions/mbtowc.html>

-- 
           Summary: mbtowc keeps internal state even for stateless encodings
           Product: glibc
           Version: 2.8
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: bruno at clisp dot org
                CC: glibc-bugs at sources dot redhat dot com
 GCC build triplet: i686-suse-linux
  GCC host triplet: i686-suse-linux
GCC target triplet: i686-suse-linux


http://sourceware.org/bugzilla/show_bug.cgi?id=9674

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[Bug libc/9674] mbtowc keeps internal state even for stateless encodings

[bonzini at gnu dot org]

------- Additional Comments From bonzini at gnu dot org  2008-12-22 10:14 -------
For completeness, I will add that this requirement is also present in ISO C at
the beginning of 7.20.7 (outside 7.20.7.2 which is where mbtowc is defined).

OTOH, the fact that "For a state-dependent encoding, each function is placed
into its initial state by a call for which its character pointer argument, s, is
a null pointer" does not imply that an implementation cannot do the same for
state-independent encodings too...


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bonzini at gnu dot org


http://sourceware.org/bugzilla/show_bug.cgi?id=9674

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[Bug libc/9674] mbtowc keeps internal state even for stateless encodings

[drepper at redhat dot com]

------- Additional Comments From drepper at redhat dot com  2008-12-26 18:54 -------
The state does not only contain the shift state but also incomplete input.  That
explains the behavior and it is a correct implementation according to the
wording of the specification.

You'll have to get the standard body to explicitly confirm your reading before
anything will be changed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING


http://sourceware.org/bugzilla/show_bug.cgi?id=9674

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[Bug libc/9674] mbtowc keeps internal state even for stateless encodings

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=9674

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
              Flags|                            |security-

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[Bug libc/9674] mbtowc keeps internal state even for stateless encodings

[schwab at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=9674

Andreas Schwab <schwab at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|jackie.rosen at hushmail dot com   |

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[Bug libc/9674] mbtowc keeps internal state even for stateless encodings

[jackie.rosen at hushmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=9674

Jackie Rosen <jackie.rosen at hushmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jackie.rosen at hushmail dot com

--- Comment #4 from Jackie Rosen <jackie.rosen at hushmail dot com> ---
*** Bug 260998 has been marked as a duplicate of this bug. ***
Seen from the domain http://volichat.com
Page where seen: http://volichat.com/adult-chat-rooms
Marked for reference. Resolved as fixed @bugzilla.

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[Bug libc/9674] mbtowc keeps internal state even for stateless encodings

[drepper.fsp at gmail dot com]

http://sourceware.org/bugzilla/show_bug.cgi?id=9674

Ulrich Drepper <drepper.fsp at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |INVALID

--- Comment #3 from Ulrich Drepper <drepper.fsp at gmail dot com> 2011-05-16 00:10:38 UTC ---
I'm closing this now.  The "state object" as meant to be used like this. 
"State" as in stateful is something else.

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