Re: Bug in mbsrtowcs?

[Jeff Johnston <jjohnstn at redhat dot com>]

Corinna Vinschen wrote:
> On Feb 13 14:36, Jeff Johnston wrote:
>   
> > Corinna Vinschen wrote:
> >     
> > > Hang on.  If _mbrtowc_r encounters an incomplete MB char then it does
> > > not form an invalid character so there's no reason to return with -1 and
> > > set errno to EILSEQ.  However, it also doesn't form a *valid* character,
> > > it's just incomplete.  Thus it must be the start of the last character
> > > at the end of the input string.
> > >
> > >   
> > >       
> > This code is there because it means that the character has redundant shift 
> > state.  From mbrtowc:
> >
> > (*size_t*)-2
> >    If the next /n/ bytes contribute to an incomplete but potentially
> >    valid character, and all /n/ bytes have been processed (no value is
> >    stored). When /n/ has at least the value of the {MB_CUR_MAX} macro,
> >    this case can only occur if /s/ points at a sequence of redundant
> >    shift sequences (for implementations with state-dependent encodings).
> >
> > In our case, n is MB_CUR_MAX so it must be redundant shift sequence.  The 
> > state is stored so if we increase the src pointer, it should continue where 
> > it left off.
> >     
>
> Uhh, that was what I was missing, now I understand.  However, it's still
> at the end of the string so we can return from the function at this
> point.
>
>   
No, it isn't at the end of the string.  It has processed all MB_CUR_MAX 
bytes we asked it to successfully and not completed the character.  The 
reason is that there are stupid shift states added (e.g. Out In Out 
which eats up extra bytes without doing anything and so if we only ask 
it to process MB_CUR_MAX bytes we don't see the end of the last shift 
sequence).   End of string will cause a different error.  Does that 
explain it better?
> In this case the equivalent expression in the new mbsnrtowcs_r
> changes to
>
>   else if (bytes == -2)
>     {
>       *src += nms;
>       return count;
>     }
>
> Shall I send a new patch for the mbsnrtowcs.c file?
>
>
> Corinna
>
>