Edmund GRIMLEY EVANS wrote on 2001-05-26 13:19 UTC:
> I admit I haven't checked the latest glibc from CVS, and I haven't
> investigated any databases of bug reports, so I apologise if this is
> already well known.
>
> With glibc-2.2.3, mbrtowc(&wc, "", 0, &ps) seems to return 0 instead
> of (size_t)(-2). I think this is a bug.
It is a bug in your software. You should never call mbrtowc with 0 as
the number n of bytes that mbrtowc is allowed to examine at most. Such a
call seems useless, and the standard does not define the behaviour of
mbrtowc in that case.
One could argue - and I probably would agree - that (size_t)(-2) might
be an aesthetically more pleasing return value in that situation, but
that is not really a requirement of ISO/IEC 9899:1999(E), �7.24.6.3.2 on
page 388.
Perhaps someone should write a tutorial on common pitfalls with the
restartable multi-byte functions. The other common one is that people
try to initialize an mb_state variable with a call to
mbrtowc(NULL, "", 1, &ps). Instead, the correct (though at first glance
ugly) initialization is memset(&ps, 0, sizeof(ps)).
Markus
--
Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at acm.org, WWW: <http://www.cl.cam.ac.uk/~mgk25/>
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