Re: From wchar_t to char32_t

[Bruno Haible]

Paul Eggert wrote:
> > -      wchar_t wch;
> > -      size_t nbytes = mbrtowc (&wch, s, n, &d->mbs);
> > +      char32_t wch;
> > +      size_t nbytes = mbrtoc32 (&wch, s, n, &d->mbs);
> >        if (0 < nbytes && nbytes < (size_t) -2)
> >          {
> >            *pwc = wch;
> > +          if (nbytes == (size_t) -3)
> > +            nbytes = 0;
> >            return nbytes;
> 
> That last change doesn't match the comment for the mbs_to_wchar 
> function, which says that the function always returns a positive int. 
> Callers depend on this.
> 
> Since nbytes cannot be (size_t) -3 on any known implementation, it's not 
> surprising that this issue wasn't found by testing. And since it'll 
> likely be a hassle to port the rest of the code to purely-theoretical 
> platforms where nbytes == (size_t) -3, I suggest instead simply adding a 
> comment that nbytes cannot be (size_t) -3 there.

I have now fixed this problem like this:

@@ -640,11 +652,13 @@ mbs_to_wchar (wint_t *pwc, char const *s, idx_t n, struct 
dfa *d)
 
   if (wc == WEOF)
     {
-      wchar_t wch;
-      size_t nbytes = mbrtowc (&wch, s, n, &d->mbs);
+      char32_t wch;
+      size_t nbytes = mbrtoc32 (&wch, s, n, &d->mbs);
       if (0 < nbytes && nbytes < (size_t) -2)
         {
           *pwc = wch;
+          /* nbytes cannot be == (size) -3 here, since we rely on the
+             'mbrtoc32-regular' module.  */
           return nbytes;
         }
       memset (&d->mbs, 0, sizeof d->mbs);


And pushed the attached patch.

0001-dfa-Overcome-wchar_t-limitations.patch
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