Re: crash in newlocale()

[Takashi Yano <takashi.yano@nifty.ne.jp>]

On Thu, 11 Aug 2022 12:29:31 -0400
Ken Brown wrote:
> On 8/11/2022 8:18 AM, Takashi Yano wrote:
> > On Thu, 11 Aug 2022 11:29:28 +1000
> > Tony Cook wrote:
> >> $ cat newlocale-test.c
> >> #include <locale.h>
> >> #include <stdio.h>
> >>
> >> int main() {
> >>    locale_t st = newlocale(LC_ALL_MASK, "C", (locale_t)0);
> >>
> >>    locale_t st2 = newlocale(LC_CTYPE_MASK, "en_US.UTF-8", st);
> >>    printf("Done\n");
> >>    return 0;
> >> }
> >> Program terminated with signal SIGTRAP, Trace/breakpoint trap.
> >> The program no longer exists.
> >> (gdb)
> > 
> > I looked into this problem and found the access violation
> > occurs at:
> > newlib/libc/locale/newlocale.c
> > @@ 188,7 @@ _newlocale_r (struct _reent *p, int category_mask, const char *locale,
> > 	if (tmp_locale.lc_cat[i].buf == (const void *) -1)
> > 	  {
> > 	    tmp_locale.lc_cat[i].buf = base->lc_cat[i].buf;
> > 	    base->lc_cat[i].ptr = base->lc_cat[i].buf = NULL; <-- Here!!!
> > 	  }
> > #endif /* __HAVE_LOCALE_INFO__ */
> >        _freelocale_r (p, base);
> > 
> > This is because
> > locale_t st = newlocale(LC_ALL_MASK, "C", (locale_t)0);
> > returns
> >    extern const struct __locale_t __C_locale;
> >    return (struct __locale_t *) &__C_locale;
> > , which is in the const area that cannot be modified.
> > 
> > This seems to be a newlib bug.
> > 
> > I also found following patch solves the issue.
> > 
> > diff --git a/newlib/libc/locale/newlocale.c b/newlib/libc/locale/newlocale.c
> > index 0789d5fd9..1974665ec 100644
> > --- a/newlib/libc/locale/newlocale.c
> > +++ b/newlib/libc/locale/newlocale.c
> > @@ -108,10 +108,12 @@ _newlocale_r (struct _reent *p, int category_mask, const char *locale,
> >       }
> >     /* If the new locale is supposed to be all default locale, just return
> >        a pointer to the default locale. */
> > +#if 0
> >     if ((!base && category_mask == 0)
> >         || (category_mask == LC_VALID_MASK
> >   	  && (!strcmp (locale, "C") || !strcmp (locale, "POSIX"))))
> >       return __get_C_locale ();
> > +#endif
> >     /* Start with setting all values to the default locale values. */
> >     tmp_locale = *__get_C_locale ();
> >     /* Fill out new category strings. */
> 
> Good work tracking this down!
> 
> I was about to suggest that instead of just disabling this optimization, you 
> call _duplocale_r to return a duplicate of __get_C_locale ().  But then I saw 
> the following in the definition of _duplocale_r in duplocale.c:
> 
>    /* The "C" locale is used statically, never copied. */
>    else if (locobj == __get_C_locale ())
>      return __get_C_locale ();
> 
> This looks like another bug.  Shouldn't duplocale always return a modifiable object?

Thanks!
Corinna's patch avoids the problem also for this case.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>