[PATCH 3/3] fhandler_pty_slave::setup_locale: respect charset == "UTF-8"

[Corinna Vinschen]

On Sep  2 19:54, Takashi Yano via Cygwin-patches wrote:
> Hi Corinna,
> 
> On Wed, 2 Sep 2020 10:38:18 +0200
> Corinna Vinschen wrote:
> > On Sep  2 10:30, Corinna Vinschen wrote:
> > > Ok guys, I'm not opposed to this change in terms of its result,
> > > but I'm starting to wonder why all this locale code in fhandler_tty
> > > is necessary at all.
> > > 
> > > I see that get_langinfo() calls __loadlocale and performs a lot of stuff
> > > on the charsets which looks like duplicates of the initial_setlocale()
> > > call performed at DLL startup.
> > > 
> > > If there's anything missing in the initial_setlocale() call which would
> > > be required by the pseudo tty code?  What exactly is it?  The codepage?
> > > And why can't we just add the info to cygheap->locale at initial_setlocale()
> > > time so it's available at exec time without going through all this hassle
> > > every time?
> > > 
> > > Apart from that, all this locale/charset/lcid stuff should be concentrated
> > > in nlsfunc.cc ideally.
> > 
> > get_locale_from_env() and get_langinfo() should go away.  If we just
> > need a codepage for get_ttyp ()->term_code_page, we should really find a
> > way to do this from within internal_setlocale().
> 
> I looked into internal_setlocale() code, but I could not found
> the code which handles thecode page. I found the code handling
> the code page in __set_charset_from_locale() function in nlsfuncs.cc,
> but it does not return code page itself. Could you please explain
> more detail of your idea?

I had none yet :)  I was just musing, without actually thinking about a
solution.  But I think this isn't very complicated.  Given this is
inside Cygwin, nothing keeps the function to have a well-defined
side-effect, as in setting a (not yet existing) member "term_code_page"
of cygheap->locale.

Kind of like this:

diff --git a/winsup/cygwin/cygheap.h b/winsup/cygwin/cygheap.h
index 8877cc358c39..2b84f4252071 100644
--- a/winsup/cygwin/cygheap.h
+++ b/winsup/cygwin/cygheap.h
@@ -341,6 +341,7 @@ struct cygheap_debug
 struct cygheap_locale
 {
   mbtowc_p mbtowc;
+  UINT term_code_page;
 };
 
 struct user_heap_info
diff --git a/winsup/cygwin/nlsfuncs.cc b/winsup/cygwin/nlsfuncs.cc
index 668d7eb9e778..752f4239d911 100644
--- a/winsup/cygwin/nlsfuncs.cc
+++ b/winsup/cygwin/nlsfuncs.cc
@@ -1298,6 +1298,9 @@ __set_charset_from_locale (const char *locale, char *charset)
 			    LOCALE_IDEFAULTANSICODEPAGE | LOCALE_RETURN_NUMBER,
 			    (PWCHAR) &cp, sizeof cp))
     cp = 0;
+  /* Store codepage in cygheap->locale so fhandler_tty can switch the
+     pseudo console to the correct codepage. */
+  cygheap->locale.term_code_page = cp ?: CP_UTF8;
   /* Translate codepage and lcid to a charset closely aligned with the default
      charsets defined in Glibc. */
   const char *cs;

Make sense?


Thanks,
Corinna