[RFC-v4] Handle cygwin wchar_t specifics

["Pierre Muller" <pierre.muller@ics-cnrs.unistra.fr>]

> -----Message d'origine-----
> De : gdb-patches-owner@sourceware.org [mailto:gdb-patches-
> owner@sourceware.org] De la part de Tom Tromey
> Envoyé : lundi 18 avril 2011 19:18
> À : Pierre Muller
> Cc : 'Eli Zaretskii'; jan.kratochvil@redhat.com;
gdb-patches@sourceware.org
> Objet : Re: [RFA-v3] Handle cygwin wchar_t specifics
> 
> >>>>> "Pierre" == Pierre Muller <pierre.muller@ics-cnrs.unistra.fr>
writes:
> 
> Pierre>   This patch also changes the intermediate_encoding for mingw
hosts,
> Pierre>   from "wchar_t" to "UTF-16LE", but this seems to work nicely
> Pierre> for both mingw32 and mingw64 (and only if iconv is found,
> Pierre> otherwise gdb_wchar_t is simply char and phony functions are
used).
> 
> Pierre> -#define INTERMEDIATE_ENCODING host_charset ()
> Pierre> +#define DEFAULT_INTERMEDIATE_ENCODING host_charset ()
> 
> This changes the behavior if the gdb user changes the host encoding.
> This is an unusual situation, admittedly, but it seems to me that it is
> just as easy to only introduce the `intermediate_encoding' global in the
> UTF-{16,32} case.
> 
> Pierre> +  intermediate_encoding = DEFAULT_INTERMEDIATE_ENCODING;
> Pierre> +# if defined (USE_WIN32API) || defined (__CYGWIN__)
> Pierre> +  if (sizeof (gdb_wchar_t) == 2)
> Pierre> +    intermediate_encoding = "UTF-16LE";
> Pierre> +# endif
> 
> Here, instead of a special case for __CYGWIN__, and instead of
> hard-coding the endian-ness, just use the same code for all
> __STDC_ISO_10646__ platforms.  Maybe something like:
> 
> intermediate_encoding = xstrprintf ("UTF-%d%s", 8 * sizeof (wchar_t),
>                                     WORDS_BIGENDIAN ? "BE" : "LE");

  Three problems here:

1) we should really use "gdb_wchar_t" type, not "wchar_t"
2) If sizeof(gdb_wchar_t) == 1
I don't think that UTF-8LE and UTF-8BE exist, do they?
At least they are not in the iconv -l list for current cygwin.
3) WORD_BIGENDIAN is not defined at all on Cygwin,
so that your code would probably not compile.

A further question is whether UTF-32 is always supported...

Below is yet another proposal:
it transforms INTERMEDIATE_ENCODING macro into a call to
intermediate_encoding function.
This functions handles especially the case when gdb_wchar_t is 2 byte long,
by trying UTF-16XE (with X equal L or B), and if this one is not
in the list of supported charsets, tries UCS-2XE.

  As there is apparently no advantage of using UTF-32 over UCS-4 (according
to Eli)
I did not extend the change to the 4 byte case.

  Comments welcome,

Pierre Muller


2011-04-19  Pierre Muller  <muller@ics.u-strasbg.fr>

	* gdb_wchar.h (DEFAULT_INTERMEDIATE_ENCODING): New macro.
	(INTERMEDIATE_ENCODING): Change value to intermediate_encoding
	function call.
	(intermediate_encoding): New prototype.
	* charset.c (intermediate_encoding): New function.

Index: charset.c
===================================================================
RCS file: /cvs/src/src/gdb/charset.c,v
retrieving revision 1.43
diff -u -p -r1.43 charset.c
--- charset.c	11 Jan 2011 15:10:01 -0000	1.43
+++ charset.c	19 Apr 2011 09:05:43 -0000
@@ -922,6 +922,50 @@ default_auto_wide_charset (void)
   return GDB_DEFAULT_TARGET_WIDE_CHARSET;
 }
 
+#ifdef WORDS_BIGENDIAN
+#define ENDIAN_SUFFIX "BE"
+#else
+#define ENDIAN_SUFFIX "LE"
+#endif
+
+const char *
+intermediate_encoding (void)
+{
+  if (sizeof (gdb_wchar_t) == 2)
+    {
+      static const char *stored_result = NULL;
+      const char *result;
+      int i;
+
+      if (stored_result)
+	return stored_result;
+      result = "UTF-16" ENDIAN_SUFFIX;
+      /* Check that the name is in the list of handled charsets.  */
+      for (i = 0; charset_enum[i]; i++)
+	{
+	  if (strcmp (result, charset_enum[i]) == 0)
+	    {
+	      stored_result = result;
+	      return result;
+	    }
+	}
+      /* Second try, with UCS-2 type.  */
+      result = "UCS-2" ENDIAN_SUFFIX;
+      /* Check that the name is in the list of handled charsets.  */
+      for (i = 0; charset_enum[i]; i++)
+	{
+	  if (strcmp (result, charset_enum[i]) == 0)
+	    {
+	      stored_result = result;
+	      return result;
+	    }
+	}
+    }
+  /* if gdb_wchar_t is not of size 2, or if "UTF-16XE" and "UCS-2XE" are
+     not known, use DEFAULT_INTERMEDIATE_ENCODING macro.  */
+  return DEFAULT_INTERMEDIATE_ENCODING;
+}
+
 void
 _initialize_charset (void)
 {
Index: gdb_wchar.h
===================================================================
RCS file: /cvs/src/src/gdb/gdb_wchar.h,v
retrieving revision 1.6
diff -u -p -r1.6 gdb_wchar.h
--- gdb_wchar.h	1 Jan 2011 15:33:05 -0000	1.6
+++ gdb_wchar.h	19 Apr 2011 09:05:43 -0000
@@ -79,12 +79,12 @@ typedef wint_t gdb_wint_t;
    hosts that emit a BOM when the unadorned name is used.  */
 #if defined (__STDC_ISO_10646__)
 #if WORDS_BIGENDIAN
-#define INTERMEDIATE_ENCODING "UCS-4BE"
+#define DEFAULT_INTERMEDIATE_ENCODING "UCS-4BE"
 #else
-#define INTERMEDIATE_ENCODING "UCS-4LE"
+#define DEFAULT_INTERMEDIATE_ENCODING "UCS-4LE"
 #endif
 #elif defined (_LIBICONV_VERSION) && _LIBICONV_VERSION >= 0x108
-#define INTERMEDIATE_ENCODING "wchar_t"
+#define DEFAULT_INTERMEDIATE_ENCODING "wchar_t"
 #else
 /* This shouldn't happen, because the earlier #if should have filtered
    out this case.  */
@@ -115,11 +115,14 @@ typedef int gdb_wint_t;
    also providing a phony iconv, we might as well just stick with
    "wchar_t".  */
 #ifdef PHONY_ICONV
-#define INTERMEDIATE_ENCODING "wchar_t"
+#define DEFAULT_INTERMEDIATE_ENCODING "wchar_t"
 #else
-#define INTERMEDIATE_ENCODING host_charset ()
+#define DEFAULT_INTERMEDIATE_ENCODING host_charset ()
 #endif
 
 #endif
 
+#define INTERMEDIATE_ENCODING intermediate_encoding ()
+const char *intermediate_encoding (void);
+
 #endif /* GDB_WCHAR_H */