[RFA-v6] Handle cygwin wchar_t specifics

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

> > Didn't "extern" work?
> 
>   I didn't test it out before:
> it does work on my system, but is it
> sure it will compile and link correctly on
> all C compilers used for GDB?
> 
>   There is apparently no trace of your_gdb_wchar_t_is_bogus
> in my charset.o object file once it is made external.
> 
>   Could someone confirm that this will also compile
> on other C compiler used without creating link failures?
> 
> I am perfectly willing to change this but it seemed
> to me to rely on some "obscure C compiler feature"
> (don't forget that I learned C to be able to support pascal
> language in GDB...).

   I am stupid..
of course this works, otherwise each object would contain the
thousands of externals defined in all the loaded headers...

  Here is a new version,
with both static to external switch for you_gdb_wchar_t_is_bogus
and Tom latest comments.

  As it is not exactly what Tom asked me to change,
I resubmit it anyhow.
 
 Pierre

PS: Should that be included in 7.3 branch?


2011-04-21  Pierre Muller  <muller@ics.u-strasbg.fr>

	* gdb_wchar.h (USE_INTERMEDIATE_ENCODING_FUNCTION): New macro.
	(INTERMEDIATE_ENCODING): Change value to intermediate_encoding
	function call if __STDC_ISO_10646__ macro is defined.
	(intermediate_encoding): New prototype.
	* charset.c (your_gdb_wchar_t_is_bogus): New extern test variable
	to generate compile time error for unsupported gdb_wchar_t size.
	(ENDIAN_SUFFIX): New macro.
	(intermediate_encoding): New function.
	

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	21 Apr 2011 07:09:52 -0000
@@ -78,11 +78,10 @@ typedef wint_t gdb_wint_t;
    iconv_open.  We put the endianness into the encoding name to avoid
    hosts that emit a BOM when the unadorned name is used.  */
 #if defined (__STDC_ISO_10646__)
-#if WORDS_BIGENDIAN
-#define INTERMEDIATE_ENCODING "UCS-4BE"
-#else
-#define INTERMEDIATE_ENCODING "UCS-4LE"
-#endif
+#define USE_INTERMEDIATE_ENCODING_FUNCTION
+#define INTERMEDIATE_ENCODING intermediate_encoding ()
+const char *intermediate_encoding (void);
+
 #elif defined (_LIBICONV_VERSION) && _LIBICONV_VERSION >= 0x108
 #define INTERMEDIATE_ENCODING "wchar_t"
 #else
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	21 Apr 2011 07:09:52 -0000
@@ -922,6 +922,70 @@ default_auto_wide_charset (void)
   return GDB_DEFAULT_TARGET_WIDE_CHARSET;
 }
 
+
+#ifdef USE_INTERMEDIATE_ENCODING_FUNCTION
+/* Macro used for UTF or UCS endianness suffix.  */
+#if WORDS_BIGENDIAN
+#define ENDIAN_SUFFIX "BE"
+#else
+#define ENDIAN_SUFFIX "LE"
+#endif
+
+/* The code below serves to generate a compile time error if
+   gdb_wchar_t type is not of size 2 nor 4, despite the fact that
+   macro __STDC_ISO_10646__ is defined.
+   This is better than a gdb_assert call, because GDB cannot handle
+   strings correctly if this size is different.  */
+
+extern char your_gdb_wchar_t_is_bogus[(sizeof (gdb_wchar_t) == 2
+				       || sizeof (gdb_wchar_t) == 4)
+				      ? 1 : -1];
+
+/* intermediate_encoding returns the charset unsed internally by
+   GDB to convert between target and host encodings. As the test above
+   compiled, sizeof (gdb_wchar_t) is either 2 or 4 bytes.
+   UTF-16/32 is tested first, UCS-2/4 is tested as a second option,
+   otherwise an error is generated.  */
+
+const char *
+intermediate_encoding (void)
+{
+  iconv_t desc;
+  static const char *stored_result = NULL;
+  char *result;
+  int i;
+
+  if (stored_result)
+    return stored_result;
+  result = xstrprintf ("UTF-%d%s", sizeof (gdb_wchar_t) * 8,
ENDIAN_SUFFIX);
+  /* Check that the name is supported by iconv_open.  */
+  desc = iconv_open (result, host_charset ());
+  if (desc != (iconv_t) -1)
+    {
+      iconv_close (desc);
+      stored_result = result;
+      return result;
+    }
+  /* Not valid, free the allocated memory.  */
+  xfree (result);
+  /* Second try, with UCS-2 type.  */
+  result = xstrprintf ("UCS-%d%s", sizeof (gdb_wchar_t), ENDIAN_SUFFIX);
+  /* Check that the name is supported by iconv_open.  */
+  desc = iconv_open (result, host_charset ());
+  if (desc != (iconv_t) -1)
+    {
+      iconv_close (desc);
+      stored_result = result;
+      return result;
+    }
+  /* Not valid, free the allocated memory.  */
+  xfree (result);
+  /* No valid charset found, generate error here.  */
+  error (_("Unable to find a vaild charset for string conversions"));
+}
+
+#endif /* USE_INTERMEDIATE_ENCODING_FUNCTION */
+
 void
 _initialize_charset (void)
 {