Re: Your INTERMEDIATE_ENCODING patch for Solaris

[Tom Tromey <tromey at redhat dot com>]

>>>>> "Tom" == Tom Tromey <tromey@redhat.com> writes:

Kazu> As Andrew replied to your message above, __STDC_ISO_10646__ is not
Kazu> defined on Solaris.  Could we use __sun__ instead?

Tom> I am not a Solaris expert, but some digging through the online
Tom> OpenSolaris libc sources a few months ago convinced me that the Solaris
Tom> wchar_t is in fact not UCS-4.

Tom> If that is true, then this patch would be incorrect.

While looking at this more today, I found:

    http://defect.opensolaris.org/bz/show_bug.cgi?id=11076

Some of the comments make it clear that wchar_t != UCS-4 for Solaris.

Tom> This particular problem has come up multiple times.  I am not completely
Tom> sure what to do about it, but my current inclination is to change gdb so
Tom> that most hosts fall back to PHONY_ICONV, with exceptions for libiconv
Tom> and for Linux.  This will at least have gdb default to working, and is
Tom> also attractive because I have some hope of actually testing it.

Daniel> Sounds good to me.

Here is what I am testing.  If someone can try it out on Solaris, I
would appreciate that.

Tom

b/gdb/ChangeLog:
2010-08-17  Tom Tromey  <tromey@redhat.com>

	* gdb_wchar.h: Check HAVE_LIBICONV, __STDC_ISO_10646__.  Change
	how INTERMEDIATE_ENCODING is defined.
	* configure, config.in: Rebuild.
	* acinclude.m4 (AM_ICONV): Define HAVE_LIBICONV.

diff --git a/gdb/acinclude.m4 b/gdb/acinclude.m4
index 1942ef4..082a9bc 100644
--- a/gdb/acinclude.m4
+++ b/gdb/acinclude.m4
@@ -256,6 +256,7 @@ AC_DEFUN([AM_ICONV],
   LIBICONV=
   if test "$am_cv_lib_iconv" = yes; then
     LIBICONV="-liconv"
+    AC_DEFINE(HAVE_LIBICONV, 1, [Define if using libiconv.])
   else
     LIBICONV_LIBDIR=
     LIBICONV_INCLUDE=
diff --git a/gdb/config.in b/gdb/config.in
index 7659181..35272a2 100644
--- a/gdb/config.in
+++ b/gdb/config.in
@@ -214,6 +214,9 @@
 /* Define if you have the expat library. */
 #undef HAVE_LIBEXPAT
 
+/* Define if using libiconv. */
+#undef HAVE_LIBICONV
+
 /* Define to 1 if you have the `libiconvlist' function. */
 #undef HAVE_LIBICONVLIST
 
diff --git a/gdb/configure b/gdb/configure
index 485c904..852c5c1 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -9450,6 +9450,9 @@ $as_echo "$am_cv_func_iconv" >&6; }
   LIBICONV=
   if test "$am_cv_lib_iconv" = yes; then
     LIBICONV="-liconv"
+
+$as_echo "#define HAVE_LIBICONV 1" >>confdefs.h
+
   else
     LIBICONV_LIBDIR=
     LIBICONV_INCLUDE=
diff --git a/gdb/gdb_wchar.h b/gdb/gdb_wchar.h
index fca3fe4..1ff7a1c 100644
--- a/gdb/gdb_wchar.h
+++ b/gdb/gdb_wchar.h
@@ -23,7 +23,11 @@
    
    Capable systems have the full suite: wchar_t support and iconv
    (perhaps via GNU libiconv).  On these machines, full functionality
-   is available.
+   is available.  Note that full functionality is dependent on us
+   being able to convert from an arbitrary encoding to wchar_t.  In
+   practice this means we look for __STDC_ISO_10646__ (where we know
+   the name of the wchar_t encoding) or GNU libiconv, where we can use
+   "wchar_t".
    
    DJGPP is known to have libiconv but not wchar_t support.  On
    systems like this, we use the narrow character functions.  The full
@@ -35,8 +39,6 @@
    wrappers for the wchar_t functionality we use.  */
 
 
-#define INTERMEDIATE_ENCODING "wchar_t"
-
 #if defined (HAVE_ICONV)
 #include <iconv.h>
 #else
@@ -45,9 +47,11 @@
 #define PHONY_ICONV
 #endif
 
-/* We use "btowc" as a sentinel to detect functioning wchar_t
-   support.  */
-#if defined (HAVE_ICONV) && defined (HAVE_WCHAR_H) && defined (HAVE_BTOWC)
+/* We use "btowc" as a sentinel to detect functioning wchar_t support.
+   We check for either __STDC_ISO_10646__ or libiconv in order to
+   ensure we can convert to and from wchar_t.  */
+#if defined (HAVE_ICONV) && defined (HAVE_WCHAR_H) && defined (HAVE_BTOWC) \
+  && (defined (__STDC_ISO_10646__) || defined (HAVE_LIBICONV))
 
 #include <wchar.h>
 #include <wctype.h>
@@ -63,6 +67,25 @@ typedef wint_t gdb_wint_t;
 
 #define LCST(X) L ## X
 
+/* If __STDC_ISO_10646__ is defined, then the host wchar_t is UCS-4.
+   We exploit this fact in the hope that there are hosts that define
+   this but which do not support "wchar_t" as an encoding argument to
+   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
+#elif defined (HAVE_LIBICONV)
+#define INTERMEDIATE_ENCODING "wchar_t"
+#else
+/* This shouldn't happen, because the earlier #if should have filtered
+   out this case.  */
+#error "Neither __STDC_ISO_10646__ nor HAVE_LIBICONV defined"
+#endif
+
 #else
 
 typedef char gdb_wchar_t;