[gcc-in-cxx] Patch: CONST_CAST2 -vs- C++

[Tom Tromey]

This patch defines CONST_CAST2 differently for C++.

This fixes a few build errors on the branch.

Ok?  (I wasn't sure whether, under the branch rules, I could approve
my own C++-ification patches.)

Tom

ChangeLog.cxx:
2008-06-21  Tom Tromey  <tromey@redhat.com>

	* system.h (CONST_CAST2): Define for C++.

Index: system.h
===================================================================
--- system.h	(revision 137020)
+++ system.h	(working copy)
@@ -786,12 +786,16 @@
    change after the fact).  Beyond these uses, most other cases of
    using this macro should be viewed with extreme caution.  */
 
+#ifdef __cplusplus
+#define CONST_CAST2(TOTYPE,FROMTYPE,X) (const_cast<TOTYPE> (X))
+#else
 #if defined(__GNUC__) && GCC_VERSION != 4000
 /* GCC 4.0.x has a bug where it may ICE on this expression.  */
 #define CONST_CAST2(TOTYPE,FROMTYPE,X) ((__extension__(union {FROMTYPE _q; TOTYPE _nq;})(X))._nq)
 #else
 #define CONST_CAST2(TOTYPE,FROMTYPE,X) ((TOTYPE)(FROMTYPE)(X))
 #endif
+#endif
 #define CONST_CAST(TYPE,X) CONST_CAST2(TYPE, const TYPE, (X))
 #define CONST_CAST_TREE(X) CONST_CAST(union tree_node *, (X))
 #define CONST_CAST_RTX(X) CONST_CAST(struct rtx_def *, (X))