re PR c++/7598 (offsetof broken)

cp:
	PR c++/7598
	* typeck.c (build_unary_op): Fold offsetof idiom. Fixes
	regression caused by my 2002-08-08 patch.
testsuite:
	* g++.dg/other/offsetof1.C: New test

From-SVN: r56346

gcc/cp/ChangeLog

+2002-08-15  Nathan Sidwell  <nathan@codesourcery.com>
+
+	PR c++/7598
+	* typeck.c (build_unary_op): Fold offsetof idiom. Fixes
+	regression caused by my 2002-08-08 patch.
+
 2002-08-13  Mark Mitchell  <mark@codesourcery.com>
 
 	* decl.c (pushdecl_class_level): Honor requests to bind names to

gcc/cp/typeck.c

@@ -4256,6 +4256,24 @@ build_unary_op (code, xarg, noconvert)
 		   TREE_OPERAND (arg, 1));
 	    return error_mark_node;
 	  }
+	else if (TREE_CODE (arg) == COMPONENT_REF
+		 && TREE_CODE (TREE_OPERAND (arg, 0)) == INDIRECT_REF
+		 && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (arg, 0), 0))
+		     == INTEGER_CST))
+	  {
+	    /* offsetof idiom, fold it. */
+	    tree field = TREE_OPERAND (arg, 1);
+	    tree rval = build_unary_op (ADDR_EXPR, TREE_OPERAND (arg, 0), 0);
+	    tree binfo = lookup_base (TREE_TYPE (TREE_TYPE (rval)),
+				      decl_type_context (field),
+				      ba_check, NULL);
+	    
+	    rval = build_base_path (PLUS_EXPR, rval, binfo, 1);
+	    rval = build1 (NOP_EXPR, argtype, rval);
+	    TREE_CONSTANT (rval) = TREE_CONSTANT (TREE_OPERAND (rval, 0));
+	    addr = fold (build (PLUS_EXPR, argtype, rval,
+				cp_convert (argtype, byte_position (field))));
+	  }
 	else
 	  addr = build1 (ADDR_EXPR, argtype, arg);
 

gcc/testsuite/ChangeLog

+2002-08-15  Nathan Sidwell  <nathan@codesourcery.com>
+
+	* g++.dg/other/offsetof1.C: New test.
+
 2002-08-14  Richard Henderson  <rth@redhat.com>
 
 	* gcc.dg/tls/diag-3.c: Fix expected message strings.

gcc/testsuite/g++.dg/other/offsetof1.C

+// { dg-do compile }
+
+// Copyright (C) 2002 Free Software Foundation, Inc.
+// Contributed by Nathan Sidwell 14 Aug 2002 <nathan@codesourcery.com>
+
+// PR c++ 7598, offsetof broke
+
+struct F
+{
+  char i;
+  char j;
+};
+
+static int ary[((unsigned) &((struct F *)0)->j)];