gcc toplevel:

	* expr.c (store_constructor): Clear union if constructor is empty.
cp:
	* typeck2.c (process_init_constructor): Handle empty constructors.
testsuite:
	* g++.old-deja/g++.other/union2.C: New test.

From-SVN: r29956

gcc/ChangeLog

+Wed Oct 13 22:01:35 1999  J"orn Rennecke <amylaar@cygnus.co.uk>
+
+	* expr.c (store_constructor): Clear union if constructor is empty.
+
 Wed Oct 13 15:19:04 1999  Jim Wilson  <wilson@cygnus.com>
 
 	* config/rs6000/sysv4.h (CC1_SPEC): Fix errors from Jan 19 change.

gcc/cp/ChangeLog

+Wed Oct 13 22:01:35 1999  J"orn Rennecke <amylaar@cygnus.co.uk>
+
+	* typeck2.c (process_init_constructor): Handle empty constructors.
+
 1999-10-13  Jason Merrill  <jason@yorick.cygnus.com>
 
 	* decl.c (lang_mark_tree): Mark NAMESPACE_LEVEL.

gcc/cp/typeck2.c

@@ -921,7 +921,9 @@ process_init_constructor (type, init, elts)
 	  members = expr_tree_cons (field, next1, members);
 	}
     }
-  else if (TREE_CODE (type) == UNION_TYPE)
+  else if (TREE_CODE (type) == UNION_TYPE
+	   /* If the initializer was empty, use default zero initialization.  */
+	   && tail)
     {
       register tree field = TYPE_FIELDS (type);
 

gcc/expr.c

@@ -4073,7 +4073,14 @@ store_constructor (exp, target, align, cleared)
       /* Inform later passes that the whole union value is dead.  */
       if (TREE_CODE (type) == UNION_TYPE
 	  || TREE_CODE (type) == QUAL_UNION_TYPE)
-	emit_insn (gen_rtx_CLOBBER (VOIDmode, target));
+	{
+	  emit_insn (gen_rtx_CLOBBER (VOIDmode, target));
+
+	  /* If the constructor is empty, clear the union.  */
+	  if (! CONSTRUCTOR_ELTS (exp)  && ! cleared)
+	    clear_storage (target, expr_size (exp),
+			   TYPE_ALIGN (type) / BITS_PER_UNIT);
+	}
 
       /* If we are building a static constructor into a register,
 	 set the initial value as zero so we can fold the value into

gcc/testsuite/ChangeLog

+Wed Oct 13 22:01:35 1999  J"orn Rennecke <amylaar@cygnus.co.uk>
+
+	* g++.old-deja/g++.other/union2.C: New test.
+
 1999-10-13  Nathan Sidwell  <nathan@acm.org>
 
 	* g++.old-deja/g++.other/vaarg2.C: New test.

gcc/testsuite/g++.old-deja/g++.other/union2.C

+// Bug: g++ crashed on empty intializers for unions.
+// Bug: gcc and g++ didn't zero unions with empty initializers.
+// Submitted by J"orn Rennecke <amylaar@cygnus.co.uk>
+
+typedef union u
+{
+  union u *up;
+  void *vp;
+} u;
+
+static u v = {};
+
+void bar (u);
+void baz (u);
+
+void foo()
+{
+       u w = {};
+       u x = { &v };
+       baz (x);
+       bar (w);
+}
+
+void baz (u w) { }
+
+void bar (u w)
+{
+  if (w.up)
+    exit (1);
+}
+
+int main ()
+{
+  foo ();
+  return 0;
+}