From patchwork Mon Oct 22 22:45:03 2012
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Subject: [C++] PR 54922
Date: Mon, 22 Oct 2012 12:45:03 -0000
From: Paolo Carlini <paolo.carlini@oracle.com>
X-Patchwork-Id: 193298
Message-Id: <5085CC6F.8000908@oracle.com>
To: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>
Cc: Jason Merrill <jason@redhat.com>

Hi,

today I spent quite a bit of time on this reject legal issue filed by 
Daniel, having to do with constrexpr constructors and anonymous union 
members: I didn't want to make the loop much more complex but we have to 
handle correctly multiple anonymous union too and of course produce 
correct diagnostics in all cases (eg, together with multiple members 
initialization diagnostics too). I figured out the below. Tested 
x86_64-linux, as usual.

Thanks,
Paolo.

////////////////////////
/cp
2012-10-22  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/54922
	* semantics.c (cx_check_missing_mem_inits): Handle anonymous union
	members.

/testsuite
2012-10-22  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/54922
	* g++.dg/cpp0x/constexpr-union4.C: New.


Index: testsuite/g++.dg/cpp0x/constexpr-union4.C
===================================================================
--- testsuite/g++.dg/cpp0x/constexpr-union4.C	(revision 0)
+++ testsuite/g++.dg/cpp0x/constexpr-union4.C	(working copy)
@@ -0,0 +1,13 @@
+// PR c++/54922
+// { dg-do compile { target c++11 } }
+
+class nullable_int
+{
+  bool init_;
+  union {
+    unsigned char for_value_init;
+    int value_;
+  };
+public:
+  constexpr nullable_int() : init_(false), for_value_init() {}
+};
Index: cp/semantics.c
===================================================================
--- cp/semantics.c	(revision 192692)
+++ cp/semantics.c	(working copy)
@@ -6139,17 +6139,23 @@ cx_check_missing_mem_inits (tree fun, tree body, b
   for (i = 0; i <= nelts; ++i)
     {
       tree index;
+      tree anon_union_init_type = NULL_TREE;
       if (i == nelts)
 	index = NULL_TREE;
       else
 	{
 	  index = CONSTRUCTOR_ELT (body, i)->index;
+	  /* Handle anonymous union members.  */
+	  if (TREE_CODE (index) == COMPONENT_REF
+	      && ANON_UNION_TYPE_P (TREE_TYPE (TREE_OPERAND (index, 0))))
+	    anon_union_init_type = TREE_TYPE (TREE_OPERAND (index, 0));
 	  /* Skip base and vtable inits.  */
-	  if (TREE_CODE (index) != FIELD_DECL
-	      || DECL_ARTIFICIAL (index))
+	  else if (TREE_CODE (index) != FIELD_DECL
+		   || DECL_ARTIFICIAL (index))
 	    continue;
 	}
-      for (; field != index; field = DECL_CHAIN (field))
+      for (; field != index && TREE_TYPE (field) != anon_union_init_type;
+	   field = DECL_CHAIN (field))
 	{
 	  tree ftype;
 	  if (TREE_CODE (field) != FIELD_DECL