re PR c++/48035 (Mismatch on size of class when initializing hierarchy involving virtual inheritance and empty base classes)

	PR c++/48035
	* init.c (build_zero_init_1): Extracted from build_zero_init.
	Add FIELD_SIZE argument, if non-NULL and field bit_position
	as not smaller than that, don't add that field's initializer.
	Pass DECL_SIZE as last argument to build_zero_init_1
	for DECL_FIELD_IS_BASE fields.
	(build_zero_init): Use build_zero_init_1.

	* g++.dg/inherit/virtual8.C: New test.

From-SVN: r170874

1 files changed, 49 insertions, 11 deletions

diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 56f66fa..e1961c8 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -1,7 +1,7 @@
 /* Handle initialization things in C++.
    Copyright (C) 1987, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
-   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
-   Free Software Foundation, Inc.
+   1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
+   2011 Free Software Foundation, Inc.
    Contributed by Michael Tiemann (tiemann@cygnus.com)
 
 This file is part of GCC.
@@ -140,10 +140,13 @@ initialize_vtbl_ptrs (tree addr)
    is the number of elements in the array.  If STATIC_STORAGE_P is
    TRUE, initializers are only generated for entities for which
    zero-initialization does not simply mean filling the storage with
-   zero bytes.  */
+   zero bytes.  FIELD_SIZE, if non-NULL, is the bit size of the field,
+   subfields with bit positions at or above that bit size shouldn't
+   be added.  */
 
-tree
-build_zero_init (tree type, tree nelts, bool static_storage_p)
+static tree
+build_zero_init_1 (tree type, tree nelts, bool static_storage_p,
+		   tree field_size)
 {
   tree init = NULL_TREE;
 
@@ -188,15 +191,32 @@ build_zero_init (tree type, tree nelts, bool static_storage_p)
 	  if (TREE_CODE (field) != FIELD_DECL)
 	    continue;
 
+	  /* Don't add virtual bases for base classes if they are beyond
+	     the size of the current field, that means it is present
+	     somewhere else in the object.  */
+	  if (field_size)
+	    {
+	      tree bitpos = bit_position (field);
+	      if (TREE_CODE (bitpos) == INTEGER_CST
+		  && !tree_int_cst_lt (bitpos, field_size))
+		continue;
+	    }
+
 	  /* Note that for class types there will be FIELD_DECLs
 	     corresponding to base classes as well.  Thus, iterating
 	     over TYPE_FIELDs will result in correct initialization of
 	     all of the subobjects.  */
 	  if (!static_storage_p || !zero_init_p (TREE_TYPE (field)))
 	    {
-	      tree value = build_zero_init (TREE_TYPE (field),
-					    /*nelts=*/NULL_TREE,
-					    static_storage_p);
+	      tree new_field_size
+		= (DECL_FIELD_IS_BASE (field)
+		   && DECL_SIZE (field)
+		   && TREE_CODE (DECL_SIZE (field)) == INTEGER_CST)
+		  ? DECL_SIZE (field) : NULL_TREE;
+	      tree value = build_zero_init_1 (TREE_TYPE (field),
+					      /*nelts=*/NULL_TREE,
+					      static_storage_p,
+					      new_field_size);
 	      if (value)
 		CONSTRUCTOR_APPEND_ELT(v, field, value);
 	    }
@@ -244,9 +264,9 @@ build_zero_init (tree type, tree nelts, bool static_storage_p)
 	    ce->index = build2 (RANGE_EXPR, sizetype, size_zero_node,
 				max_index);
 
-	  ce->value = build_zero_init (TREE_TYPE (type),
-				       /*nelts=*/NULL_TREE,
-				       static_storage_p);
+	  ce->value = build_zero_init_1 (TREE_TYPE (type),
+					 /*nelts=*/NULL_TREE,
+					 static_storage_p, NULL_TREE);
 	}
 
       /* Build a constructor to contain the initializations.  */
@@ -264,6 +284,24 @@ build_zero_init (tree type, tree nelts, bool static_storage_p)
   return init;
 }
 
+/* Return an expression for the zero-initialization of an object with
+   type T.  This expression will either be a constant (in the case
+   that T is a scalar), or a CONSTRUCTOR (in the case that T is an
+   aggregate), or NULL (in the case that T does not require
+   initialization).  In either case, the value can be used as
+   DECL_INITIAL for a decl of the indicated TYPE; it is a valid static
+   initializer. If NELTS is non-NULL, and TYPE is an ARRAY_TYPE, NELTS
+   is the number of elements in the array.  If STATIC_STORAGE_P is
+   TRUE, initializers are only generated for entities for which
+   zero-initialization does not simply mean filling the storage with
+   zero bytes.  */
+
+tree
+build_zero_init (tree type, tree nelts, bool static_storage_p)
+{
+  return build_zero_init_1 (type, nelts, static_storage_p, NULL_TREE);
+}
+
 /* Return a suitable initializer for value-initializing an object of type
    TYPE, as described in [dcl.init].  */