class.c (create_vtable_ptr): Put the vtable at the beginning of the class, not…

class.c (create_vtable_ptr): Put the vtable at the beginning of the class, not the end, in the new ABI.

	* class.c (create_vtable_ptr): Put the vtable at the beginning of
	the class, not the end, in the new ABI.
	* tree.c (propagate_binfo_offsets): Do the right thing for the new
	ABI.

From-SVN: r31120

gcc/cp/ChangeLog

 1999-12-29  Mark Mitchell  <mark@codesourcery.com>
 
+	* class.c (create_vtable_ptr): Put the vtable at the beginning of
+	the class, not the end, in the new ABI.
+	* tree.c (propagate_binfo_offsets): Do the right thing for the new
+	ABI.
+
+1999-12-29  Mark Mitchell  <mark@codesourcery.com>
+
 	* cp-tree.h (lang_type): Add nearly_empty_p.  Adjust dummy.
 	(CLASSTYPE_NEARLY_EMPTY_P): New macro.
 	* class.c (check_bases): Update CLASSTYPE_NEARLY_EMPTY_P.

gcc/cp/class.c

@@ -4136,7 +4136,22 @@ create_vtable_ptr (t, empty_p, has_virtual_p, max_has_virtual_p,
 				     empty_p);
 
       /* Add the new field to the list of fields in this class.  */
-      TYPE_FIELDS (t) = chainon (TYPE_FIELDS (t), TYPE_VFIELD (t));
+      if (!flag_new_abi)
+	/* In the old ABI, the vtable pointer goes at the end of the
+	   class.  */
+	TYPE_FIELDS (t) = chainon (TYPE_FIELDS (t), TYPE_VFIELD (t));
+      else
+	{
+	  /* But in the new ABI, the vtable pointer is the first thing
+	     in the class.  */
+	  TYPE_FIELDS (t) = chainon (TYPE_VFIELD (t), TYPE_FIELDS (t));
+	  /* If there were any baseclasses, they can't possibly be at
+	     offset zero any more, because that's where the vtable
+	     pointer is.  So, converting to a base class is going to
+	     take work.  */
+	  if (CLASSTYPE_N_BASECLASSES (t))
+	    TYPE_BASE_CONVS_MAY_REQUIRE_CODE_P (t) = 1;
+	}
 
       /* We can't yet add this new field to the list of all virtual
 	 function table pointers in this class.  The

gcc/cp/tree.c

@@ -671,36 +671,81 @@ propagate_binfo_offsets (binfo, offset)
   tree binfos = BINFO_BASETYPES (binfo);
   int i, n_baselinks = binfos ? TREE_VEC_LENGTH (binfos) : 0;
 
-  for (i = 0; i < n_baselinks; /* note increment is done in the loop.  */)
+  if (flag_new_abi)
     {
-      tree base_binfo = TREE_VEC_ELT (binfos, i);
-
-      if (TREE_VIA_VIRTUAL (base_binfo))
-	i += 1;
-      else
+      for (i = 0; i < n_baselinks; ++i)
 	{
-	  int j;
-	  tree delta = NULL_TREE;
-
-	  for (j = i+1; j < n_baselinks; j++)
-	    if (! TREE_VIA_VIRTUAL (TREE_VEC_ELT (binfos, j)))
-	      {
-		/* The next basetype offset must take into account the space
-		   between the classes, not just the size of each class.  */
-		delta = size_binop (MINUS_EXPR,
-				    BINFO_OFFSET (TREE_VEC_ELT (binfos, j)),
-				    BINFO_OFFSET (base_binfo));
-		break;
-	      }
-
-	  BINFO_OFFSET (base_binfo) = offset;
+	  tree base_binfo;
+
+	  /* Figure out which base we're looking at.  */
+	  base_binfo = TREE_VEC_ELT (binfos, i);
+
+	  /* Skip virtual bases.  Their BINFO_OFFSET doesn't matter
+	     since they are always reached by using offsets looked up
+	     at run-time.  */
+	  if (TREE_VIA_VIRTUAL (base_binfo))
+	    continue;
+
+	  /* Whatever offset this class used to have in its immediate
+	     derived class, it is now at OFFSET more bytes in its
+	     final derived class, since the immediate derived class is
+	     already at the indicated OFFSET.  */
+	  BINFO_OFFSET (base_binfo)
+	    = size_binop (PLUS_EXPR, BINFO_OFFSET (base_binfo), offset);
 
 	  propagate_binfo_offsets (base_binfo, offset);
+	}
+    }
+  else
+    {
+      /* This algorithm, used for the old ABI, is neither simple, nor
+	 general.  For example, it mishandles the case of:
+       
+           struct A;
+	   struct B : public A;
+	   struct C : public B;
+	   
+	 if B is at offset zero in C, but A is not in offset zero in
+	 B.  In that case, it sets the BINFO_OFFSET for A to zero.
+	 (This sitution arises in the new ABI if B has virtual
+	 functions, but A does not.)  Rather than change this
+	 algorithm, and risking breaking the old ABI, it is preserved
+	 here.  */
+      for (i = 0; i < n_baselinks; /* note increment is done in the
+				      loop.  */)
+	{
+	  tree base_binfo = TREE_VEC_ELT (binfos, i);
 
-	  /* Go to our next class that counts for offset propagation.  */
-	  i = j;
-	  if (i < n_baselinks)
-	    offset = size_binop (PLUS_EXPR, offset, delta);
+	  if (TREE_VIA_VIRTUAL (base_binfo))
+	    i += 1;
+	  else
+	    {
+	      int j;
+	      tree delta = NULL_TREE;
+
+	      for (j = i+1; j < n_baselinks; j++)
+		if (! TREE_VIA_VIRTUAL (TREE_VEC_ELT (binfos, j)))
+		  {
+		    /* The next basetype offset must take into account
+		       the space between the classes, not just the
+		       size of each class.  */
+		    delta = size_binop (MINUS_EXPR,
+					BINFO_OFFSET (TREE_VEC_ELT (binfos, 
+								    j)),
+					BINFO_OFFSET (base_binfo));
+		    break;
+		  }
+
+	      BINFO_OFFSET (base_binfo) = offset;
+
+	      propagate_binfo_offsets (base_binfo, offset);
+
+	      /* Go to our next class that counts for offset
+                 propagation.  */
+	      i = j;
+	      if (i < n_baselinks)
+		offset = size_binop (PLUS_EXPR, offset, delta);
+	    }
 	}
     }
 }