We have a special 'as-base' instance of each class, for use in derived
layouts. for some classes this is just the regular class itself, but
for others it's a new instance. This instance is not in the
class-members, and that's now biting me on the modules branch (i'd been
punting on it before).
This patch does a few cleanup, which make sense on trunk.
We do seem to be creating this instance in more cases than necessary --
looking at (CLASSTYPE_NON_LAYOUT_POD_P (t) || CLASSTYPE_EMPTY_P (t)).
The former claims to 'not be the language non-pod'. but it actually is
if you're in c++98-land. I /think/ we only need a special instance for
a) empty classes
b) classes with virtual bases
c) non-pod classes with tail padding (which could be overlaid in
derivation).
But that's a cleanup for another day.
nathan
--
Nathan Sidwell
2017-10-20 Nathan Sidwell <nat...@acm.org>
* class.c (layout_class_type): Cleanup as-base creation, determine
mode here.
(finish_struct_1): ... not here.
Index: class.c
===================================================================
--- class.c (revision 253948)
+++ class.c (working copy)
@@ -5992,8 +5992,6 @@ layout_class_type (tree t, tree *virtual
bool last_field_was_bitfield = false;
/* The location at which the next field should be inserted. */
tree *next_field;
- /* T, as a base class. */
- tree base_t;
/* Keep track of the first non-static data member. */
non_static_data_members = TYPE_FIELDS (t);
@@ -6218,15 +6216,11 @@ layout_class_type (tree t, tree *virtual
that the type is laid out they are no longer important. */
remove_zero_width_bit_fields (t);
- /* Create the version of T used for virtual bases. We do not use
- make_class_type for this version; this is an artificial type. For
- a POD type, we just reuse T. */
if (CLASSTYPE_NON_LAYOUT_POD_P (t) || CLASSTYPE_EMPTY_P (t))
{
- base_t = make_node (TREE_CODE (t));
-
- /* Set the size and alignment for the new type. */
- tree eoc;
+ /* T needs a different layout as a base (eliding virtual bases
+ or whatever). Create that version. */
+ tree base_t = make_node (TREE_CODE (t));
/* If the ABI version is not at least two, and the last
field was a bit-field, RLI may not be on a byte
@@ -6235,7 +6229,7 @@ layout_class_type (tree t, tree *virtual
indicates the total number of bits used. Therefore,
rli_size_so_far, rather than rli_size_unit_so_far, is
used to compute TYPE_SIZE_UNIT. */
- eoc = end_of_class (t, /*include_virtuals_p=*/0);
+ tree eoc = end_of_class (t, /*include_virtuals_p=*/0);
TYPE_SIZE_UNIT (base_t)
= size_binop (MAX_EXPR,
fold_convert (sizetype,
@@ -6252,7 +6246,8 @@ layout_class_type (tree t, tree *virtual
SET_TYPE_ALIGN (base_t, rli->record_align);
TYPE_USER_ALIGN (base_t) = TYPE_USER_ALIGN (t);
- /* Copy the fields from T. */
+ /* Copy the non-static data members of T. This will include its
+ direct non-virtual bases & vtable. */
next_field = &TYPE_FIELDS (base_t);
for (field = TYPE_FIELDS (t); field; field = DECL_CHAIN (field))
if (TREE_CODE (field) == FIELD_DECL)
@@ -6263,9 +6258,14 @@ layout_class_type (tree t, tree *virtual
}
*next_field = NULL_TREE;
+ /* We use the base type for trivial assignments, and hence it
+ needs a mode. */
+ compute_record_mode (base_t);
+
+ TYPE_CONTEXT (base_t) = t;
+
/* Record the base version of the type. */
CLASSTYPE_AS_BASE (t) = base_t;
- TYPE_CONTEXT (base_t) = t;
}
else
CLASSTYPE_AS_BASE (t) = t;
@@ -6822,11 +6822,6 @@ finish_struct_1 (tree t)
set_class_bindings (t);
- if (CLASSTYPE_AS_BASE (t) != t)
- /* We use the base type for trivial assignments, and hence it
- needs a mode. */
- compute_record_mode (CLASSTYPE_AS_BASE (t));
-
/* With the layout complete, check for flexible array members and
zero-length arrays that might overlap other members in the final
layout. */
