On Wed, Aug 29, 2018 at 01:36:15PM -0400, Nathan Sidwell wrote:
> --- gcc/cp/class.c (revision 263959)
> +++ gcc/cp/class.c (working copy)
> @@ -4041,6 +4041,32 @@ layout_nonempty_base_or_field (record_la
> field_p = true;
> }
>
> + /* PR c++/87137 When ms_bitfield_layout_p is in effect, place_field
> + used to just look at the DECL's TREE_CHAIN to see if it ended the
> + struct. That was ok when only FIELD_DECLs and TYPE_DECLs were on
> + the chain, AND the TYPE_DECLs were known to be last. That
> + stopped working when other things, such as static members were
> + also placed there. However, in GCC 8 onwards all members are on
> + the chain (adding member functions). We want to restore the
> + pre-GCC-8 behaviour, so the ABI doesn't change in a point
> + release. Because the middle-end doesn't know about
> + TEMPLATE_DECL, we have to do nastiness here, to make DECL_CHAIN
> + look like it used to before calling place_field. THIS IS STILL
> + WRONG, but it's the same wrongness ass gcc-7 and earier. */
s/ass gcc-7 and earier/as gcc-7 and earlier/ ?
> + tree chain = NULL_TREE;
> + if (targetm.ms_bitfield_layout_p (rli->t))
> + {
> + tree probe = decl;
> + while ((probe = TREE_CHAIN (probe)))
Any reason you are using TREE_CHAIN rather than DECL_CHAIN everywhere (in
comments as well as here and below?
Shouldn't all chain elts be decls?
> + if (TREE_CODE (STRIP_TEMPLATE (probe)) != FUNCTION_DECL)
> + break;
> + if (probe != TREE_CHAIN (decl))
> + {
> + chain = TREE_CHAIN (decl);
> + TREE_CHAIN (decl) = probe;
> + }
> + }
> +
> /* Try to place the field. It may take more than one try if we have
> a hard time placing the field without putting two objects of the
> same type at the same address. */
> @@ -4111,6 +4137,11 @@ layout_nonempty_base_or_field (record_la
> break;
> }
>
> + if (chain)
> + /* Restore the original chain our ms-bifield-offset shenanigans
> + above overwrote. */
> + TREE_CHAIN (decl) = chain;
> +
> /* Now that we know where it will be placed, update its
> BINFO_OFFSET. */
> if (binfo && CLASS_TYPE_P (BINFO_TYPE (binfo)))
Jakub
