Re: C++ PATCH for c++/65556 (ICE with switch and bit-fields)

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Fri, Mar 27, 2015 at 7:38 AM, Marek Polacek <polacek@redhat.com> wrote:
> In this testcase we were crashing while trying to gimplify a switch, because
> the types of the switch condition and case constants didn't match.  This ICE
> started with my -Wswitch-with-enum-bit-fields fix where I used the unlowered
> type so that we're able to get hold of the enum type.  The problem with that
> is with ordinary bit-fields: we'll get the underlying type (e.g. long int),
> but subsequent perform_integral_promotions promotes that to int, see
> cp_perform_integral_promotions.  Fixed by using the type of the condition in
> case we're not dealing with an enum bit-field, i.e. do what we've been doing
> before the -Wswitch fix, which ought to make this fix very safe.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2015-03-27  Marek Polacek  <polacek@redhat.com>
>
>         PR c++/65556
>         * semantics.c (finish_switch_cond): If the unlowered type is not an
>         enum, use the type of the condition.
>
>         * c-c++-common/pr65556.c: New test.
>
> diff --git gcc/cp/semantics.c gcc/cp/semantics.c
> index f325e41..74af7e8 100644
> --- gcc/cp/semantics.c
> +++ gcc/cp/semantics.c
> @@ -1165,6 +1165,8 @@ finish_switch_cond (tree cond, tree switch_stmt)
>         }
>        /* We want unlowered type here to handle enum bit-fields.  */
>        orig_type = unlowered_expr_type (cond);
> +      if (TREE_CODE (orig_type) != ENUMERAL_TYPE)
> +       orig_type = TREE_TYPE (cond);
>        if (cond != error_mark_node)
>         {
>           /* Warn if the condition has boolean value.  */
> diff --git gcc/testsuite/c-c++-common/pr65556.c gcc/testsuite/c-c++-common/pr65556.c
> index e69de29..c6729a1 100644
> --- gcc/testsuite/c-c++-common/pr65556.c
> +++ gcc/testsuite/c-c++-common/pr65556.c
> @@ -0,0 +1,23 @@
> +/* PR c++/65556 */
> +/* { dg-do compile } */
> +
> +struct S
> +{
> +  long l: 1;
> +  long l2: 41;
> +  unsigned long ul: 1;
> +  unsigned long ul2: 41;
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This won't work with 32-bit long.

-- 
H.J.