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Re: [C++ PATCH] Fix up bitfield handling in typeid (PR c++/87547)
- From: Jason Merrill <jason at redhat dot com>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: gcc-patches List <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 10 Oct 2018 20:18:27 -0400
- Subject: Re: [C++ PATCH] Fix up bitfield handling in typeid (PR c++/87547)
- References: <20181010091731.GT11625@tucnak>
OK.
On Wed, Oct 10, 2018 at 5:17 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> Hi!
>
> typeid of an expression that is a bitfield right now returns various weird
> results, depending on what exact type ignoring precision we choose for the
> bitfield. Haven't found exact wording in the standard that would back this
> out though. clang++ agrees with the patched g++ though.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> 2018-10-10 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/87547
> * rtti.c (get_tinfo_decl_dynamic): Use unlowered_expr_type instead
> of TREE_TYPE.
>
> * g++.dg/rtti/typeid12.C: New test.
>
> --- gcc/cp/rtti.c.jj 2018-08-27 17:50:43.782489578 +0200
> +++ gcc/cp/rtti.c 2018-10-09 10:52:42.348604424 +0200
> @@ -273,7 +273,7 @@ get_tinfo_decl_dynamic (tree exp, tsubst
> exp = resolve_nondeduced_context (exp, complain);
>
> /* peel back references, so they match. */
> - type = non_reference (TREE_TYPE (exp));
> + type = non_reference (unlowered_expr_type (exp));
>
> /* Peel off cv qualifiers. */
> type = TYPE_MAIN_VARIANT (type);
> --- gcc/testsuite/g++.dg/rtti/typeid12.C.jj 2018-10-09 10:42:19.580094220 +0200
> +++ gcc/testsuite/g++.dg/rtti/typeid12.C 2018-10-09 10:42:04.105354872 +0200
> @@ -0,0 +1,16 @@
> +// PR c++/87547
> +// { dg-do run }
> +
> +#include <typeinfo>
> +
> +struct S { unsigned int a : 4; unsigned int b : 12; int c; unsigned long d : 8; } s;
> +
> +int
> +main ()
> +{
> + if (typeid (s.a) != typeid (unsigned int)
> + || typeid (s.b) != typeid (unsigned int)
> + || typeid (s.c) != typeid (int)
> + || typeid (s.d) != typeid (unsigned long))
> + __builtin_abort ();
> +}
>
> Jakub