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Re: [C++ PATCH] Fix value initialized decltype(nullptr) in constexpr (PR c++/85553)
- 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: Fri, 27 Apr 2018 20:13:34 +0000
- Subject: Re: [C++ PATCH] Fix value initialized decltype(nullptr) in constexpr (PR c++/85553)
- References: <20180427180736.GY8577@tucnak>
Ok
On Fri, Apr 27, 2018, 2:07 PM Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
> init = fold (convert (type, nullptr_node)); unfortunately creates
> a NOP_EXPR around INTEGER_CST and constexpr.c doesn't consider that a valid
> constant; fold (convert (type, integer_zero_node)) we used previously
> on the other side emitted warnings.
>
> The following patch just builds the INTEGER_CST directly.
>
> Tested on x86_64-linux with make check-c++-all, ok for trunk and 8.1
> if it passes full bootstrap/regtest on {x86_64,i686}-linux?
>
> 2018-04-27 Jakub Jelinek <jakub@redhat.com>
>
> PR c++/85553
> * init.c (build_zero_init_1): For zero initialization of
> NULLPTR_TYPE_P type use build_int_cst directly.
>
> * g++.dg/cpp0x/Wzero-as-null-pointer-constant-3.C: Add dg-bogus
> directive.
> * g++.dg/cpp0x/constexpr-85553.C: New test.
>
> --- gcc/cp/init.c.jj 2018-04-27 19:11:56.613549524 +0200
> +++ gcc/cp/init.c 2018-04-27 19:20:50.102839130 +0200
> @@ -180,8 +180,10 @@ build_zero_init_1 (tree type, tree nelts
> items with static storage duration that are not otherwise
> initialized are initialized to zero. */
> ;
> - else if (TYPE_PTR_OR_PTRMEM_P (type) || NULLPTR_TYPE_P (type))
> + else if (TYPE_PTR_OR_PTRMEM_P (type))
> init = fold (convert (type, nullptr_node));
> + else if (NULLPTR_TYPE_P (type))
> + init = build_int_cst (type, 0);
> else if (SCALAR_TYPE_P (type))
> init = fold (convert (type, integer_zero_node));
> else if (RECORD_OR_UNION_CODE_P (TREE_CODE (type)))
> --- gcc/testsuite/g++.dg/cpp0x/Wzero-as-null-pointer-constant-3.C.jj
> 2018-04-12 10:22:56.640162364 +0200
> +++ gcc/testsuite/g++.dg/cpp0x/Wzero-as-null-pointer-constant-3.C
> 2018-04-27 19:23:58.349941329 +0200
> @@ -3,4 +3,4 @@
> // { dg-options "-Wzero-as-null-pointer-constant" }
>
> int* no_warn = {};
> -decltype( nullptr ) warn = {};
> +decltype( nullptr ) warn = {}; // { dg-bogus "zero as null pointer
> constant" }
> --- gcc/testsuite/g++.dg/cpp0x/constexpr-85553.C.jj 2018-04-27
> 19:24:33.547960437 +0200
> +++ gcc/testsuite/g++.dg/cpp0x/constexpr-85553.C 2018-04-27
> 19:24:51.456970160 +0200
> @@ -0,0 +1,4 @@
> +// PR c++/85553
> +// { dg-do compile { target c++11 } }
> +using T = decltype(nullptr);
> +const constexpr T foo{};
>
> Jakub
>