From: Jason Merrill <jason@redhat.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: gcc-patches@gcc.gnu.org, Marek Polacek <polacek@redhat.com>,
Jonathan Wakely <jwakely@redhat.com>
Subject: Re: [PATCH] c++, v2: Implement C++23 P2647R1 - Permitting static constexpr variables in constexpr functions
Date: Tue, 15 Nov 2022 18:36:38 -0500 [thread overview]
Message-ID: <c5025573-d5d6-1d6e-a629-a9624ea14d5c@redhat.com> (raw)
In-Reply-To: <Y3DYxNPWpM23FCtj@tucnak>
On 11/13/22 01:45, Jakub Jelinek wrote:
> On Fri, Nov 11, 2022 at 06:07:04PM +0100, Jakub Jelinek wrote:
>> The following patch on top of Marek's P2448 PR106649 patch
>> (mainly because that patch implements the previous __cpp_constexpr
>> feature test macro bump so this can't go in earlier; OT,
>> P2280R4 doesn't have any feature test macro?) implements this
>> simple paper.
>>
>> Ok for trunk if it passes bootstrap/regtest and is voted into C++23?
>
> Here is an updated patch that passed bootstrap/regtest, the only
> change is another testcase tweak.
>
> 2022-11-13 Jakub Jelinek <jakub@redhat.com>
>
> gcc/c-family/
> * c-cppbuiltin.cc (c_cpp_builtins): Bump __cpp_constexpr
> value from 202207L to 202211L.
> gcc/cp/
> * constexpr.cc (cxx_eval_constant_expression): Implement C++23
> P2647R1 - Permitting static constexpr variables in constexpr functions.
> Allow decl_maybe_constant_var_p static or thread_local vars for
> C++23.
This was accepted as a DR, so it shouldn't be limited to C++23 mode.
Certainly it should be allowed in C++20 mode; I don't have a strong
opinion about C++14/17. Jonathan, do you?
> (potential_constant_expression_1): Likewise.
> gcc/testsuite/
> * g++.dg/cpp23/constexpr-nonlit17.C: New test.
> * g++.dg/cpp23/feat-cxx2b.C: Adjust expected __cpp_constexpr
> value.
> * g++.dg/ext/stmtexpr19.C: Don't expect an error for C++23 or later.
>
> --- gcc/c-family/c-cppbuiltin.cc.jj 2022-11-11 17:14:52.021613271 +0100
> +++ gcc/c-family/c-cppbuiltin.cc 2022-11-11 17:17:45.065265246 +0100
> @@ -1074,7 +1074,7 @@ c_cpp_builtins (cpp_reader *pfile)
> /* Set feature test macros for C++23. */
> cpp_define (pfile, "__cpp_size_t_suffix=202011L");
> cpp_define (pfile, "__cpp_if_consteval=202106L");
> - cpp_define (pfile, "__cpp_constexpr=202207L");
> + cpp_define (pfile, "__cpp_constexpr=202211L");
> cpp_define (pfile, "__cpp_multidimensional_subscript=202110L");
> cpp_define (pfile, "__cpp_named_character_escapes=202207L");
> cpp_define (pfile, "__cpp_static_call_operator=202207L");
> --- gcc/cp/constexpr.cc.jj 2022-11-11 17:14:52.024613231 +0100
> +++ gcc/cp/constexpr.cc 2022-11-11 17:16:54.384952917 +0100
> @@ -7085,7 +7085,8 @@ cxx_eval_constant_expression (const cons
> && (TREE_STATIC (r)
> || (CP_DECL_THREAD_LOCAL_P (r) && !DECL_REALLY_EXTERN (r)))
> /* Allow __FUNCTION__ etc. */
> - && !DECL_ARTIFICIAL (r))
> + && !DECL_ARTIFICIAL (r)
> + && (cxx_dialect < cxx23 || !decl_maybe_constant_var_p (r)))
> {
> if (!ctx->quiet)
> {
> @@ -9577,7 +9578,10 @@ potential_constant_expression_1 (tree t,
> tmp = DECL_EXPR_DECL (t);
> if (VAR_P (tmp) && !DECL_ARTIFICIAL (tmp))
> {
> - if (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp))
> + if (CP_DECL_THREAD_LOCAL_P (tmp)
> + && !DECL_REALLY_EXTERN (tmp)
> + && (cxx_dialect < cxx23
> + || !decl_maybe_constant_var_p (tmp)))
> {
> if (flags & tf_error)
> constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> @@ -9585,7 +9589,9 @@ potential_constant_expression_1 (tree t,
> "%<constexpr%> context", tmp);
> return false;
> }
> - else if (TREE_STATIC (tmp))
> + else if (TREE_STATIC (tmp)
> + && (cxx_dialect < cxx23
> + || !decl_maybe_constant_var_p (tmp)))
> {
> if (flags & tf_error)
> constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> --- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C.jj 2022-11-11 17:59:59.972852793 +0100
> +++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C 2022-11-11 17:59:38.725141231 +0100
> @@ -0,0 +1,12 @@
> +// P2647R1 - Permitting static constexpr variables in constexpr functions
> +// { dg-do compile { target c++23 } }
> +
> +constexpr char
> +test ()
> +{
> + static const int x = 5;
> + static constexpr char c[] = "Hello World";
> + return *(c + x);
> +}
> +
> +static_assert (test () == ' ');
> --- gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C.jj 2022-11-11 17:14:52.194610922 +0100
> +++ gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C 2022-11-11 17:48:56.038865825 +0100
> @@ -134,8 +134,8 @@
>
> #ifndef __cpp_constexpr
> # error "__cpp_constexpr"
> -#elif __cpp_constexpr != 202207
> -# error "__cpp_constexpr != 202207"
> +#elif __cpp_constexpr != 202211
> +# error "__cpp_constexpr != 202211"
> #endif
>
> #ifndef __cpp_decltype_auto
> --- gcc/testsuite/g++.dg/ext/stmtexpr19.C.jj 2020-01-14 20:02:46.839608995 +0100
> +++ gcc/testsuite/g++.dg/ext/stmtexpr19.C 2022-11-12 09:17:40.706245495 +0100
> @@ -8,7 +8,7 @@ const test* setup()
> {
> static constexpr test atest =
> {
> - ({ static const int inner = 123; &inner; }) // { dg-error "static" }
> + ({ static const int inner = 123; &inner; }) // { dg-error "static" "" { target c++20_down } }
> };
>
> return &atest;
>
>
> Jakub
>
next prev parent reply other threads:[~2022-11-15 23:36 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-11 17:07 [PATCH] c++: " Jakub Jelinek
2022-11-13 11:45 ` [PATCH] c++, v2: " Jakub Jelinek
2022-11-15 23:36 ` Jason Merrill [this message]
2022-11-15 23:50 ` Jakub Jelinek
2022-11-16 0:27 ` Jonathan Wakely
2022-11-16 6:19 ` Jakub Jelinek
2022-11-16 13:20 ` Jason Merrill
2022-11-16 14:08 ` Jakub Jelinek
2022-11-16 14:33 ` Jason Merrill
2022-11-16 14:46 ` Jakub Jelinek
2022-11-16 20:26 ` Jason Merrill
2022-11-17 9:13 ` [PATCH] c++, v3: " Jakub Jelinek
2022-11-17 14:42 ` Jason Merrill
2022-11-17 18:42 ` Jakub Jelinek
2022-11-17 20:42 ` [PATCH] c++, v4: " Jakub Jelinek
2022-11-18 0:15 ` Marek Polacek
2022-11-18 7:48 ` Jakub Jelinek
2022-11-18 15:03 ` Marek Polacek
2022-11-18 15:14 ` Jakub Jelinek
2022-11-18 16:24 ` Jason Merrill
2022-11-18 16:34 ` Jakub Jelinek
2022-11-18 16:52 ` Jason Merrill
2022-11-18 0:28 ` Jason Merrill
2022-11-18 9:10 ` [PATCH] c++, v5: " Jakub Jelinek
2022-11-16 0:26 ` [PATCH] c++, v2: " Jonathan Wakely
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