c++, v4: Implement C++23 P2647R1 - Permitting static constexpr variables in constexpr functions
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On Thu, Nov 17, 2022 at 07:42:40PM +0100, Jakub Jelinek via Gcc-patches wrote:
> I thought for older C++ this is to catch
> void
> foo ()
> {
> constexpr int a = ({ static constexpr int b = 2; b; });
> }
> and for C++23 the only 3 spots that diagnose those.
> But perhaps for C++20 or older we can check if the var has a context
> of a constexpr function (then assume cp_finish_decl errored or pedwarned
> already) and only error or pedwarn otherwise.
So, here is an updated patch, which in constexpr.cc will accept
DECL_EXPR of decl_*constant_var_p static/thread_local non-extern vars
for C++23 or if they are not declared in constexpr/consteval function.
So, the statement expression case will remain hard error for C++ <= 20 rather than
pedwarn, because due to the ctx->quiet vs. !ctx->quiet case I don't see
what else we could do, either something is a constant expression, or
it is not, but whether it is or is not shouldn't depend on
-Wpedantic/-Wno-pedantic/-Werror=pedantic.
2022-11-17 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_constant_var_p static or thread_local vars for
C++23 and later or if they are declared inside of constexpr or
consteval function.
(potential_constant_expression_1): Similarly, except use
decl_maybe_constant_var_p instead of decl_constant_var_p if
processing_template_decl.
* decl.cc (diagnose_static_in_constexpr): New function.
(start_decl): Remove diagnostics of static or thread_local
vars in constexpr or consteval functions.
(cp_finish_decl): Call diagnose_static_in_constexpr.
gcc/testsuite/
* g++.dg/cpp23/constexpr-nonlit17.C: New test.
* g++.dg/cpp23/constexpr-nonlit18.C: New test.
* g++.dg/cpp23/constexpr-nonlit19.C: New test.
* g++.dg/cpp23/constexpr-nonlit20.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++20 or later.
Jakub
Comments
On Thu, Nov 17, 2022 at 09:42:17PM +0100, Jakub Jelinek wrote:
> On Thu, Nov 17, 2022 at 07:42:40PM +0100, Jakub Jelinek via Gcc-patches wrote:
> > I thought for older C++ this is to catch
> > void
> > foo ()
> > {
> > constexpr int a = ({ static constexpr int b = 2; b; });
> > }
> > and for C++23 the only 3 spots that diagnose those.
> > But perhaps for C++20 or older we can check if the var has a context
> > of a constexpr function (then assume cp_finish_decl errored or pedwarned
> > already) and only error or pedwarn otherwise.
>
> So, here is an updated patch, which in constexpr.cc will accept
> DECL_EXPR of decl_*constant_var_p static/thread_local non-extern vars
> for C++23 or if they are not declared in constexpr/consteval function.
> So, the statement expression case will remain hard error for C++ <= 20 rather than
> pedwarn, because due to the ctx->quiet vs. !ctx->quiet case I don't see
> what else we could do, either something is a constant expression, or
> it is not, but whether it is or is not shouldn't depend on
> -Wpedantic/-Wno-pedantic/-Werror=pedantic.
>
> 2022-11-17 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_constant_var_p static or thread_local vars for
> C++23 and later or if they are declared inside of constexpr or
> consteval function.
> (potential_constant_expression_1): Similarly, except use
> decl_maybe_constant_var_p instead of decl_constant_var_p if
> processing_template_decl.
> * decl.cc (diagnose_static_in_constexpr): New function.
> (start_decl): Remove diagnostics of static or thread_local
> vars in constexpr or consteval functions.
> (cp_finish_decl): Call diagnose_static_in_constexpr.
> gcc/testsuite/
> * g++.dg/cpp23/constexpr-nonlit17.C: New test.
> * g++.dg/cpp23/constexpr-nonlit18.C: New test.
> * g++.dg/cpp23/constexpr-nonlit19.C: New test.
> * g++.dg/cpp23/constexpr-nonlit20.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++20 or later.
>
> --- gcc/c-family/c-cppbuiltin.cc.jj 2022-11-17 09:00:42.106249011 +0100
> +++ gcc/c-family/c-cppbuiltin.cc 2022-11-17 09:01:49.286320527 +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=202211L");
> cpp_define (pfile, "__cpp_named_character_escapes=202207L");
> cpp_define (pfile, "__cpp_static_call_operator=202207L");
> --- gcc/cp/constexpr.cc.jj 2022-11-17 08:48:30.530357181 +0100
> +++ gcc/cp/constexpr.cc 2022-11-17 20:53:15.432408015 +0100
> @@ -7100,17 +7100,35 @@ cxx_eval_constant_expression (const cons
> /* Allow __FUNCTION__ etc. */
> && !DECL_ARTIFICIAL (r))
> {
> - if (!ctx->quiet)
> + bool ok = decl_constant_var_p (r);
> + /* Since P2647R1 control can pass through definitions of static
> + or thread_local vars usable in constant expressions.
> + In C++20 or older, if such vars are declared inside of
> + constexpr or consteval function, diagnose_static_in_constexpr
> + should have already pedwarned on those. Otherwise they could
> + be e.g. in a statement expression, reject those before
> + C++23. */
> + if (ok && cxx_dialect < cxx23)
> {
> - if (CP_DECL_THREAD_LOCAL_P (r))
> - error_at (loc, "control passes through definition of %qD "
> - "with thread storage duration", r);
> - else
> - error_at (loc, "control passes through definition of %qD "
> - "with static storage duration", r);
> + tree fnctx = decl_function_context (r);
> + if (fnctx == NULL_TREE
> + || !DECL_DECLARED_CONSTEXPR_P (fnctx))
> + ok = false;
FWIW, I couldn't find a way to trigger this code.
> + }
> + if (!ok)
> + {
> + if (!ctx->quiet)
> + {
> + if (CP_DECL_THREAD_LOCAL_P (r))
> + error_at (loc, "control passes through definition of "
> + "%qD with thread storage duration", r);
> + else
> + error_at (loc, "control passes through definition of "
> + "%qD with static storage duration", r);
> + }
> + *non_constant_p = true;
> + break;
> }
> - *non_constant_p = true;
> - break;
> }
>
> if (AGGREGATE_TYPE_P (TREE_TYPE (r))
> @@ -9588,21 +9606,41 @@ 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 (flags & tf_error)
> - constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> - "%qD defined %<thread_local%> in "
> - "%<constexpr%> context", tmp);
> - return false;
> - }
> - else if (TREE_STATIC (tmp))
> + if (TREE_STATIC (tmp)
> + || (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp)))
> {
> - if (flags & tf_error)
> - constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> - "%qD defined %<static%> in %<constexpr%> "
> - "context", tmp);
> - return false;
> + bool ok = (processing_template_decl
> + ? decl_maybe_constant_var_p (tmp)
> + : decl_constant_var_p (tmp));
> + /* Since P2647R1 control can pass through definitions of static
> + or thread_local vars usable in constant expressions.
> + In C++20 or older, if such vars are declared inside of
> + constexpr or consteval function, diagnose_static_in_constexpr
> + should have already pedwarned on those. Otherwise they could
> + be e.g. in a statement expression, reject those before
> + C++23. */
> + if (ok && cxx_dialect < cxx23)
> + {
> + tree fnctx = decl_function_context (tmp);
> + if (fnctx == NULL_TREE
> + || !DECL_DECLARED_CONSTEXPR_P (fnctx))
> + ok = false;
> + }
> + if (!ok)
> + {
> + if (flags & tf_error)
> + {
> + if (CP_DECL_THREAD_LOCAL_P (tmp))
> + constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> + "%qD defined %<thread_local%> in "
> + "%<constexpr%> context", tmp);
> + else
> + constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> + "%qD defined %<static%> in "
> + "%<constexpr%> context", tmp);
> + }
> + return false;
> + }
> }
> else if (!check_for_uninitialized_const_var
> (tmp, /*constexpr_context_p=*/true, flags))
> --- gcc/cp/decl.cc.jj 2022-11-16 14:44:43.692339668 +0100
> +++ gcc/cp/decl.cc 2022-11-17 20:53:44.102011594 +0100
> @@ -5600,6 +5600,57 @@ groktypename (cp_decl_specifier_seq *typ
> return type;
> }
>
> +/* For C++17 and older diagnose static or thread_local decls in constexpr
> + or consteval functions. For C++20 similarly, except if they are
In C++17 we don't support consteval so I guess drop the "or consteval "?
BTW, I notice that the patch breaks
g++.dg/cpp1y/lambda-generic-func1.C
g++.dg/cpp1z/constexpr-lambda16.C
Maybe they just need dg- tweaks.
Marek
On 11/17/22 15:42, Jakub Jelinek wrote:
> On Thu, Nov 17, 2022 at 07:42:40PM +0100, Jakub Jelinek via Gcc-patches wrote:
>> I thought for older C++ this is to catch
>> void
>> foo ()
>> {
>> constexpr int a = ({ static constexpr int b = 2; b; });
>> }
>> and for C++23 the only 3 spots that diagnose those.
>> But perhaps for C++20 or older we can check if the var has a context
>> of a constexpr function (then assume cp_finish_decl errored or pedwarned
>> already) and only error or pedwarn otherwise.
We could, but I wouldn't bother to enforce this specially for
statement-expressions, which are already an extension.
OTOH, we should test that static constexpr is handled properly for
lambdas, i.e. this should still fail:
constexpr int q = [](int i)
{ static constexpr int x = 42; return x+i; }(24);
> So, here is an updated patch, which in constexpr.cc will accept
> DECL_EXPR of decl_*constant_var_p static/thread_local non-extern vars
> for C++23 or if they are not declared in constexpr/consteval function.
> So, the statement expression case will remain hard error for C++ <= 20 rather than
> pedwarn, because due to the ctx->quiet vs. !ctx->quiet case I don't see
> what else we could do, either something is a constant expression, or
> it is not, but whether it is or is not shouldn't depend on
> -Wpedantic/-Wno-pedantic/-Werror=pedantic.
>
> 2022-11-17 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_constant_var_p static or thread_local vars for
> C++23 and later or if they are declared inside of constexpr or
> consteval function.
> (potential_constant_expression_1): Similarly, except use
> decl_maybe_constant_var_p instead of decl_constant_var_p if
> processing_template_decl.
> * decl.cc (diagnose_static_in_constexpr): New function.
> (start_decl): Remove diagnostics of static or thread_local
> vars in constexpr or consteval functions.
> (cp_finish_decl): Call diagnose_static_in_constexpr.
> gcc/testsuite/
> * g++.dg/cpp23/constexpr-nonlit17.C: New test.
> * g++.dg/cpp23/constexpr-nonlit18.C: New test.
> * g++.dg/cpp23/constexpr-nonlit19.C: New test.
> * g++.dg/cpp23/constexpr-nonlit20.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++20 or later.
>
> --- gcc/c-family/c-cppbuiltin.cc.jj 2022-11-17 09:00:42.106249011 +0100
> +++ gcc/c-family/c-cppbuiltin.cc 2022-11-17 09:01:49.286320527 +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=202211L");
> cpp_define (pfile, "__cpp_named_character_escapes=202207L");
> cpp_define (pfile, "__cpp_static_call_operator=202207L");
> --- gcc/cp/constexpr.cc.jj 2022-11-17 08:48:30.530357181 +0100
> +++ gcc/cp/constexpr.cc 2022-11-17 20:53:15.432408015 +0100
> @@ -7100,17 +7100,35 @@ cxx_eval_constant_expression (const cons
> /* Allow __FUNCTION__ etc. */
> && !DECL_ARTIFICIAL (r))
> {
> - if (!ctx->quiet)
> + bool ok = decl_constant_var_p (r);
> + /* Since P2647R1 control can pass through definitions of static
> + or thread_local vars usable in constant expressions.
> + In C++20 or older, if such vars are declared inside of
> + constexpr or consteval function, diagnose_static_in_constexpr
> + should have already pedwarned on those. Otherwise they could
> + be e.g. in a statement expression, reject those before
> + C++23. */
> + if (ok && cxx_dialect < cxx23)
> {
> - if (CP_DECL_THREAD_LOCAL_P (r))
> - error_at (loc, "control passes through definition of %qD "
> - "with thread storage duration", r);
> - else
> - error_at (loc, "control passes through definition of %qD "
> - "with static storage duration", r);
> + tree fnctx = decl_function_context (r);
> + if (fnctx == NULL_TREE
> + || !DECL_DECLARED_CONSTEXPR_P (fnctx))
> + ok = false;
> + }
> + if (!ok)
> + {
> + if (!ctx->quiet)
> + {
> + if (CP_DECL_THREAD_LOCAL_P (r))
> + error_at (loc, "control passes through definition of "
> + "%qD with thread storage duration", r);
> + else
> + error_at (loc, "control passes through definition of "
> + "%qD with static storage duration", r);
> + }
> + *non_constant_p = true;
> + break;
> }
> - *non_constant_p = true;
> - break;
> }
>
> if (AGGREGATE_TYPE_P (TREE_TYPE (r))
> @@ -9588,21 +9606,41 @@ 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 (flags & tf_error)
> - constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> - "%qD defined %<thread_local%> in "
> - "%<constexpr%> context", tmp);
> - return false;
> - }
> - else if (TREE_STATIC (tmp))
> + if (TREE_STATIC (tmp)
> + || (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp)))
> {
> - if (flags & tf_error)
> - constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> - "%qD defined %<static%> in %<constexpr%> "
> - "context", tmp);
> - return false;
> + bool ok = (processing_template_decl
> + ? decl_maybe_constant_var_p (tmp)
> + : decl_constant_var_p (tmp));
> + /* Since P2647R1 control can pass through definitions of static
> + or thread_local vars usable in constant expressions.
> + In C++20 or older, if such vars are declared inside of
> + constexpr or consteval function, diagnose_static_in_constexpr
> + should have already pedwarned on those. Otherwise they could
> + be e.g. in a statement expression, reject those before
> + C++23. */
> + if (ok && cxx_dialect < cxx23)
> + {
> + tree fnctx = decl_function_context (tmp);
> + if (fnctx == NULL_TREE
> + || !DECL_DECLARED_CONSTEXPR_P (fnctx))
> + ok = false;
> + }
> + if (!ok)
> + {
> + if (flags & tf_error)
> + {
> + if (CP_DECL_THREAD_LOCAL_P (tmp))
> + constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> + "%qD defined %<thread_local%> in "
> + "%<constexpr%> context", tmp);
> + else
> + constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
> + "%qD defined %<static%> in "
> + "%<constexpr%> context", tmp);
> + }
> + return false;
> + }
> }
> else if (!check_for_uninitialized_const_var
> (tmp, /*constexpr_context_p=*/true, flags))
> --- gcc/cp/decl.cc.jj 2022-11-16 14:44:43.692339668 +0100
> +++ gcc/cp/decl.cc 2022-11-17 20:53:44.102011594 +0100
> @@ -5600,6 +5600,57 @@ groktypename (cp_decl_specifier_seq *typ
> return type;
> }
>
> +/* For C++17 and older diagnose static or thread_local decls in constexpr
> + or consteval functions. For C++20 similarly, except if they are
> + usable in constant expressions. */
> +
> +static void
> +diagnose_static_in_constexpr (tree decl)
> +{
> + if (cxx_dialect >= cxx23)
> + return;
> + if (current_function_decl
> + && VAR_P (decl)
> + && DECL_DECLARED_CONSTEXPR_P (current_function_decl))
> + {
> + bool ok = false;
> + if (processing_template_decl
> + ? decl_maybe_constant_var_p (decl)
> + : decl_constant_var_p (decl))
> + {
> + if (CP_DECL_THREAD_LOCAL_P (decl) && !DECL_REALLY_EXTERN (decl))
> + pedwarn (DECL_SOURCE_LOCATION (decl), OPT_Wpedantic,
> + "%qD defined %<thread_local%> in %qs function only "
> + "available with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
> + DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
> + ? "consteval" : "constexpr");
> + else if (TREE_STATIC (decl))
> + pedwarn (DECL_SOURCE_LOCATION (decl), OPT_Wpedantic,
> + "%qD defined %<static%> in %qs function only available "
> + "with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
> + DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
> + ? "consteval" : "constexpr");
> + ok = true;
> + }
> + else if (CP_DECL_THREAD_LOCAL_P (decl) && !DECL_REALLY_EXTERN (decl))
> + error_at (DECL_SOURCE_LOCATION (decl),
> + "%qD defined %<thread_local%> in %qs function only "
> + "available with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
> + DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
> + ? "consteval" : "constexpr");
> + else if (TREE_STATIC (decl))
> + error_at (DECL_SOURCE_LOCATION (decl),
> + "%qD defined %<static%> in %qs function only available "
> + "with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
> + DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
> + ? "consteval" : "constexpr");
> + else
> + ok = true;
> + if (!ok)
> + cp_function_chain->invalid_constexpr = true;
> + }
> +}
> +
> /* Process a DECLARATOR for a function-scope or namespace-scope
> variable or function declaration.
> (Function definitions go through start_function; class member
> @@ -5860,29 +5911,6 @@ start_decl (const cp_declarator *declara
> DECL_THIS_STATIC (decl) = 1;
> }
>
> - if (current_function_decl && VAR_P (decl)
> - && DECL_DECLARED_CONSTEXPR_P (current_function_decl)
> - && cxx_dialect < cxx23)
> - {
> - bool ok = false;
> - if (CP_DECL_THREAD_LOCAL_P (decl) && !DECL_REALLY_EXTERN (decl))
> - error_at (DECL_SOURCE_LOCATION (decl),
> - "%qD defined %<thread_local%> in %qs function only "
> - "available with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
> - DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
> - ? "consteval" : "constexpr");
> - else if (TREE_STATIC (decl))
> - error_at (DECL_SOURCE_LOCATION (decl),
> - "%qD defined %<static%> in %qs function only available "
> - "with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
> - DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
> - ? "consteval" : "constexpr");
> - else
> - ok = true;
> - if (!ok)
> - cp_function_chain->invalid_constexpr = true;
> - }
> -
> if (!processing_template_decl && VAR_P (decl))
> start_decl_1 (decl, initialized);
>
> @@ -8424,6 +8452,9 @@ cp_finish_decl (tree decl, tree init, bo
> set_user_assembler_name (decl, asmspec);
> DECL_HARD_REGISTER (decl) = 1;
> }
> +
> + diagnose_static_in_constexpr (decl);
> +
> return;
> }
>
> @@ -8749,6 +8780,8 @@ cp_finish_decl (tree decl, tree init, bo
> && !DECL_HARD_REGISTER (decl))
> targetm.lower_local_decl_alignment (decl);
>
> + diagnose_static_in_constexpr (decl);
> +
> invoke_plugin_callbacks (PLUGIN_FINISH_DECL, decl);
> }
>
> --- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C.jj 2022-11-17 09:00:42.108248984 +0100
> +++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit17.C 2022-11-17 20:55:33.550498209 +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/constexpr-nonlit18.C.jj 2022-11-17 09:29:45.776136195 +0100
> +++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit18.C 2022-11-17 21:02:20.852865509 +0100
> @@ -0,0 +1,49 @@
> +// P2647R1 - Permitting static constexpr variables in constexpr functions
> +// { dg-do compile { target c++14 } }
> +
> +constexpr int
> +f1 (int x)
> +{
> + if (x)
> + throw 1;
> + return 0;
> +}
> +
> +constexpr int
> +f2 ()
> +{
> + static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0;
> +}
> +
> +constexpr int
> +f3 ()
> +{
> + static const int a = 5; // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0;
> +}
> +
> +constexpr int
> +f4 () // { dg-message "declared here" "" { target c++20_down } }
> +{ // { dg-message "is not usable as a 'constexpr' function because:" "" { target c++23 } .-1 }
> + static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0; // { dg-error "'a' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 }
> +}
> +
> +constexpr int a4 = f4 (); // { dg-error "called in a constant expression" }
> +
> +constexpr int
> +f5 ()
> +{
> + static const int a = f1 (0); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0;
> +}
> +
> +constexpr int
> +f6 ()
> +{
> + static const int a = f1 (0); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0;
> +}
> +
> +constexpr int a6 = f6 ();
> --- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit19.C.jj 2022-11-17 20:56:07.887023431 +0100
> +++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit19.C 2022-11-17 21:04:12.618319027 +0100
> @@ -0,0 +1,50 @@
> +// P2647R1 - Permitting static constexpr variables in constexpr functions
> +// { dg-do compile { target c++14 } }
> +// { dg-options "-pedantic" }
> +
> +constexpr int
> +f1 (int x)
> +{
> + if (x)
> + throw 1;
> + return 0;
> +}
> +
> +constexpr int
> +f2 ()
> +{
> + static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0;
> +}
> +
> +constexpr int
> +f3 ()
> +{
> + static const int a = 5; // { dg-warning "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0;
> +}
> +
> +constexpr int
> +f4 () // { dg-message "declared here" "" { target c++20_down } }
> +{ // { dg-message "is not usable as a 'constexpr' function because:" "" { target c++23 } .-1 }
> + static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0; // { dg-error "'a' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 }
> +}
> +
> +constexpr int a4 = f4 (); // { dg-error "called in a constant expression" }
> +
> +constexpr int
> +f5 ()
> +{
> + static const int a = f1 (0); // { dg-warning "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0;
> +}
> +
> +constexpr int
> +f6 ()
> +{
> + static const int a = f1 (0); // { dg-warning "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0;
> +}
> +
> +constexpr int a6 = f6 ();
> --- gcc/testsuite/g++.dg/cpp23/constexpr-nonlit20.C.jj 2022-11-17 20:56:28.527738024 +0100
> +++ gcc/testsuite/g++.dg/cpp23/constexpr-nonlit20.C 2022-11-17 21:31:25.209729268 +0100
> @@ -0,0 +1,50 @@
> +// P2647R1 - Permitting static constexpr variables in constexpr functions
> +// { dg-do compile { target c++14 } }
> +// { dg-options "-Wno-pedantic" }
> +
> +constexpr int
> +f1 (int x)
> +{
> + if (x)
> + throw 1;
> + return 0;
> +}
> +
> +constexpr int
> +f2 ()
> +{
> + static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0;
> +}
> +
> +constexpr int
> +f3 ()
> +{
> + static const int a = 5;
> + return 0;
> +}
> +
> +constexpr int
> +f4 () // { dg-message "declared here" "" { target c++20_down } }
> +{ // { dg-message "is not usable as a 'constexpr' function because:" "" { target c++23 } .-1 }
> + static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
> + return 0; // { dg-error "'a' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 }
> +}
> +
> +constexpr int a4 = f4 (); // { dg-error "called in a constant expression" }
> +
> +constexpr int
> +f5 ()
> +{
> + static const int a = f1 (0);
> + return 0;
> +}
> +
> +constexpr int
> +f6 ()
> +{
> + static const int a = f1 (0);
> + return 0;
> +}
> +
> +constexpr int a6 = f6 ();
> --- gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C.jj 2022-11-17 08:48:30.561356753 +0100
> +++ gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C 2022-11-17 09:00:42.108248984 +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 2022-11-17 08:48:02.730741221 +0100
> +++ gcc/testsuite/g++.dg/ext/stmtexpr19.C 2022-11-17 20:57:06.936206927 +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
>
On Thu, Nov 17, 2022 at 07:15:05PM -0500, Marek Polacek wrote:
> > --- gcc/cp/decl.cc.jj 2022-11-16 14:44:43.692339668 +0100
> > +++ gcc/cp/decl.cc 2022-11-17 20:53:44.102011594 +0100
> > @@ -5600,6 +5600,57 @@ groktypename (cp_decl_specifier_seq *typ
> > return type;
> > }
> >
> > +/* For C++17 and older diagnose static or thread_local decls in constexpr
> > + or consteval functions. For C++20 similarly, except if they are
>
> In C++17 we don't support consteval so I guess drop the "or consteval "?
I just forgot to update the function comment.
Anyway, I think:
> BTW, I notice that the patch breaks
> g++.dg/cpp1y/lambda-generic-func1.C
> g++.dg/cpp1z/constexpr-lambda16.C
> Maybe they just need dg- tweaks.
this is actually a real bug and I'm not sure how to resolve that.
We have there:
int main()
{
[](auto i) { if (i) { int j; static int k; return i + j; } return i; }(0);
}
and for C++17/20 I presume something (haven't figured out yet what) marks
the lambda operator() when still a template as constexpr and then
cp_finish_decl -> diagnose_static_in_constexpr pedwarns on it.
For the above perhaps we could figure out there is a static int k; in the
operator() and don't turn it into constexpr, but what if there is
something that would e.g. satisfy decl_maybe_constant_var_p but not
decl_constant_var_p when actually instantiated?
Without my patch, the diagnostics is in start_decl which isn't called again
during instantiation, so I presume we mark it as constexpr and then we'd
diagnose it during constant evaluation.
Jakub
On Fri, Nov 18, 2022 at 08:48:32AM +0100, Jakub Jelinek wrote:
> On Thu, Nov 17, 2022 at 07:15:05PM -0500, Marek Polacek wrote:
> > > --- gcc/cp/decl.cc.jj 2022-11-16 14:44:43.692339668 +0100
> > > +++ gcc/cp/decl.cc 2022-11-17 20:53:44.102011594 +0100
> > > @@ -5600,6 +5600,57 @@ groktypename (cp_decl_specifier_seq *typ
> > > return type;
> > > }
> > >
> > > +/* For C++17 and older diagnose static or thread_local decls in constexpr
> > > + or consteval functions. For C++20 similarly, except if they are
> >
> > In C++17 we don't support consteval so I guess drop the "or consteval "?
>
> I just forgot to update the function comment.
>
> Anyway, I think:
>
> > BTW, I notice that the patch breaks
> > g++.dg/cpp1y/lambda-generic-func1.C
> > g++.dg/cpp1z/constexpr-lambda16.C
> > Maybe they just need dg- tweaks.
>
> this is actually a real bug and I'm not sure how to resolve that.
>
> We have there:
>
> int main()
> {
> [](auto i) { if (i) { int j; static int k; return i + j; } return i; }(0);
> }
>
> and for C++17/20 I presume something (haven't figured out yet what) marks
Right, that's the C++17 implicit constexpr for lambdas, finish_function:
/* Lambda closure members are implicitly constexpr if possible. */
if (cxx_dialect >= cxx17
&& LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl)))
DECL_DECLARED_CONSTEXPR_P (fndecl)
= ((processing_template_decl
|| is_valid_constexpr_fn (fndecl, /*complain*/false))
&& potential_constant_expression (DECL_SAVED_TREE (fndecl)));
> the lambda operator() when still a template as constexpr and then
> cp_finish_decl -> diagnose_static_in_constexpr pedwarns on it.
> For the above perhaps we could figure out there is a static int k; in the
> operator() and don't turn it into constexpr, but what if there is
> something that would e.g. satisfy decl_maybe_constant_var_p but not
> decl_constant_var_p when actually instantiated?
> Without my patch, the diagnostics is in start_decl which isn't called again
> during instantiation, so I presume we mark it as constexpr and then we'd
> diagnose it during constant evaluation.
Um, can we give up on trying to handle C++17/C++20 then?
Marek
On Fri, Nov 18, 2022 at 10:03:18AM -0500, Marek Polacek wrote:
> > the lambda operator() when still a template as constexpr and then
> > cp_finish_decl -> diagnose_static_in_constexpr pedwarns on it.
> > For the above perhaps we could figure out there is a static int k; in the
> > operator() and don't turn it into constexpr, but what if there is
> > something that would e.g. satisfy decl_maybe_constant_var_p but not
> > decl_constant_var_p when actually instantiated?
> > Without my patch, the diagnostics is in start_decl which isn't called again
> > during instantiation, so I presume we mark it as constexpr and then we'd
> > diagnose it during constant evaluation.
>
> Um, can we give up on trying to handle C++17/C++20 then?
That was why I've posted the other two variant patches (with the 3rd one
being a strict C++23 only change). Even if it is just a temporary state,
make C++23 work first and then iterate if it is possible to make C++17/20
working with the pedwarns right.
Jakub
On 11/18/22 10:03, Marek Polacek wrote:
> On Fri, Nov 18, 2022 at 08:48:32AM +0100, Jakub Jelinek wrote:
>> On Thu, Nov 17, 2022 at 07:15:05PM -0500, Marek Polacek wrote:
>>>> --- gcc/cp/decl.cc.jj 2022-11-16 14:44:43.692339668 +0100
>>>> +++ gcc/cp/decl.cc 2022-11-17 20:53:44.102011594 +0100
>>>> @@ -5600,6 +5600,57 @@ groktypename (cp_decl_specifier_seq *typ
>>>> return type;
>>>> }
>>>>
>>>> +/* For C++17 and older diagnose static or thread_local decls in constexpr
>>>> + or consteval functions. For C++20 similarly, except if they are
>>>
>>> In C++17 we don't support consteval so I guess drop the "or consteval "?
>>
>> I just forgot to update the function comment.
>>
>> Anyway, I think:
>>
>>> BTW, I notice that the patch breaks
>>> g++.dg/cpp1y/lambda-generic-func1.C
>>> g++.dg/cpp1z/constexpr-lambda16.C
>>> Maybe they just need dg- tweaks.
>>
>> this is actually a real bug and I'm not sure how to resolve that.
>>
>> We have there:
>>
>> int main()
>> {
>> [](auto i) { if (i) { int j; static int k; return i + j; } return i; }(0);
>> }
>>
>> and for C++17/20 I presume something (haven't figured out yet what) marks
>
> Right, that's the C++17 implicit constexpr for lambdas, finish_function:
>
> /* Lambda closure members are implicitly constexpr if possible. */
> if (cxx_dialect >= cxx17
> && LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl)))
> DECL_DECLARED_CONSTEXPR_P (fndecl)
> = ((processing_template_decl
> || is_valid_constexpr_fn (fndecl, /*complain*/false))
> && potential_constant_expression (DECL_SAVED_TREE (fndecl)));
Yeah, I guess potential_constant_expression needs to be stricter in a
lambda. Or perhaps any function that isn't already
DECL_DECLARED_CONSTEXPR_P?
>> the lambda operator() when still a template as constexpr and then
>> cp_finish_decl -> diagnose_static_in_constexpr pedwarns on it.
>> For the above perhaps we could figure out there is a static int k; in the
>> operator() and don't turn it into constexpr, but what if there is
>> something that would e.g. satisfy decl_maybe_constant_var_p but not
>> decl_constant_var_p when actually instantiated?
I'd expect the above change to potential_c_e to handle that case.
Jason
On Fri, Nov 18, 2022 at 11:24:45AM -0500, Jason Merrill wrote:
> > Right, that's the C++17 implicit constexpr for lambdas, finish_function:
> >
> > /* Lambda closure members are implicitly constexpr if possible. */
> > if (cxx_dialect >= cxx17
> > && LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl)))
> > DECL_DECLARED_CONSTEXPR_P (fndecl)
> > = ((processing_template_decl
> > || is_valid_constexpr_fn (fndecl, /*complain*/false))
> > && potential_constant_expression (DECL_SAVED_TREE (fndecl)));
>
> Yeah, I guess potential_constant_expression needs to be stricter in a
> lambda. Or perhaps any function that isn't already
> DECL_DECLARED_CONSTEXPR_P?
potential_constant_expression can't be relied on that it catches up
everything if it, even a simple if statement with a condition not yet
known to be 0 or non-0 results in just a requirement that at least
one of the substatements is potential constant, etc.
Similarly switch statements etc.
If there is a way to distinguish between functions with user
specified constexpr/consteval and DECL_DECLARED_CONSTEXPR_P set
through the above if condition, sure, cp_finish_decl ->
check_static_in_constexpr could be perhaps silent about those, but then
we want to diagnose it during constexpr evaluation at least. But in that
case having it a pedwarn rather than "this is a constant expression"
vs. "this is not a constant expression, if !ctx->quiet emit an error"
is something I don't see how to handle. Because something needs
to be returned, it is a constant expression or it is not.
Jakub
On 11/18/22 11:34, Jakub Jelinek wrote:
> On Fri, Nov 18, 2022 at 11:24:45AM -0500, Jason Merrill wrote:
>>> Right, that's the C++17 implicit constexpr for lambdas, finish_function:
>>>
>>> /* Lambda closure members are implicitly constexpr if possible. */
>>> if (cxx_dialect >= cxx17
>>> && LAMBDA_TYPE_P (CP_DECL_CONTEXT (fndecl)))
>>> DECL_DECLARED_CONSTEXPR_P (fndecl)
>>> = ((processing_template_decl
>>> || is_valid_constexpr_fn (fndecl, /*complain*/false))
>>> && potential_constant_expression (DECL_SAVED_TREE (fndecl)));
>>
>> Yeah, I guess potential_constant_expression needs to be stricter in a
>> lambda. Or perhaps any function that isn't already
>> DECL_DECLARED_CONSTEXPR_P?
>
> potential_constant_expression can't be relied on that it catches up
> everything if it, even a simple if statement with a condition not yet
> known to be 0 or non-0 results in just a requirement that at least
> one of the substatements is potential constant, etc.
> Similarly switch statements etc.
> If there is a way to distinguish between functions with user
> specified constexpr/consteval and DECL_DECLARED_CONSTEXPR_P set
> through the above if condition, sure, cp_finish_decl ->
> check_static_in_constexpr could be perhaps silent about those, but then
> we want to diagnose it during constexpr evaluation at least. But in that
> case having it a pedwarn rather than "this is a constant expression"
> vs. "this is not a constant expression, if !ctx->quiet emit an error"
> is something I don't see how to handle. Because something needs
> to be returned, it is a constant expression or it is not.
True. Let's go with your option 2, then, thanks.
Jason
@@ -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=202211L");
cpp_define (pfile, "__cpp_named_character_escapes=202207L");
cpp_define (pfile, "__cpp_static_call_operator=202207L");
@@ -7100,17 +7100,35 @@ cxx_eval_constant_expression (const cons
/* Allow __FUNCTION__ etc. */
&& !DECL_ARTIFICIAL (r))
{
- if (!ctx->quiet)
+ bool ok = decl_constant_var_p (r);
+ /* Since P2647R1 control can pass through definitions of static
+ or thread_local vars usable in constant expressions.
+ In C++20 or older, if such vars are declared inside of
+ constexpr or consteval function, diagnose_static_in_constexpr
+ should have already pedwarned on those. Otherwise they could
+ be e.g. in a statement expression, reject those before
+ C++23. */
+ if (ok && cxx_dialect < cxx23)
{
- if (CP_DECL_THREAD_LOCAL_P (r))
- error_at (loc, "control passes through definition of %qD "
- "with thread storage duration", r);
- else
- error_at (loc, "control passes through definition of %qD "
- "with static storage duration", r);
+ tree fnctx = decl_function_context (r);
+ if (fnctx == NULL_TREE
+ || !DECL_DECLARED_CONSTEXPR_P (fnctx))
+ ok = false;
+ }
+ if (!ok)
+ {
+ if (!ctx->quiet)
+ {
+ if (CP_DECL_THREAD_LOCAL_P (r))
+ error_at (loc, "control passes through definition of "
+ "%qD with thread storage duration", r);
+ else
+ error_at (loc, "control passes through definition of "
+ "%qD with static storage duration", r);
+ }
+ *non_constant_p = true;
+ break;
}
- *non_constant_p = true;
- break;
}
if (AGGREGATE_TYPE_P (TREE_TYPE (r))
@@ -9588,21 +9606,41 @@ 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 (flags & tf_error)
- constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
- "%qD defined %<thread_local%> in "
- "%<constexpr%> context", tmp);
- return false;
- }
- else if (TREE_STATIC (tmp))
+ if (TREE_STATIC (tmp)
+ || (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp)))
{
- if (flags & tf_error)
- constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
- "%qD defined %<static%> in %<constexpr%> "
- "context", tmp);
- return false;
+ bool ok = (processing_template_decl
+ ? decl_maybe_constant_var_p (tmp)
+ : decl_constant_var_p (tmp));
+ /* Since P2647R1 control can pass through definitions of static
+ or thread_local vars usable in constant expressions.
+ In C++20 or older, if such vars are declared inside of
+ constexpr or consteval function, diagnose_static_in_constexpr
+ should have already pedwarned on those. Otherwise they could
+ be e.g. in a statement expression, reject those before
+ C++23. */
+ if (ok && cxx_dialect < cxx23)
+ {
+ tree fnctx = decl_function_context (tmp);
+ if (fnctx == NULL_TREE
+ || !DECL_DECLARED_CONSTEXPR_P (fnctx))
+ ok = false;
+ }
+ if (!ok)
+ {
+ if (flags & tf_error)
+ {
+ if (CP_DECL_THREAD_LOCAL_P (tmp))
+ constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
+ "%qD defined %<thread_local%> in "
+ "%<constexpr%> context", tmp);
+ else
+ constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p,
+ "%qD defined %<static%> in "
+ "%<constexpr%> context", tmp);
+ }
+ return false;
+ }
}
else if (!check_for_uninitialized_const_var
(tmp, /*constexpr_context_p=*/true, flags))
@@ -5600,6 +5600,57 @@ groktypename (cp_decl_specifier_seq *typ
return type;
}
+/* For C++17 and older diagnose static or thread_local decls in constexpr
+ or consteval functions. For C++20 similarly, except if they are
+ usable in constant expressions. */
+
+static void
+diagnose_static_in_constexpr (tree decl)
+{
+ if (cxx_dialect >= cxx23)
+ return;
+ if (current_function_decl
+ && VAR_P (decl)
+ && DECL_DECLARED_CONSTEXPR_P (current_function_decl))
+ {
+ bool ok = false;
+ if (processing_template_decl
+ ? decl_maybe_constant_var_p (decl)
+ : decl_constant_var_p (decl))
+ {
+ if (CP_DECL_THREAD_LOCAL_P (decl) && !DECL_REALLY_EXTERN (decl))
+ pedwarn (DECL_SOURCE_LOCATION (decl), OPT_Wpedantic,
+ "%qD defined %<thread_local%> in %qs function only "
+ "available with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
+ DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
+ ? "consteval" : "constexpr");
+ else if (TREE_STATIC (decl))
+ pedwarn (DECL_SOURCE_LOCATION (decl), OPT_Wpedantic,
+ "%qD defined %<static%> in %qs function only available "
+ "with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
+ DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
+ ? "consteval" : "constexpr");
+ ok = true;
+ }
+ else if (CP_DECL_THREAD_LOCAL_P (decl) && !DECL_REALLY_EXTERN (decl))
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "%qD defined %<thread_local%> in %qs function only "
+ "available with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
+ DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
+ ? "consteval" : "constexpr");
+ else if (TREE_STATIC (decl))
+ error_at (DECL_SOURCE_LOCATION (decl),
+ "%qD defined %<static%> in %qs function only available "
+ "with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
+ DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
+ ? "consteval" : "constexpr");
+ else
+ ok = true;
+ if (!ok)
+ cp_function_chain->invalid_constexpr = true;
+ }
+}
+
/* Process a DECLARATOR for a function-scope or namespace-scope
variable or function declaration.
(Function definitions go through start_function; class member
@@ -5860,29 +5911,6 @@ start_decl (const cp_declarator *declara
DECL_THIS_STATIC (decl) = 1;
}
- if (current_function_decl && VAR_P (decl)
- && DECL_DECLARED_CONSTEXPR_P (current_function_decl)
- && cxx_dialect < cxx23)
- {
- bool ok = false;
- if (CP_DECL_THREAD_LOCAL_P (decl) && !DECL_REALLY_EXTERN (decl))
- error_at (DECL_SOURCE_LOCATION (decl),
- "%qD defined %<thread_local%> in %qs function only "
- "available with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
- DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
- ? "consteval" : "constexpr");
- else if (TREE_STATIC (decl))
- error_at (DECL_SOURCE_LOCATION (decl),
- "%qD defined %<static%> in %qs function only available "
- "with %<-std=c++2b%> or %<-std=gnu++2b%>", decl,
- DECL_IMMEDIATE_FUNCTION_P (current_function_decl)
- ? "consteval" : "constexpr");
- else
- ok = true;
- if (!ok)
- cp_function_chain->invalid_constexpr = true;
- }
-
if (!processing_template_decl && VAR_P (decl))
start_decl_1 (decl, initialized);
@@ -8424,6 +8452,9 @@ cp_finish_decl (tree decl, tree init, bo
set_user_assembler_name (decl, asmspec);
DECL_HARD_REGISTER (decl) = 1;
}
+
+ diagnose_static_in_constexpr (decl);
+
return;
}
@@ -8749,6 +8780,8 @@ cp_finish_decl (tree decl, tree init, bo
&& !DECL_HARD_REGISTER (decl))
targetm.lower_local_decl_alignment (decl);
+ diagnose_static_in_constexpr (decl);
+
invoke_plugin_callbacks (PLUGIN_FINISH_DECL, decl);
}
@@ -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 () == ' ');
@@ -0,0 +1,49 @@
+// P2647R1 - Permitting static constexpr variables in constexpr functions
+// { dg-do compile { target c++14 } }
+
+constexpr int
+f1 (int x)
+{
+ if (x)
+ throw 1;
+ return 0;
+}
+
+constexpr int
+f2 ()
+{
+ static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0;
+}
+
+constexpr int
+f3 ()
+{
+ static const int a = 5; // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0;
+}
+
+constexpr int
+f4 () // { dg-message "declared here" "" { target c++20_down } }
+{ // { dg-message "is not usable as a 'constexpr' function because:" "" { target c++23 } .-1 }
+ static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0; // { dg-error "'a' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 }
+}
+
+constexpr int a4 = f4 (); // { dg-error "called in a constant expression" }
+
+constexpr int
+f5 ()
+{
+ static const int a = f1 (0); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0;
+}
+
+constexpr int
+f6 ()
+{
+ static const int a = f1 (0); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0;
+}
+
+constexpr int a6 = f6 ();
@@ -0,0 +1,50 @@
+// P2647R1 - Permitting static constexpr variables in constexpr functions
+// { dg-do compile { target c++14 } }
+// { dg-options "-pedantic" }
+
+constexpr int
+f1 (int x)
+{
+ if (x)
+ throw 1;
+ return 0;
+}
+
+constexpr int
+f2 ()
+{
+ static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0;
+}
+
+constexpr int
+f3 ()
+{
+ static const int a = 5; // { dg-warning "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0;
+}
+
+constexpr int
+f4 () // { dg-message "declared here" "" { target c++20_down } }
+{ // { dg-message "is not usable as a 'constexpr' function because:" "" { target c++23 } .-1 }
+ static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0; // { dg-error "'a' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 }
+}
+
+constexpr int a4 = f4 (); // { dg-error "called in a constant expression" }
+
+constexpr int
+f5 ()
+{
+ static const int a = f1 (0); // { dg-warning "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0;
+}
+
+constexpr int
+f6 ()
+{
+ static const int a = f1 (0); // { dg-warning "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0;
+}
+
+constexpr int a6 = f6 ();
@@ -0,0 +1,50 @@
+// P2647R1 - Permitting static constexpr variables in constexpr functions
+// { dg-do compile { target c++14 } }
+// { dg-options "-Wno-pedantic" }
+
+constexpr int
+f1 (int x)
+{
+ if (x)
+ throw 1;
+ return 0;
+}
+
+constexpr int
+f2 ()
+{
+ static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0;
+}
+
+constexpr int
+f3 ()
+{
+ static const int a = 5;
+ return 0;
+}
+
+constexpr int
+f4 () // { dg-message "declared here" "" { target c++20_down } }
+{ // { dg-message "is not usable as a 'constexpr' function because:" "" { target c++23 } .-1 }
+ static const int a = f1 (1); // { dg-error "'a' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } }
+ return 0; // { dg-error "'a' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 }
+}
+
+constexpr int a4 = f4 (); // { dg-error "called in a constant expression" }
+
+constexpr int
+f5 ()
+{
+ static const int a = f1 (0);
+ return 0;
+}
+
+constexpr int
+f6 ()
+{
+ static const int a = f1 (0);
+ return 0;
+}
+
+constexpr int a6 = f6 ();
@@ -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
@@ -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;