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[130.44.159.43]) by smtp.gmail.com with ESMTPSA id y8-20020a05620a44c800b006ee77f1ecc3sm7393174qkp.31.2022.11.14.15.00.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Nov 2022 15:00:59 -0800 (PST) Message-ID: <5cfabd39-8afe-931c-7872-1b4360d2e5b5@redhat.com> Date: Mon, 14 Nov 2022 18:00:58 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH] c++: P2448 - Relaxing some constexpr restrictions [PR106649] To: Marek Polacek , GCC Patches References: <20221109205305.96262-1-polacek@redhat.com> From: Jason Merrill In-Reply-To: <20221109205305.96262-1-polacek@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.5 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,KAM_SHORT,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 11/9/22 10:53, Marek Polacek wrote: > This patch implements C++23 P2448, which lifts more restrictions on the > constexpr keyword. It's effectively going the way of being just a hint > (hello, inline!). > > This gist is relatively simple: in C++23, a constexpr function's return > type/parameter type doesn't have to be a literal type; and you can have > a constexpr function for which no invocation satisfies the requirements > of a core constant expression. For example, > > void f(int& i); // not constexpr > > constexpr void g(int& i) { > f(i); // unconditionally calls a non-constexpr function > } > > is now OK, even though there isn't an invocation of 'g' that would be > a constant expression. Maybe 'f' will be made constexpr soon, or maybe > this depends on the version of C++ used, and similar. The patch is > unfortunately not that trivial. The important bit is to use the new > require_potential_rvalue_constant_expression_fncheck in > maybe_save_constexpr_fundef (and where appropriate). It has a new flag > that says that we're checking the body of a constexpr function, and in > that case it's OK to find constructs that aren't a constant expression. > > Since it's useful to be able to check for problematic constructs even > in C++23, this patch implements a new warning, -Winvalid-constexpr, > which is a pedwarn turned on by default in C++20 and earlier, and which > can be turned on in C++23 as well, in which case it's an ordinary warning. > This I implemented by using the new function constexpr_error, used in > p_c_e_1 and friends. (In some cases I believe fundef_p will be always > false (= hard error), but it made sense to me to be consistent and use > constexpr_error throughout p_c_e_1.) > > While working on this I think I found a bug, see constexpr-nonlit15.C > and . This patch doesn't address that. > > I also don't love that in C++23, if you don't use -Winvalid-constexpr, > and call a constexpr function that in fact isn't constexpr-ready yet, > sometimes all you get is an error saying "called in a constant expression" > like in constexpr-nonlit12.C. This could be remedied by some tweaks to > explain_invalid_constexpr_fn, I reckon (it gives up on !DECL_DEFAULTED_FN). And also in maybe_save_constexpr_fn: if -Wno-invalid-constexpr, "complain" should be false so we save the definition for explain_invalid_constexpr_fn to refer to. > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > PR c++/106649 > > gcc/c-family/ChangeLog: > > * c-cppbuiltin.cc (c_cpp_builtins): Update value of __cpp_constexpr for > C++23. > * c-opts.cc (c_common_post_options): Set warn_invalid_constexpr > depending on cxx_dialect. > * c.opt (Winvalid-constexpr): New option. > > gcc/cp/ChangeLog: > > * constexpr.cc (constexpr_error): New function. > (is_valid_constexpr_fn): Use constexpr_error. > (maybe_save_constexpr_fundef): Call > require_potential_rvalue_constant_expression_fncheck rather than > require_potential_rvalue_constant_expression. > (non_const_var_error): Add a bool parameter. Use constexpr_error. > (inline_asm_in_constexpr_error): Likewise. > (cxx_eval_constant_expression): Adjust calls to non_const_var_error > and inline_asm_in_constexpr_error. > (potential_constant_expression_1): Add a bool parameter. Use > constexpr_error. > (require_potential_rvalue_constant_expression_fncheck): New function. > * cp-tree.h (require_potential_rvalue_constant_expression_fncheck): > Declare. > * method.cc (struct comp_info): Call > require_potential_rvalue_constant_expression_fncheck rather than > require_potential_rvalue_constant_expression. > > gcc/ChangeLog: > > * doc/gcc/gcc-command-options/option-summary.rst: Add > -Winvalid-constexpr. > * doc/gcc/gcc-command-options/options-controlling-c++-dialect.rst: > Document -Winvalid-constexpr. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp0x/constexpr-ctor2.C: Expect an error in c++20_down only. > * g++.dg/cpp0x/constexpr-default-ctor.C: Likewise. > * g++.dg/cpp0x/constexpr-diag3.C: Likewise. > * g++.dg/cpp0x/constexpr-ex1.C: Likewise. > * g++.dg/cpp0x/constexpr-friend.C: Likewise. > * g++.dg/cpp0x/constexpr-generated1.C: Likewise. > * g++.dg/cpp0x/constexpr-ice5.C: Likewise. > * g++.dg/cpp0x/constexpr-ice6.C: Likewise. > * g++.dg/cpp0x/constexpr-memfn1.C: Likewise. > * g++.dg/cpp0x/constexpr-neg2.C: Likewise. > * g++.dg/cpp0x/constexpr-non-const-arg.C: Likewise. > * g++.dg/cpp0x/constexpr-reinterpret1.C: Likewise. > * g++.dg/cpp0x/pr65327.C: Likewise. > * g++.dg/cpp1y/constexpr-105050.C: Likewise. > * g++.dg/cpp1y/constexpr-89285-2.C: Likewise. > * g++.dg/cpp1y/constexpr-89285.C: Likewise. > * g++.dg/cpp1y/constexpr-89785-2.C: Likewise. > * g++.dg/cpp1y/constexpr-local4.C: Likewise. > * g++.dg/cpp1y/constexpr-neg1.C: Likewise. > * g++.dg/cpp1y/constexpr-nsdmi7b.C: Likewise. > * g++.dg/cpp1y/constexpr-throw.C: Likewise. > * g++.dg/cpp23/constexpr-nonlit3.C: Remove dg-error. > * g++.dg/cpp23/constexpr-nonlit6.C: Expect an error in c++20_down only. > Call the test functions. > * g++.dg/cpp23/feat-cxx2b.C: Adjust the expected value of > __cpp_constexpr. > * g++.dg/cpp2a/consteval3.C: Remove dg-error. > * g++.dg/cpp2a/constexpr-new7.C: Expect an error in c++20_down only. > * g++.dg/cpp2a/constexpr-try5.C: Remove dg-error. > * g++.dg/cpp2a/spaceship-constexpr1.C: Expect an error in c++20_down > only. > * g++.dg/cpp2a/spaceship-eq3.C: Likewise. > * g++.dg/diagnostic/constexpr1.C: Remove dg-error. > * g++.dg/gomp/pr79664.C: Use -Winvalid-constexpr -pedantic-errors. > * g++.dg/ubsan/vptr-4.C: Likewise. > * g++.dg/cpp23/constexpr-nonlit10.C: New test. > * g++.dg/cpp23/constexpr-nonlit11.C: New test. > * g++.dg/cpp23/constexpr-nonlit12.C: New test. > * g++.dg/cpp23/constexpr-nonlit13.C: New test. > * g++.dg/cpp23/constexpr-nonlit14.C: New test. > * g++.dg/cpp23/constexpr-nonlit15.C: New test. > * g++.dg/cpp23/constexpr-nonlit16.C: New test. > * g++.dg/cpp23/constexpr-nonlit8.C: New test. > * g++.dg/cpp23/constexpr-nonlit9.C: New test. > --- > gcc/c-family/c-cppbuiltin.cc | 2 +- > gcc/c-family/c-opts.cc | 4 + > gcc/c-family/c.opt | 4 + > gcc/cp/constexpr.cc | 272 ++++++++++++------ > gcc/cp/cp-tree.h | 1 + > gcc/cp/method.cc | 8 +- > .../gcc-command-options/option-summary.rst | 2 +- > .../options-controlling-c++-dialect.rst | 28 ++ > gcc/testsuite/g++.dg/cpp0x/constexpr-ctor2.C | 2 +- > .../g++.dg/cpp0x/constexpr-default-ctor.C | 6 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-diag3.C | 2 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-ex1.C | 2 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-friend.C | 2 +- > .../g++.dg/cpp0x/constexpr-generated1.C | 2 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-ice5.C | 2 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-ice6.C | 4 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-memfn1.C | 4 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-neg2.C | 6 +- > .../g++.dg/cpp0x/constexpr-non-const-arg.C | 2 +- > .../g++.dg/cpp0x/constexpr-reinterpret1.C | 2 +- > gcc/testsuite/g++.dg/cpp0x/pr65327.C | 2 +- > gcc/testsuite/g++.dg/cpp1y/constexpr-105050.C | 2 +- > .../g++.dg/cpp1y/constexpr-89285-2.C | 2 +- > gcc/testsuite/g++.dg/cpp1y/constexpr-89285.C | 2 +- > .../g++.dg/cpp1y/constexpr-89785-2.C | 4 +- > gcc/testsuite/g++.dg/cpp1y/constexpr-local4.C | 2 +- > gcc/testsuite/g++.dg/cpp1y/constexpr-neg1.C | 2 +- > .../g++.dg/cpp1y/constexpr-nsdmi7b.C | 2 +- > gcc/testsuite/g++.dg/cpp1y/constexpr-throw.C | 6 +- > .../g++.dg/cpp23/constexpr-nonlit10.C | 96 +++++++ > .../g++.dg/cpp23/constexpr-nonlit11.C | 53 ++++ > .../g++.dg/cpp23/constexpr-nonlit12.C | 32 +++ > .../g++.dg/cpp23/constexpr-nonlit13.C | 14 + > .../g++.dg/cpp23/constexpr-nonlit14.C | 26 ++ > .../g++.dg/cpp23/constexpr-nonlit15.C | 43 +++ > .../g++.dg/cpp23/constexpr-nonlit16.C | 23 ++ > .../g++.dg/cpp23/constexpr-nonlit3.C | 2 +- > .../g++.dg/cpp23/constexpr-nonlit6.C | 19 +- > .../g++.dg/cpp23/constexpr-nonlit8.C | 96 +++++++ > .../g++.dg/cpp23/constexpr-nonlit9.C | 53 ++++ > gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C | 4 +- > gcc/testsuite/g++.dg/cpp2a/consteval3.C | 1 - > gcc/testsuite/g++.dg/cpp2a/constexpr-new7.C | 4 +- > gcc/testsuite/g++.dg/cpp2a/constexpr-try5.C | 2 - > .../g++.dg/cpp2a/spaceship-constexpr1.C | 2 +- > gcc/testsuite/g++.dg/cpp2a/spaceship-eq3.C | 4 +- > gcc/testsuite/g++.dg/diagnostic/constexpr1.C | 2 - > gcc/testsuite/g++.dg/gomp/pr79664.C | 2 +- > gcc/testsuite/g++.dg/ubsan/vptr-4.C | 2 +- > 49 files changed, 717 insertions(+), 144 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/cpp23/constexpr-nonlit10.C > create mode 100644 gcc/testsuite/g++.dg/cpp23/constexpr-nonlit11.C > create mode 100644 gcc/testsuite/g++.dg/cpp23/constexpr-nonlit12.C > create mode 100644 gcc/testsuite/g++.dg/cpp23/constexpr-nonlit13.C > create mode 100644 gcc/testsuite/g++.dg/cpp23/constexpr-nonlit14.C > create mode 100644 gcc/testsuite/g++.dg/cpp23/constexpr-nonlit15.C > create mode 100644 gcc/testsuite/g++.dg/cpp23/constexpr-nonlit16.C > create mode 100644 gcc/testsuite/g++.dg/cpp23/constexpr-nonlit8.C > create mode 100644 gcc/testsuite/g++.dg/cpp23/constexpr-nonlit9.C > > diff --git a/gcc/c-family/c-cppbuiltin.cc b/gcc/c-family/c-cppbuiltin.cc > index cdb658f6ac9..08f7f6d5f75 100644 > --- a/gcc/c-family/c-cppbuiltin.cc > +++ b/gcc/c-family/c-cppbuiltin.cc > @@ -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=202110L"); > + cpp_define (pfile, "__cpp_constexpr=202207L"); > cpp_define (pfile, "__cpp_multidimensional_subscript=202110L"); > cpp_define (pfile, "__cpp_named_character_escapes=202207L"); > cpp_define (pfile, "__cpp_static_call_operator=202207L"); > diff --git a/gcc/c-family/c-opts.cc b/gcc/c-family/c-opts.cc > index 9e0494b2a45..94e92dc56b9 100644 > --- a/gcc/c-family/c-opts.cc > +++ b/gcc/c-family/c-opts.cc > @@ -1059,6 +1059,10 @@ c_common_post_options (const char **pfilename) > if (flag_sized_deallocation == -1) > flag_sized_deallocation = (cxx_dialect >= cxx14); > > + /* Pedwarn about invalid constexpr functions before C++23. */ > + if (warn_invalid_constexpr == -1) > + warn_invalid_constexpr = (cxx_dialect < cxx23); > + > /* char8_t support is implicitly enabled in C++20 and C2X. */ > if (flag_char8_t == -1) > flag_char8_t = (cxx_dialect >= cxx20) || flag_isoc2x; > diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt > index 63a300ecd7c..3daeab85531 100644 > --- a/gcc/c-family/c.opt > +++ b/gcc/c-family/c.opt > @@ -817,6 +817,10 @@ Wint-to-pointer-cast > C ObjC C++ ObjC++ Var(warn_int_to_pointer_cast) Init(1) Warning > Warn when there is a cast to a pointer from an integer of a different size. > > +Winvalid-constexpr > +C++ ObjC++ Var(warn_invalid_constexpr) Init(-1) Warning > +Warn when a function never produces a constant expression. > + > Winvalid-offsetof > C++ ObjC++ Var(warn_invalid_offsetof) Init(1) Warning > Warn about invalid uses of the \"offsetof\" macro. > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc > index 15b4f2c4a08..5641b72cd30 100644 > --- a/gcc/cp/constexpr.cc > +++ b/gcc/cp/constexpr.cc > @@ -139,6 +139,42 @@ ensure_literal_type_for_constexpr_object (tree decl) > return decl; > } > > +/* Issue a diagnostic with text GMSGID for constructs that are invalid in > + constexpr functions. CONSTEXPR_FUNDEF_P is true if we're checking > + a constexpr function body; if so, don't report hard errors and issue > + a pedwarn pre-C++23, or a warning in C++23, if requested by > + -Winvalid-constexpr. Otherwise, we're not in the context where we are > + checking if a function can be marked 'constexpr', so give a hard error. */ > + > +ATTRIBUTE_GCC_DIAG(3,4) > +static bool > +constexpr_error (location_t location, bool constexpr_fundef_p, > + const char *gmsgid, ...) > +{ > + diagnostic_info diagnostic; > + va_list ap; > + rich_location richloc (line_table, location); > + va_start (ap, gmsgid); > + bool ret; > + if (!constexpr_fundef_p) > + { > + /* Report an error that cannot be suppressed. */ > + diagnostic_set_info (&diagnostic, gmsgid, &ap, &richloc, DK_ERROR); > + ret = diagnostic_report_diagnostic (global_dc, &diagnostic); > + } > + else if (warn_invalid_constexpr) > + { > + diagnostic_set_info (&diagnostic, gmsgid, &ap, &richloc, > + cxx_dialect < cxx23 ? DK_PEDWARN : DK_WARNING); > + diagnostic.option_index = OPT_Winvalid_constexpr; > + ret = diagnostic_report_diagnostic (global_dc, &diagnostic); > + } > + else > + ret = false; > + va_end (ap); > + return ret; > +} > + > struct constexpr_fundef_hasher : ggc_ptr_hash > { > static hashval_t hash (const constexpr_fundef *); > @@ -208,9 +244,11 @@ is_valid_constexpr_fn (tree fun, bool complain) > if (complain) > { > auto_diagnostic_group d; > - error ("invalid type for parameter %d of % " > - "function %q+#D", DECL_PARM_INDEX (parm), fun); > - explain_non_literal_class (TREE_TYPE (parm)); > + if (constexpr_error (input_location, /*constexpr_fundef_p*/true, > + "invalid type for parameter %d of " > + "% function %q+#D", > + DECL_PARM_INDEX (parm), fun)) > + explain_non_literal_class (TREE_TYPE (parm)); > } > } > } > @@ -242,9 +280,10 @@ is_valid_constexpr_fn (tree fun, bool complain) > if (complain) > { > auto_diagnostic_group d; > - error ("invalid return type %qT of % function %q+D", > - rettype, fun); > - explain_non_literal_class (rettype); > + if (constexpr_error (input_location, /*constexpr_fundef_p*/true, > + "invalid return type %qT of % " > + "function %q+D", rettype, fun)) > + explain_non_literal_class (rettype); > } > } > > @@ -918,7 +957,7 @@ maybe_save_constexpr_fundef (tree fun) > > bool potential = potential_rvalue_constant_expression (massaged); > if (!potential && complain) > - require_potential_rvalue_constant_expression (massaged); > + require_potential_rvalue_constant_expression_fncheck (massaged); > > if (DECL_CONSTRUCTOR_P (fun) && potential > && !DECL_DEFAULTED_FN (fun)) > @@ -933,7 +972,7 @@ maybe_save_constexpr_fundef (tree fun) > massaged = DECL_SAVED_TREE (fun); > potential = potential_rvalue_constant_expression (massaged); > if (!potential && complain) > - require_potential_rvalue_constant_expression (massaged); > + require_potential_rvalue_constant_expression_fncheck (massaged); > } > } > > @@ -5612,11 +5651,12 @@ cxx_eval_indirect_ref (const constexpr_ctx *ctx, tree t, > } > > /* Complain about R, a VAR_DECL, not being usable in a constant expression. > + FUNDEF_P is true if we're checking a constexpr function body. > Shared between potential_constant_expression and > cxx_eval_constant_expression. */ > > static void > -non_const_var_error (location_t loc, tree r) > +non_const_var_error (location_t loc, tree r, bool fundef_p) > { > auto_diagnostic_group d; > tree type = TREE_TYPE (r); > @@ -5625,20 +5665,21 @@ non_const_var_error (location_t loc, tree r) > || DECL_NAME (r) == heap_vec_uninit_identifier > || DECL_NAME (r) == heap_vec_identifier) > { > - error_at (loc, "the content of uninitialized storage is not usable " > - "in a constant expression"); > - inform (DECL_SOURCE_LOCATION (r), "allocated here"); > + if (constexpr_error (loc, fundef_p, "the content of uninitialized " > + "storage is not usable in a constant expression")) > + inform (DECL_SOURCE_LOCATION (r), "allocated here"); > return; > } > if (DECL_NAME (r) == heap_deleted_identifier) > { > - error_at (loc, "use of allocated storage after deallocation in a " > - "constant expression"); > - inform (DECL_SOURCE_LOCATION (r), "allocated here"); > + if (constexpr_error (loc, fundef_p, "use of allocated storage after " > + "deallocation in a constant expression")) > + inform (DECL_SOURCE_LOCATION (r), "allocated here"); > return; > } > - error_at (loc, "the value of %qD is not usable in a constant " > - "expression", r); > + if (!constexpr_error (loc, fundef_p, "the value of %qD is not usable in " > + "a constant expression", r)) > + return; > /* Avoid error cascade. */ > if (DECL_INITIAL (r) == error_mark_node) > return; > @@ -6697,15 +6738,17 @@ lookup_placeholder (const constexpr_ctx *ctx, value_cat lval, tree type) > return ob; > } > > -/* Complain about an attempt to evaluate inline assembly. */ > +/* Complain about an attempt to evaluate inline assembly. If FUNDEF_P is > + true, we're checking a constexpr function body. */ > > static void > -inline_asm_in_constexpr_error (location_t loc) > +inline_asm_in_constexpr_error (location_t loc, bool fundef_p) > { > auto_diagnostic_group d; > - error_at (loc, "inline assembly is not a constant expression"); > - inform (loc, "only unevaluated inline assembly is allowed in a " > - "% function in C++20"); > + if (constexpr_error (loc, fundef_p, "inline assembly is not a " > + "constant expression")) > + inform (loc, "only unevaluated inline assembly is allowed in a " > + "% function in C++20"); > } > > /* We're getting the constant value of DECL in a manifestly constant-evaluated > @@ -6983,7 +7026,7 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t, > if (DECL_P (r)) > { > if (!ctx->quiet) > - non_const_var_error (loc, r); > + non_const_var_error (loc, r, /*fundef_p*/false); > *non_constant_p = true; > } > break; > @@ -7874,7 +7917,7 @@ cxx_eval_constant_expression (const constexpr_ctx *ctx, tree t, > > case ASM_EXPR: > if (!ctx->quiet) > - inline_asm_in_constexpr_error (loc); > + inline_asm_in_constexpr_error (loc, /*constexpr_fundef_p*/false); > *non_constant_p = true; > return t; > > @@ -8759,7 +8802,8 @@ check_for_return_continue (tree *tp, int *walk_subtrees, void *data) > diagnostic as appropriate under control of FLAGS. If WANT_RVAL is true, > an lvalue-rvalue conversion is implied. If NOW is true, we want to > consider the expression in the current context, independent of constexpr > - substitution. > + substitution. If FUNDEF_P is true, we're checking a constexpr function body > + and hard errors should not be reported by constexpr_error. > > C++0x [expr.const] used to say > > @@ -8776,10 +8820,12 @@ check_for_return_continue (tree *tp, int *walk_subtrees, void *data) > > static bool > potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > - tsubst_flags_t flags, tree *jump_target) > + bool fundef_p, tsubst_flags_t flags, > + tree *jump_target) > { > #define RECUR(T,RV) \ > - potential_constant_expression_1 ((T), (RV), strict, now, flags, jump_target) > + potential_constant_expression_1 ((T), (RV), strict, now, fundef_p, flags, \ > + jump_target) > > enum { any = false, rval = true }; > int i; > @@ -8801,8 +8847,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (TREE_THIS_VOLATILE (t) && want_rval) > { > if (flags & tf_error) > - error_at (loc, "lvalue-to-rvalue conversion of a volatile lvalue " > - "%qE with type %qT", t, TREE_TYPE (t)); > + constexpr_error (loc, fundef_p, "lvalue-to-rvalue conversion of " > + "a volatile lvalue %qE with type %qT", t, > + TREE_TYPE (t)); > return false; > } > if (CONSTANT_CLASS_P (t)) > @@ -8861,7 +8908,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > /* An empty class has no data to read. */ > return true; > if (flags & tf_error) > - error ("%qE is not a constant expression", t); > + constexpr_error (input_location, fundef_p, > + "%qE is not a constant expression", t); > return false; > } > return true; > @@ -8910,7 +8958,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > { > /* fold_call_expr can't do anything with IFN calls. */ > if (flags & tf_error) > - error_at (loc, "call to internal function %qE", t); > + constexpr_error (loc, fundef_p, > + "call to internal function %qE", t); > return false; > } > } > @@ -8940,12 +8989,11 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > || !is_std_construct_at (current_function_decl)) > && !cxx_dynamic_cast_fn_p (fun)) > { > - if (flags & tf_error) > - { > - error_at (loc, "call to non-% function %qD", > - fun); > - explain_invalid_constexpr_fn (fun); > - } > + if ((flags & tf_error) > + && constexpr_error (loc, fundef_p, > + "call to non-% " > + "function %qD", fun)) > + explain_invalid_constexpr_fn (fun); > return false; > } > /* A call to a non-static member function takes the address > @@ -8962,8 +9010,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > constexpr substitution might not use the value. */ > bool sub_now = false; > if (!potential_constant_expression_1 (x, rval, strict, > - sub_now, flags, > - jump_target)) > + sub_now, fundef_p, > + flags, jump_target)) > return false; > i = 1; > } > @@ -8997,7 +9045,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > substitution might not use the value of the argument. */ > bool sub_now = false; > if (!potential_constant_expression_1 (x, rv, strict, > - sub_now, flags, jump_target)) > + sub_now, fundef_p, flags, > + jump_target)) > return false; > } > return true; > @@ -9035,9 +9084,10 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (flags & tf_error) > { > tree cap = DECL_CAPTURED_VARIABLE (t); > - error ("lambda capture of %qE is not a constant expression", > - cap); > - if (decl_constant_var_p (cap)) > + if (constexpr_error (input_location, fundef_p, > + "lambda capture of %qE is not a " > + "constant expression", cap) > + && decl_constant_var_p (cap)) > inform (input_location, "because it is used as a glvalue"); > } > return false; > @@ -9060,8 +9110,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > && COMPLETE_TYPE_P (TREE_TYPE (t)) > && !is_really_empty_class (TREE_TYPE (t), /*ignore_vptr*/false)) > { > - if (flags & tf_error) > - non_const_var_error (loc, t); > + if (flags & tf_error) > + non_const_var_error (loc, t, fundef_p); > return false; > } > return true; > @@ -9070,7 +9120,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (REINTERPRET_CAST_P (t)) > { > if (flags & tf_error) > - error_at (loc, "% is not a constant expression"); > + constexpr_error (loc, fundef_p, "% is not a " > + "constant expression"); > return false; > } > /* FALLTHRU */ > @@ -9092,8 +9143,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > && !integer_zerop (from)) > { > if (flags & tf_error) > - error_at (loc, > - "% from integer to pointer"); > + constexpr_error (loc, fundef_p, > + "% from integer to " > + "pointer"); > return false; > } > } > @@ -9165,7 +9217,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (!var_in_maybe_constexpr_fn (x)) > { > if (flags & tf_error) > - error_at (loc, "use of % in a constant expression"); > + constexpr_error (loc, fundef_p, "use of % in a " > + "constant expression"); > return false; > } > return true; > @@ -9313,8 +9366,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > /* In C++17 lambdas can be constexpr, don't give up yet. */ > return true; > else if (flags & tf_error) > - error_at (loc, "lambda-expression is not a constant expression " > - "before C++17"); > + constexpr_error (loc, fundef_p, "lambda-expression is not a " > + "constant expression before C++17"); > return false; > > case NEW_EXPR: > @@ -9325,8 +9378,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > /* In C++20, new-expressions are potentially constant. */ > return true; > else if (flags & tf_error) > - error_at (loc, "new-expression is not a constant expression " > - "before C++20"); > + constexpr_error (loc, fundef_p, "new-expression is not a " > + "constant expression before C++20"); > return false; > > case DYNAMIC_CAST_EXPR: > @@ -9375,12 +9428,13 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > case AT_ENCODE_EXPR: > fail: > if (flags & tf_error) > - error_at (loc, "expression %qE is not a constant expression", t); > + constexpr_error (loc, fundef_p, "expression %qE is not a constant " > + "expression", t); > return false; > > case ASM_EXPR: > if (flags & tf_error) > - inline_asm_in_constexpr_error (loc); > + inline_asm_in_constexpr_error (loc, fundef_p); > return false; > > case OBJ_TYPE_REF: > @@ -9388,8 +9442,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > /* In C++20 virtual calls can be constexpr, don't give up yet. */ > return true; > else if (flags & tf_error) > - error_at (loc, > - "virtual functions cannot be % before C++20"); > + constexpr_error (loc, fundef_p, "virtual functions cannot be " > + "% before C++20"); > return false; > > case TYPEID_EXPR: > @@ -9404,8 +9458,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > && TYPE_POLYMORPHIC_P (TREE_TYPE (e))) > { > if (flags & tf_error) > - error_at (loc, "% is not a constant expression " > - "because %qE is of polymorphic type", e); > + constexpr_error (loc, fundef_p, "% is not a " > + "constant expression because %qE is " > + "of polymorphic type", e); > return false; > } > return true; > @@ -9467,9 +9522,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > constant expression. */ > { > if (flags & tf_error) > - error_at (loc, > - "cast to non-integral type %qT in a constant expression", > - TREE_TYPE (t)); > + constexpr_error (loc, fundef_p, > + "cast to non-integral type %qT in a constant " > + "expression", TREE_TYPE (t)); > return false; > } > /* This might be a conversion from a class to a (potentially) literal > @@ -9525,15 +9580,17 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (CP_DECL_THREAD_LOCAL_P (tmp) && !DECL_REALLY_EXTERN (tmp)) > { > if (flags & tf_error) > - error_at (DECL_SOURCE_LOCATION (tmp), "%qD defined " > - "% in % context", tmp); > + constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p, > + "%qD defined % in " > + "% context", tmp); > return false; > } > else if (TREE_STATIC (tmp)) > { > if (flags & tf_error) > - error_at (DECL_SOURCE_LOCATION (tmp), "%qD defined " > - "% in % context", tmp); > + constexpr_error (DECL_SOURCE_LOCATION (tmp), fundef_p, > + "%qD defined % in % " > + "context", tmp); > return false; > } > else if (!check_for_uninitialized_const_var > @@ -9556,9 +9613,10 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (flags & tf_error) > { > auto_diagnostic_group d; > - error_at (loc, "temporary of non-literal type %qT in a " > - "constant expression", TREE_TYPE (t)); > - explain_non_literal_class (TREE_TYPE (t)); > + if (constexpr_error (loc, fundef_p, > + "temporary of non-literal type %qT in a " > + "constant expression", TREE_TYPE (t))) > + explain_non_literal_class (TREE_TYPE (t)); > } > return false; > } > @@ -9605,7 +9663,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (integer_zerop (denom)) > { > if (flags & tf_error) > - error ("division by zero is not a constant expression"); > + constexpr_error (input_location, fundef_p, > + "division by zero is not a constant expression"); > return false; > } > else > @@ -9706,7 +9765,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (COND_EXPR_IS_VEC_DELETE (t) && cxx_dialect < cxx20) > { > if (flags & tf_error) > - error_at (loc, "% is not a constant expression"); > + constexpr_error (loc, fundef_p, "% is not a " > + "constant expression"); > return false; > } > /* Fall through. */ > @@ -9736,7 +9796,7 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > { > tree this_jump_target = tmp; > if (potential_constant_expression_1 (TREE_OPERAND (t, i), > - want_rval, strict, now, > + want_rval, strict, now, fundef_p, > tf_none, &this_jump_target)) > { > if (returns (&this_jump_target)) > @@ -9774,9 +9834,11 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (flags & tf_error) > { > if (TREE_CODE (t) == IF_STMT) > - error_at (loc, "neither branch of % is a constant expression"); > + constexpr_error (loc, fundef_p, "neither branch of % is a " > + "constant expression"); > else > - error_at (loc, "expression %qE is not a constant expression", t); > + constexpr_error (loc, fundef_p, "expression %qE is not a " > + "constant expression", t); > } > return false; > > @@ -9785,8 +9847,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > return true; > if (flags & tf_error) > { > - error_at (loc, "non-constant array initialization"); > - diagnose_non_constexpr_vec_init (t); > + if (constexpr_error (loc, fundef_p, "non-constant array " > + "initialization")) > + diagnose_non_constexpr_vec_init (t); > } > return false; > > @@ -9815,7 +9878,8 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > return true; > } > if (flags & tf_error) > - error_at (loc, "% is not a constant expression"); > + constexpr_error (loc, fundef_p, "% is not a constant " > + "expression"); > return false; > } > > @@ -9824,8 +9888,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > if (DECL_ARTIFICIAL (t) || cxx_dialect >= cxx23) > return true; > else if (flags & tf_error) > - error_at (loc, "label definition in % function only " > - "available with %<-std=c++2b%> or %<-std=gnu++2b%>"); > + constexpr_error (loc, fundef_p, "label definition in % " > + "function only available with %<-std=c++2b%> or " > + "%<-std=gnu++2b%>"); > return false; > > case ANNOTATE_EXPR: > @@ -9863,7 +9928,7 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > > bool > potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > - tsubst_flags_t flags) > + bool fundef_p, tsubst_flags_t flags) > { > if (flags & tf_error) > { > @@ -9871,13 +9936,14 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > efficiently in some cases (currently only for TRUTH_*_EXPR). If > that fails, replay the check noisily to give errors. */ > flags &= ~tf_error; > - if (potential_constant_expression_1 (t, want_rval, strict, now, flags)) > + if (potential_constant_expression_1 (t, want_rval, strict, now, fundef_p, > + flags)) > return true; > flags |= tf_error; > } > > tree target = NULL_TREE; > - return potential_constant_expression_1 (t, want_rval, strict, now, > + return potential_constant_expression_1 (t, want_rval, strict, now, fundef_p, > flags, &target); > } > > @@ -9886,7 +9952,9 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, > bool > potential_constant_expression (tree t) > { > - return potential_constant_expression_1 (t, false, true, false, tf_none); > + return potential_constant_expression_1 (t, /*want_rval*/false, /*strict*/true, > + /*now*/false, /*fundef_p*/false, > + tf_none); > } > > /* As above, but require a constant rvalue. */ > @@ -9894,7 +9962,9 @@ potential_constant_expression (tree t) > bool > potential_rvalue_constant_expression (tree t) > { > - return potential_constant_expression_1 (t, true, true, false, tf_none); > + return potential_constant_expression_1 (t, /*want_rval*/true, /*strict*/true, > + /*now*/false, /*fundef_p*/false, > + tf_none); > } > > /* Like above, but complain about non-constant expressions. */ > @@ -9902,7 +9972,8 @@ potential_rvalue_constant_expression (tree t) > bool > require_potential_constant_expression (tree t) > { > - return potential_constant_expression_1 (t, false, true, false, > + return potential_constant_expression_1 (t, /*want_rval*/false, /*strict*/true, > + /*now*/false, /*fundef_p*/false, > tf_warning_or_error); > } > > @@ -9911,7 +9982,18 @@ require_potential_constant_expression (tree t) > bool > require_potential_rvalue_constant_expression (tree t) > { > - return potential_constant_expression_1 (t, true, true, false, > + return potential_constant_expression_1 (t, /*want_rval*/true, /*strict*/true, > + /*now*/false, /*fundef_p*/false, > + tf_warning_or_error); > +} > + > +/* Like require_potential_rvalue_constant_expression, but fundef_p is true. */ > + > +bool > +require_potential_rvalue_constant_expression_fncheck (tree t) > +{ > + return potential_constant_expression_1 (t, /*want_rval*/true, /*strict*/true, > + /*now*/false, /*fundef_p*/true, > tf_warning_or_error); > } > > @@ -9920,7 +10002,8 @@ require_potential_rvalue_constant_expression (tree t) > bool > require_rvalue_constant_expression (tree t) > { > - return potential_constant_expression_1 (t, true, true, true, > + return potential_constant_expression_1 (t, /*want_rval*/true, /*strict*/true, > + /*now*/true, /*fundef_p*/false, > tf_warning_or_error); > } > > @@ -9934,7 +10017,9 @@ require_rvalue_constant_expression (tree t) > bool > is_constant_expression (tree t) > { > - return potential_constant_expression_1 (t, false, true, true, tf_none); > + return potential_constant_expression_1 (t, /*want_rval*/false, /*strict*/true, > + /*now*/true, /*fundef_p*/false, > + tf_none); > } > > /* As above, but expect an rvalue. */ > @@ -9942,7 +10027,9 @@ is_constant_expression (tree t) > bool > is_rvalue_constant_expression (tree t) > { > - return potential_constant_expression_1 (t, true, true, true, tf_none); > + return potential_constant_expression_1 (t, /*want_rval*/true, /*strict*/true, > + /*now*/true, /*fundef_p*/false, > + tf_none); > } > > /* Like above, but complain about non-constant expressions. */ > @@ -9950,7 +10037,8 @@ is_rvalue_constant_expression (tree t) > bool > require_constant_expression (tree t) > { > - return potential_constant_expression_1 (t, false, true, true, > + return potential_constant_expression_1 (t, /*want_rval*/false, /*strict*/true, > + /*now*/true, /*fundef_p*/false, > tf_warning_or_error); > } > > @@ -9960,7 +10048,9 @@ require_constant_expression (tree t) > bool > is_static_init_expression (tree t) > { > - return potential_constant_expression_1 (t, false, false, true, tf_none); > + return potential_constant_expression_1 (t, /*want_rval*/false, > + /*strict*/false, /*now*/true, > + /*fundef_p*/false, tf_none); > } > > /* Returns true if T is a potential constant expression that is not > diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h > index bbc8be21900..7a74132e4d0 100644 > --- a/gcc/cp/cp-tree.h > +++ b/gcc/cp/cp-tree.h > @@ -8452,6 +8452,7 @@ extern bool require_potential_constant_expression (tree); > extern bool require_constant_expression (tree); > extern bool require_rvalue_constant_expression (tree); > extern bool require_potential_rvalue_constant_expression (tree); > +extern bool require_potential_rvalue_constant_expression_fncheck (tree); > extern tree cxx_constant_value (tree, tree = NULL_TREE, > tsubst_flags_t = tf_error); > inline tree cxx_constant_value (tree t, tsubst_flags_t complain) > diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc > index c217d7e5aad..1e962b6e3b1 100644 > --- a/gcc/cp/method.cc > +++ b/gcc/cp/method.cc > @@ -1332,7 +1332,7 @@ struct comp_info > && !potential_rvalue_constant_expression (expr)) > { > if (was_constexp) > - require_potential_rvalue_constant_expression (expr); > + require_potential_rvalue_constant_expression_fncheck (expr); > else > constexp = false; > } > @@ -2670,13 +2670,17 @@ synthesized_method_walk (tree ctype, special_function_kind sfk, bool const_p, > requirements of a constexpr constructor (7.1.5), the > implicitly-defined default constructor is constexpr. > > + C++20: > The implicitly-defined copy/move assignment operator is constexpr if > - X is a literal type, and > - the assignment operator selected to copy/move each direct base class > subobject is a constexpr function, and > - for each non-static data member of X that is of class type (or array > thereof), the assignment operator selected to copy/move that > - member is a constexpr function. */ > + member is a constexpr function. > + > + C++23: > + The implicitly-defined copy/move assignment operator is constexpr. */ > if (constexpr_p) > *constexpr_p = (SFK_CTOR_P (sfk) > || (SFK_ASSIGN_P (sfk) && cxx_dialect >= cxx14) > diff --git a/gcc/doc/gcc/gcc-command-options/option-summary.rst b/gcc/doc/gcc/gcc-command-options/option-summary.rst > index d068f98feac..01123f55069 100644 > --- a/gcc/doc/gcc/gcc-command-options/option-summary.rst > +++ b/gcc/doc/gcc/gcc-command-options/option-summary.rst > @@ -89,7 +89,7 @@ in the following sections. > :option:`-Wno-deprecated-enum-enum-conversion` :option:`-Wno-deprecated-enum-float-conversion` |gol| > :option:`-Weffc++` :option:`-Wno-exceptions` :option:`-Wextra-semi` :option:`-Wno-inaccessible-base` |gol| > :option:`-Wno-inherited-variadic-ctor` :option:`-Wno-init-list-lifetime` |gol| > - :option:`-Winvalid-imported-macros` |gol| > + :option:`-Winvalid-constexpr` :option:`-Winvalid-imported-macros` |gol| > :option:`-Wno-invalid-offsetof` :option:`-Wno-literal-suffix` |gol| > :option:`-Wmismatched-new-delete` :option:`-Wmismatched-tags` |gol| > :option:`-Wmultiple-inheritance` :option:`-Wnamespaces` :option:`-Wnarrowing` |gol| > diff --git a/gcc/doc/gcc/gcc-command-options/options-controlling-c++-dialect.rst b/gcc/doc/gcc/gcc-command-options/options-controlling-c++-dialect.rst > index 5b05d31aae9..63517184c23 100644 > --- a/gcc/doc/gcc/gcc-command-options/options-controlling-c++-dialect.rst > +++ b/gcc/doc/gcc/gcc-command-options/options-controlling-c++-dialect.rst > @@ -989,6 +989,34 @@ In addition, these warning options have meanings only for C++ programs: > > Default setting; overrides :option:`-Wno-init-list-lifetime`. > > +.. option:: -Winvalid-constexpr > + > + .. note:: > + > + C++ and Objective-C++ only > + > + Warn when a function never produces a constant expression. In C++20 > + and earlier, for every ``constexpr`` function and function template, > + there must be at least one set of function arguments in at least one > + instantiation such that an invocation of the function or constructor > + could be an evaluated subexpression of a core constant expression. > + C++23 removed this restriction, so it's possible to have a function > + or a function template marked ``constexpr`` for which no invocation > + satisfies the requirements of a core constant expression. > + > + This warning is enabled as a pedantic warning by default in C++20 and > + earlier. In C++23, :option:`-Winvalid-constexpr` can be turned on, in > + which case it will be an ordinary warning. For example: > + > + .. code-block:: c++ > + > + void f (int& i); > + constexpr void > + g (int& i) > + { > + f(i); // warns by default in C++20, in C++23 only with -Winvalid-constexpr > + } > + > .. option:: -Winvalid-imported-macros > > Verify all imported macro definitions are valid at the end of > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ctor2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-ctor2.C > index 30b01091fd1..eabc586385f 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-ctor2.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ctor2.C > @@ -7,5 +7,5 @@ struct A > > struct B : A > { > - constexpr B(): A() { } // { dg-error "A::A" } > + constexpr B(): A() { } // { dg-error "A::A" "" { target c++20_down } } > }; > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-default-ctor.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-default-ctor.C > index 8d352d0bb99..2f9fbfb596a 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-default-ctor.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-default-ctor.C > @@ -7,6 +7,6 @@ struct A { > struct B: A { }; > constexpr int f(B b) { return b.i; } > > -struct C { C(); }; // { dg-message "" } > -struct D: C { }; // { dg-message "" } > -constexpr int g(D d) { return 42; } // { dg-error "invalid type" } > +struct C { C(); }; // { dg-message "" "" { target c++20_down } } > +struct D: C { }; // { dg-message "" "" { target c++20_down } } > +constexpr int g(D d) { return 42; } // { dg-error "invalid type" "" { target c++20_down } } > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-diag3.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-diag3.C > index c167bb1d8bc..5eedf42ba36 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-diag3.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-diag3.C > @@ -37,7 +37,7 @@ struct base // { dg-message "no .constexpr. constructor" "" { target { ! > > struct derived : public base // { dg-message "base class" "" { target { ! implicit_constexpr } } } > { > - constexpr derived(): base() { } // { dg-error "non-.constexpr. function" "" { target { ! implicit_constexpr } } } > + constexpr derived(): base() { } // { dg-error "non-.constexpr. function" "" { target { { ! implicit_constexpr } && c++20_down } } } > }; > > constexpr derived obj; // { dg-error "not literal" "" { target { ! implicit_constexpr } } } > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ex1.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-ex1.C > index 1d5c58b4090..5d11822acb5 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-ex1.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ex1.C > @@ -87,7 +87,7 @@ struct resource { > } > }; > constexpr resource f(resource d) > -{ return d; } // { dg-error "non-.constexpr." "" { target { ! implicit_constexpr } } } > +{ return d; } // { dg-error "non-.constexpr." "" { target { { ! implicit_constexpr } && c++20_down } } } > constexpr resource d = f(9); // { dg-message ".constexpr." "" { target { ! implicit_constexpr } } } > > // 4.4 floating-point constant expressions > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-friend.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-friend.C > index 85dfca4ff1d..3d171822855 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-friend.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-friend.C > @@ -5,7 +5,7 @@ struct A { A(); }; > > struct B { > friend constexpr int f(B) { return 0; } // OK > - friend constexpr int f(A) { return 0; } // { dg-error "constexpr" } > + friend constexpr int f(A) { return 0; } // { dg-error "constexpr" "" { target c++20_down } } > }; > > template > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-generated1.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-generated1.C > index 4b0d68bf661..98235719546 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-generated1.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-generated1.C > @@ -9,7 +9,7 @@ int g(); > > // We should complain about this. > template<> constexpr int A::f() > -{ return g(); } // { dg-error "non-.constexpr." } > +{ return g(); } // { dg-error "non-.constexpr." "" { target c++20_down } } > > // But not about this. > struct B > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ice5.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-ice5.C > index e934421c2f4..70327fc414a 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-ice5.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ice5.C > @@ -9,5 +9,5 @@ struct A > struct B > { > A a[1]; > - constexpr B() : a() {} // { dg-error "non-constant|non-.constexpr." "" { target { ! implicit_constexpr } } } > + constexpr B() : a() {} // { dg-error "non-constant|non-.constexpr." "" { target { { ! implicit_constexpr } && c++20_down } } } > }; > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ice6.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-ice6.C > index bf95b2443c7..7eabd333758 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-ice6.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ice6.C > @@ -6,6 +6,6 @@ struct A > A(int); > }; > > -struct B : A {}; // { dg-message "" } > +struct B : A {}; // { dg-message "" "" { target c++20_down } } > > -constexpr int foo(B) { return 0; } // { dg-error "invalid type" } > +constexpr int foo(B) { return 0; } // { dg-error "invalid type" "" { target c++20_down } } > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-memfn1.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-memfn1.C > index 37255282ded..0c95961c730 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-memfn1.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-memfn1.C > @@ -13,6 +13,6 @@ constexpr X X::g(X x) { return x; } > struct Y > { > Y() { } > - constexpr Y f(Y y) { return y; } // { dg-error "constexpr" "" { target { ! implicit_constexpr } } } > - static constexpr Y g(Y y) { return y; } // { dg-error "constexpr" "" { target { ! implicit_constexpr } } } > + constexpr Y f(Y y) { return y; } // { dg-error "constexpr" "" { target { { ! implicit_constexpr } && c++20_down } } } > + static constexpr Y g(Y y) { return y; } // { dg-error "constexpr" "" { target { { ! implicit_constexpr } && c++20_down } } } > }; > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-neg2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-neg2.C > index 793b4c3f5d3..4b27612d45c 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-neg2.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-neg2.C > @@ -15,13 +15,13 @@ constexpr int three = one() ? 3 : nonconst_func(0); > // such that the function invocation sub-stitution would produce a > // constant expression (5.19), the program is ill-formed; no diagnostic > // required. > -constexpr int bogus() { return zero () ? 3 : nonconst_func(0); } // { dg-error "nonconst_func" } > +constexpr int bogus() { return zero () ? 3 : nonconst_func(0); } // { dg-error "nonconst_func" "" { target c++20_down } } > > // Correctly rejected (not sure why). > -constexpr int correct_error() { return nonconst_func(0); } // { dg-error "nonconst_func" } > +constexpr int correct_error() { return nonconst_func(0); } // { dg-error "nonconst_func" "" { target c++20_down } } > > // Correctly rejected. > constexpr int z = bogus(); // { dg-error "" } > > // This is also correctly rejected. > -constexpr int correct_failure() { return 0 ? 3 : nonconst_func(0); } // { dg-error "nonconst_func" } > +constexpr int correct_failure() { return 0 ? 3 : nonconst_func(0); } // { dg-error "nonconst_func" "" { target c++20_down } } > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-non-const-arg.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-non-const-arg.C > index 0f68643f145..abbc70368d4 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-non-const-arg.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-non-const-arg.C > @@ -10,7 +10,7 @@ struct B { > int global; // { dg-message "not const" } > > struct D : B { > - constexpr D() : B(global) { } // { dg-error "global|argument" } > + constexpr D() : B(global) { } // { dg-error "global|argument" "" { target c++20_down } } > }; > > struct A2 { > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-reinterpret1.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-reinterpret1.C > index d7d244f752d..4e19cd36a9f 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/constexpr-reinterpret1.C > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-reinterpret1.C > @@ -17,7 +17,7 @@ public: > constexpr static Inner & getInner() > /* I am surprised this is considered a constexpr */ > { > - return *((Inner *)4); // { dg-error "reinterpret_cast" } > + return *((Inner *)4); // { dg-error "reinterpret_cast" "" { target c++20_down } } > } > }; > > diff --git a/gcc/testsuite/g++.dg/cpp0x/pr65327.C b/gcc/testsuite/g++.dg/cpp0x/pr65327.C > index e8149953ffd..b3ef57eec5f 100644 > --- a/gcc/testsuite/g++.dg/cpp0x/pr65327.C > +++ b/gcc/testsuite/g++.dg/cpp0x/pr65327.C > @@ -14,5 +14,5 @@ foo () > constexpr volatile int // { dg-warning "deprecated" "" { target c++2a } } > bar () > { > - return i; // { dg-error "lvalue-to-rvalue conversion of a volatile lvalue" } > + return i; // { dg-error "lvalue-to-rvalue conversion of a volatile lvalue" "" { target c++20_down } } > } > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-105050.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-105050.C > index e0688fbd38e..e5d53c9817b 100644 > --- a/gcc/testsuite/g++.dg/cpp1y/constexpr-105050.C > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-105050.C > @@ -5,7 +5,7 @@ void g(); > void h(); > > constexpr void f(int* p, int* q) { > - if (p != q && *p < 0) // { dg-error "neither branch of 'if' is a constant expression" } > + if (p != q && *p < 0) // { dg-error "neither branch of 'if' is a constant expression" "" { target c++20_down } } > g(); > else > h(); > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-89285-2.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-89285-2.C > index ea44daa849e..7b129fcee7a 100644 > --- a/gcc/testsuite/g++.dg/cpp1y/constexpr-89285-2.C > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-89285-2.C > @@ -10,7 +10,7 @@ struct B { > int *c = &x->a; > while (*c) > c = reinterpret_cast((reinterpret_cast(c) + *c)); > - *c = reinterpret_cast(this) - reinterpret_cast(c); // { dg-error "reinterpret_cast" } > + *c = reinterpret_cast(this) - reinterpret_cast(c); // { dg-error "reinterpret_cast" "" { target c++20_down } } > } > }; > struct C : A { > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-89285.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-89285.C > index 26aab9b6a50..fe0b8570ca2 100644 > --- a/gcc/testsuite/g++.dg/cpp1y/constexpr-89285.C > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-89285.C > @@ -10,7 +10,7 @@ struct B { > int *c = &x->a; > while (*c) > c = reinterpret_cast((reinterpret_cast(c) + *c)); > - *c = reinterpret_cast(this) - reinterpret_cast(c); // { dg-error "reinterpret_cast" } > + *c = reinterpret_cast(this) - reinterpret_cast(c); // { dg-error "reinterpret_cast" "" { target c++20_down } } > } > }; > struct C : A { > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-89785-2.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-89785-2.C > index 5cd46c791af..7afd9d24e98 100644 > --- a/gcc/testsuite/g++.dg/cpp1y/constexpr-89785-2.C > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-89785-2.C > @@ -11,7 +11,7 @@ foo (int x) > case 2: > break; > } > - throw 42; // { dg-error "is not a constant expression" } > + throw 42; // { dg-error "is not a constant expression" "" { target c++20_down } } > return 0; > } > > @@ -29,7 +29,7 @@ bar (int x) > continue; > break; > } > - throw -42; // { dg-error "is not a constant expression" } > + throw -42; // { dg-error "is not a constant expression" "" { target c++20_down } } > } > while (0); > return x; > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-local4.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-local4.C > index 647b5dcd7cd..180549e723a 100644 > --- a/gcc/testsuite/g++.dg/cpp1y/constexpr-local4.C > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-local4.C > @@ -10,7 +10,7 @@ const A a = 42; > > constexpr int f() > { > - const int j = a.i; // { dg-error "'a'" } > + const int j = a.i; // { dg-error "'a'" "" { target c++20_down } } > return j; > } > > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-neg1.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-neg1.C > index 8e9d1ea4943..53b5dd50f51 100644 > --- a/gcc/testsuite/g++.dg/cpp1y/constexpr-neg1.C > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-neg1.C > @@ -3,7 +3,7 @@ > struct A { A(); }; > > constexpr int f(int i) { > - static int j = i; // { dg-error "static" } > + static int j = i; // { dg-error "static" "" { target c++20_down } } > thread_local int l = i; // { dg-error "thread_local" "" { target c++20_down } } > goto foo; // { dg-error "goto" "" { target c++20_down } } > foo: > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-nsdmi7b.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-nsdmi7b.C > index ec10ddd2be8..a410e482664 100644 > --- a/gcc/testsuite/g++.dg/cpp1y/constexpr-nsdmi7b.C > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-nsdmi7b.C > @@ -21,7 +21,7 @@ bar() > A a = foo(); > a.p->n = 5; > return a; > -} // { dg-error "non-.constexpr." } > +} // { dg-error "non-.constexpr." "" { target c++20_down } } > > constexpr int > baz() > diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-throw.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-throw.C > index 3bbc8ac1b88..35928744686 100644 > --- a/gcc/testsuite/g++.dg/cpp1y/constexpr-throw.C > +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-throw.C > @@ -7,18 +7,18 @@ constexpr void f1() { > > constexpr void f2() { > if (true) > - throw; // { dg-error "not a constant expression" } > + throw; // { dg-error "not a constant expression" "" { target c++20_down } } > } > > constexpr void f3() { > if (false) > ; > else > - throw; // { dg-error "not a constant expression" } > + throw; // { dg-error "not a constant expression" "" { target c++20_down } } > } > > constexpr void f4() { > - throw; // { dg-error "not a constant expression" } > + throw; // { dg-error "not a constant expression" "" { target c++20_down } } > } > > constexpr int fun(int n) { > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit10.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit10.C > new file mode 100644 > index 00000000000..48706f7b66e > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit10.C > @@ -0,0 +1,96 @@ > +// PR c++/106649 > +// P2448 - Relaxing some constexpr restrictions > +// { dg-do compile { target c++23 } } > +// { dg-options "-Winvalid-constexpr -pedantic-errors" } > + > +// No constexpr constructors = not a literal type. > +struct NonLiteral { > + NonLiteral() {} > +}; > + > +// C++23: It is possible to write a constexpr function for which no > +// invocation satisfies the requirements of a core constant expression. > +constexpr NonLiteral > +fn0 (int) // { dg-warning "invalid return type" } > +{ > + return NonLiteral{}; > +} > + > +constexpr int > +fn1 (NonLiteral) // { dg-warning "invalid type" } > +{ > + return 42; > +} > + > +// From P2448. > +void f(int& i) { > + i = 0; > +} > + > +constexpr void g(int& i) { > + f(i); // { dg-warning "call to" } > +} > + > +// [dcl.constexpr] used to have this. > +constexpr int f(bool b) > + { return b ? throw 0 : 0; } // OK > +constexpr int f() { return f(true); } // ill-formed, no diagnostic required > + > +struct B { > + constexpr B(int) : i(0) { } > + int i; > +}; > + > +int global; > + > +struct D : B { > + constexpr D() : B(global) { } // { dg-warning "not usable" } > + // ill-formed, no diagnostic required > + // lvalue-to-rvalue conversion on non-constant global > +}; > + > +// If no specialization of the template would satisfy the requirements > +// for a constexpr function when considered as a non-template function, > +// the template is ill-formed, no diagnostic required. > +template > +constexpr void > +fn2 () > +{ > + int i = 42; > + f (i); > +} > + > +void > +fn3 () > +{ > + fn2(); > +} > + > +constexpr volatile int cvi = 10; > + > +constexpr int > +fn4 () > +{ > + return cvi; // { dg-warning "lvalue-to-rvalue conversion" } > +} > + > +constexpr unsigned int > +fn5 (int *p) > +{ > + unsigned int *q = reinterpret_cast(p); // { dg-warning "reinterpret_cast" } > + return *q; > +} > + > +constexpr int > +fn6 (int i) > +{ > + void *p = (void *) 1LL; // { dg-warning ".reinterpret_cast. from integer to pointer" } > + return 42; > +} > + > +constexpr int > +fn7 (int i) > +{ > + static int s = i; // { dg-warning "static" } > + return s; > +} > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit11.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit11.C > new file mode 100644 > index 00000000000..a7114bc66cb > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit11.C > @@ -0,0 +1,53 @@ > +// PR c++/106649 > +// P2448 - Relaxing some constexpr restrictions > +// { dg-do compile { target c++23 } } > +// { dg-options "-Winvalid-constexpr -pedantic-errors" } > + > +// [dcl.constexpr]/4 used to say: > +// The definition of a constexpr constructor whose function-body > +// is not = delete shall additionally satisfy the following requirements: > +// (4.1) for a non-delegating constructor, every constructor selected to initialize non-static data members and base class subobjects shall be a constexpr constructor; > +// (4.2) for a delegating constructor, the target constructor shall be a constexpr constructor. > + > +// This continues to be OK. > +struct Length { > + constexpr explicit Length(int i = 0) : val(i) { } > +private: > + int val; > +}; > + > +struct X { > + X() {} > + X(int i_) : i(i_) {} > + int i; > +}; > + > +struct S { > + X x; > + // Calls a non-constexpr constructor X::X(int). > + constexpr S(int i) : x(i) { } // { dg-warning "call to" } > + S(int, int) { } > + // Target constructor isn't constexpr. > + constexpr S() : S(42, 42) { } // { dg-warning "call to" } > +}; > + > +namespace N1 { > +struct X { > + void x(); > +}; > +struct Y { > + X x; > + constexpr void y() { x.x(); } // { dg-warning "call to" } > +}; > +} > + > +void g(); > + > +struct A { > + constexpr A() { g(); } // { dg-warning "call to" } > +}; > + > +struct B { > + constexpr B& operator=(const B&) { g(); return *this; } // { dg-warning "call to" } > + constexpr B& operator=(B&&) { g(); return *this; } // { dg-warning "call to" } > +}; > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit12.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit12.C > new file mode 100644 > index 00000000000..dd15e1552d7 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit12.C > @@ -0,0 +1,32 @@ > +// PR c++/106649 > +// P2448 - Relaxing some constexpr restrictions > +// { dg-do compile { target c++23 } } > +// Test that we get a diagnostic even in C++23 if you do call the function. > + > +constexpr unsigned int > +fn0 (const int *p) > +{ > + return *reinterpret_cast(p); // { dg-error ".reinterpret_cast. is not a constant expression" } > +} > + > +constexpr void * > +fn1 (int i) > +{ > + return (void *) 1LL; > +} > + > +void > +g () > +{ > + constexpr int i = 42; > + /* The diagnostics differ. fn0 is considered potentially-constant, but fn1 > + isn't due to "reinterpret_cast from integer to pointer". So for fn1, > + maybe_save_constexpr_fundef doesn't register_constexpr_fundef because > + 'potential' is false. Then cxx_eval_call_expression issues the "called > + in a constant expression" error, and explain_invalid_constexpr_fn doesn't > + explain what the problem is because it has "Only diagnose defaulted > + functions, lambdas, or instantiations." (With -Winvalid-constexpr, we > + emit more information.) */ > + constexpr auto a1 = fn0 (&i); > + constexpr auto a2 = fn1 (i); // { dg-error "called in a constant expression" } > +} > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit13.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit13.C > new file mode 100644 > index 00000000000..7997e8e2c3c > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit13.C > @@ -0,0 +1,14 @@ > +// PR c++/106649 > +// P2448 - Relaxing some constexpr restrictions > +// { dg-do compile { target c++23 } } > +// { dg-options "-Winvalid-constexpr" } > + > +constexpr volatile int i = 10; > + > +constexpr int > +bar () > +{ > + return i; // { dg-warning "lvalue-to-rvalue conversion of a volatile lvalue" } > +} > + > +constexpr int x = bar (); // { dg-error "called in a constant expression" } > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit14.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit14.C > new file mode 100644 > index 00000000000..f79ff15cbe2 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit14.C > @@ -0,0 +1,26 @@ > +// PR c++/106649 > +// P2448 - Relaxing some constexpr restrictions > +// { dg-do compile { target c++20 } } > +// { dg-options "" } > +// The definition of a constexpr destructor whose function-body is not > +// =delete shall additionally satisfy the following requirement: > +// (5.1) for every subobject of class type or (possibly multi-dimensional) > +// array thereof, that class type shall have a constexpr destructor. > + > +struct B { > + B() { } > + ~B() { } > +}; > + > +struct T : B { > + constexpr ~T() { } // { dg-warning "call to" "" { target c++20_down } } > +}; > + > +struct S { > + constexpr S() = default; // was error: implicit S() is not constexpr, now OK > + ~S() noexcept(false) = default; // OK, despite mismatched exception specification > +private: > + int i; > + S(S&); // OK: private copy constructor > +}; > +S::S(S&) = default; // OK: defines copy constructor > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit15.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit15.C > new file mode 100644 > index 00000000000..6441dabcc70 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit15.C > @@ -0,0 +1,43 @@ > +// PR c++/106649 > +// P2448 - Relaxing some constexpr restrictions > +// { dg-do compile { target c++23 } } > +// { dg-options "-Winvalid-constexpr" } > +// A copy/move assignment operator for a class X that is defaulted and > +// not defined as deleted is implicitly defined when it is odr-used, > +// when it is needed for constant evaluation, or when it is explicitly > +// defaulted after its first declaration. > +// The implicitly-defined copy/move assignment operator is constexpr. > + > +struct S { > + constexpr S() {} > + S& operator=(const S&) = default; // #1 > + S& operator=(S&&) = default; // #2 > +}; > + > +struct U { > + constexpr U& operator=(const U&) = default; > + constexpr U& operator=(U&&) = default; > +}; > + > +/* FIXME: If we only declare #1 and #2, and default them here: > + > + S& S::operator=(const S&) = default; > + S& S::operator=(S&&) = default; > + > +then they aren't constexpr. This sounds like a bug: > +. */ > + > +constexpr void > +g () > +{ > + S a; > + S b; > + b = a; > + b = S{}; > + > + U u, v; > + u = v; > + u = U{}; > +} > + > +static_assert ((g(), true), ""); > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit16.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit16.C > new file mode 100644 > index 00000000000..a6c4d19ffc6 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit16.C > @@ -0,0 +1,23 @@ > +// PR c++/106649 > +// P2448 - Relaxing some constexpr restrictions > +// { dg-do compile { target c++20 } } > +// { dg-options "" } > + > +template > +struct Wrapper { > + constexpr Wrapper() = default; > + constexpr Wrapper(Wrapper const&) = default; > + constexpr Wrapper(T const& t) : t(t) { } > + > + constexpr T get() const { return t; } > + constexpr bool operator==(Wrapper const&) const = default; // { dg-warning "call to" "" { target c++20_down } } > +private: > + T t; > +}; > + > +struct X { > + X(); > + bool operator==(X const&) const; > +}; > + > +Wrapper x; > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit3.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit3.C > index 3b5585dcd84..2238db91157 100644 > --- a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit3.C > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit3.C > @@ -5,6 +5,6 @@ constexpr int > foo () > { > goto lab; // { dg-error "'goto' in 'constexpr' function only available with" "" { target c++20_down } } > -lab: // { dg-error "'goto' is not a constant expression" "" { target { c++23 } } .-1 } > +lab: > return 1; > } > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit6.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit6.C > index fbeb83075b0..5a996cbc5c2 100644 > --- a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit6.C > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit6.C > @@ -5,7 +5,7 @@ > constexpr int > foo () > { > - goto lab; // { dg-error "'goto' is not a constant expression" } > + goto lab; // { dg-error "'goto' is not a constant expression" "" { target c++20_down } } > lab: > return 1; > } > @@ -13,13 +13,24 @@ lab: > constexpr int > bar () > { > - static int a; // { dg-error "'a' defined 'static' in 'constexpr' context" } > + static int a; // { dg-error "'a' defined 'static' in 'constexpr' context" "" { target c++20_down } } > return ++a; > } > > constexpr int > -baz (int x) > +baz () > { > - thread_local int a; // { dg-error "'a' defined 'thread_local' in 'constexpr' context" } > + thread_local int a; // { dg-error "'a' defined 'thread_local' in 'constexpr' context" "" { target c++20_down } } > return ++a; > } > + > +// In C++23, we get errors about the non-constant expressions only if we > +// actually call the functions in a constexpr context. > + > +void > +test () > +{ > + constexpr int a = foo (); // { dg-error "constant expression" } > + constexpr int b = bar (); // { dg-error "constant expression" } > + constexpr int c = baz (); // { dg-error "constant expression" } > +} > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit8.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit8.C > new file mode 100644 > index 00000000000..3fb1b93bd07 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit8.C > @@ -0,0 +1,96 @@ > +// PR c++/106649 > +// P2448 - Relaxing some constexpr restrictions > +// { dg-do compile { target c++14 } } > +// { dg-options "" } > + > +// No constexpr constructors = not a literal type. > +struct NonLiteral { > + NonLiteral() {} > +}; > + > +// C++23: It is possible to write a constexpr function for which no > +// invocation satisfies the requirements of a core constant expression. > +constexpr NonLiteral > +fn0 (int) // { dg-warning "invalid return type" "" { target c++20_down } } > +{ > + return NonLiteral{}; > +} > + > +constexpr int > +fn1 (NonLiteral) // { dg-warning "invalid type" "" { target c++20_down } } > +{ > + return 42; > +} > + > +// From P2448. > +void f(int& i) { > + i = 0; > +} > + > +constexpr void g(int& i) { > + f(i); // { dg-warning "call to" "" { target c++20_down } } > +} > + > +// [dcl.constexpr] used to have this. > +constexpr int f(bool b) > + { return b ? throw 0 : 0; } // OK > +constexpr int f() { return f(true); } // ill-formed, no diagnostic required > + > +struct B { > + constexpr B(int) : i(0) { } > + int i; > +}; > + > +int global; > + > +struct D : B { > + constexpr D() : B(global) { } // { dg-warning "not usable" "" { target c++20_down } } > + // ill-formed, no diagnostic required > + // lvalue-to-rvalue conversion on non-constant global > +}; > + > +// If no specialization of the template would satisfy the requirements > +// for a constexpr function when considered as a non-template function, > +// the template is ill-formed, no diagnostic required. > +template > +constexpr void > +fn2 () > +{ > + int i = 42; > + f (i); > +} > + > +void > +fn3 () > +{ > + fn2(); > +} > + > +constexpr volatile int cvi = 10; > + > +constexpr int > +fn4 () > +{ > + return cvi; // { dg-warning "lvalue-to-rvalue conversion" "" { target c++20_down } } > +} > + > +constexpr unsigned int > +fn5 (int *p) > +{ > + unsigned int *q = reinterpret_cast(p); // { dg-warning "reinterpret_cast" "" { target c++20_down } } > + return *q; > +} > + > +constexpr int > +fn6 (int i) > +{ > + void *p = (void *) 1LL; // { dg-warning ".reinterpret_cast. from integer to pointer" "" { target c++20_down } } > + return 42; > +} > + > +constexpr int > +fn7 (int i) > +{ > + static int s = i; // { dg-error "static" "" { target c++20_down } } > + return s; > +} > diff --git a/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit9.C b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit9.C > new file mode 100644 > index 00000000000..228e90f14c1 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp23/constexpr-nonlit9.C > @@ -0,0 +1,53 @@ > +// PR c++/106649 > +// P2448 - Relaxing some constexpr restrictions > +// { dg-do compile { target c++14 } } > +// { dg-options "" } > + > +// [dcl.constexpr]/4 used to say: > +// The definition of a constexpr constructor whose function-body > +// is not = delete shall additionally satisfy the following requirements: > +// (4.1) for a non-delegating constructor, every constructor selected to initialize non-static data members and base class subobjects shall be a constexpr constructor; > +// (4.2) for a delegating constructor, the target constructor shall be a constexpr constructor. > + > +// This continues to be OK. > +struct Length { > + constexpr explicit Length(int i = 0) : val(i) { } > +private: > + int val; > +}; > + > +struct X { > + X() {} > + X(int i_) : i(i_) {} > + int i; > +}; > + > +struct S { > + X x; > + // Calls a non-constexpr constructor X::X(int). > + constexpr S(int i) : x(i) { } // { dg-warning "call to" "" { target c++20_down } } > + S(int, int) { } > + // Target constructor isn't constexpr. > + constexpr S() : S(42, 42) { } // { dg-warning "call to" "" { target c++20_down } } > +}; > + > +namespace N1 { > +struct X { > + void x(); > +}; > +struct Y { > + X x; > + constexpr void y() { x.x(); } // { dg-warning "call to" "" { target c++20_down } } > +}; > +} > + > +void g(); > + > +struct A { > + constexpr A() { g(); } // { dg-warning "call to" "" { target c++20_down } } > +}; > + > +struct B { > + constexpr B& operator=(const B&) { g(); return *this; } // { dg-warning "call to" "" { target c++20_down } } > + constexpr B& operator=(B&&) { g(); return *this; } // { dg-warning "call to" "" { target c++20_down } } > +}; > diff --git a/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C b/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C > index efe97703a98..621c8dc21ea 100644 > --- a/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C > +++ b/gcc/testsuite/g++.dg/cpp23/feat-cxx2b.C > @@ -134,8 +134,8 @@ > > #ifndef __cpp_constexpr > # error "__cpp_constexpr" > -#elif __cpp_constexpr != 202110 > -# error "__cpp_constexpr != 202110" > +#elif __cpp_constexpr != 202207 > +# error "__cpp_constexpr != 202207" > #endif > > #ifndef __cpp_decltype_auto > diff --git a/gcc/testsuite/g++.dg/cpp2a/consteval3.C b/gcc/testsuite/g++.dg/cpp2a/consteval3.C > index 83463868668..627ab142d5a 100644 > --- a/gcc/testsuite/g++.dg/cpp2a/consteval3.C > +++ b/gcc/testsuite/g++.dg/cpp2a/consteval3.C > @@ -57,7 +57,6 @@ consteval int > f13 (int x) > { > static int a = 5; // { dg-error "'a' defined 'static' in 'consteval' function only available with" "" { target c++20_only } } > - // { dg-error "'a' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 } > thread_local int b = 6; // { dg-error "'b' defined 'thread_local' in 'consteval' function only available with" "" { target c++20_only } } > return x; > } > diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-new7.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-new7.C > index bb60a8ee91b..b2c98853882 100644 > --- a/gcc/testsuite/g++.dg/cpp2a/constexpr-new7.C > +++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-new7.C > @@ -13,7 +13,7 @@ void *operator new (std::size_t) noexcept; > constexpr bool > foo () > { > - auto p = static_cast (::operator new (sizeof (int))); // { dg-error "call to non-'constexpr' function" } > + auto p = static_cast (::operator new (sizeof (int))); // { dg-error "call to non-'constexpr' function" "" { target c++20_down } } > *p = 1; > ::operator delete (p); > return false; > @@ -24,7 +24,7 @@ struct S { constexpr S () : s (0) {} int s; }; > constexpr bool > bar () > { > - auto p = static_cast (::operator new (sizeof (S))); // { dg-error "call to non-'constexpr' function" } > + auto p = static_cast (::operator new (sizeof (S))); // { dg-error "call to non-'constexpr' function" "" { target c++20_down } } > auto q = new (p) S (); > q->s++; > q->~S (); > diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-try5.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-try5.C > index 216634dc56c..eb66105d7c4 100644 > --- a/gcc/testsuite/g++.dg/cpp2a/constexpr-try5.C > +++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-try5.C > @@ -6,7 +6,6 @@ constexpr int foo () > try { // { dg-warning "function-try-block body of 'constexpr' function only available with" "" { target c++17_down } } > int a; // { dg-error "uninitialized variable 'a' in 'constexpr' function" "" { target c++17_down } } > static double b = 1.0;// { dg-error "'b' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } } > - // { dg-error "'b' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 } > goto l; // { dg-error "'goto' in 'constexpr' function only available with" "" { target c++20_down } } > l:; > return 0; > @@ -22,7 +21,6 @@ constexpr int bar () > { > int a; // { dg-error "uninitialized variable 'a' in 'constexpr' function" "" { target c++17_down } } > static long double b = 3.0;// { dg-error "'b' defined 'static' in 'constexpr' function only available with" "" { target c++20_down } } > - // { dg-error "'b' defined 'static' in 'constexpr' context" "" { target c++23 } .-1 } > goto l; // { dg-error "'goto' in 'constexpr' function only available with" "" { target c++20_down } } > l:; > try { // { dg-warning "'try' in 'constexpr' function only available with" "" { target c++17_down } } > diff --git a/gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr1.C b/gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr1.C > index dff59271a1e..fb62ecbfdb5 100644 > --- a/gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr1.C > +++ b/gcc/testsuite/g++.dg/cpp2a/spaceship-constexpr1.C > @@ -9,7 +9,7 @@ struct A > struct B > { > A a; > - bool operator==(const B&) const = default; // { dg-error "A::operator==" "" { target { ! implicit_constexpr } } } > + bool operator==(const B&) const = default; // { dg-error "A::operator==" "" { target { { ! implicit_constexpr } && c++20_down } } } > }; > > constexpr bool x = B() == B(); // { dg-error "non-.constexpr" "" { target { ! implicit_constexpr } } } > diff --git a/gcc/testsuite/g++.dg/cpp2a/spaceship-eq3.C b/gcc/testsuite/g++.dg/cpp2a/spaceship-eq3.C > index 7a517a8016c..69eaa7b9b20 100644 > --- a/gcc/testsuite/g++.dg/cpp2a/spaceship-eq3.C > +++ b/gcc/testsuite/g++.dg/cpp2a/spaceship-eq3.C > @@ -7,8 +7,8 @@ struct A { > struct D > { > A i; > - bool operator==(const D& x) const = default; // { dg-error "A::operator==" } > - bool operator!=(const D& z) const = default; // { dg-error "D::operator==" } > + bool operator==(const D& x) const = default; // { dg-error "A::operator==" "" { target c++20_down } } > + bool operator!=(const D& z) const = default; // { dg-error "D::operator==" "" { target c++20_down } } > }; > > constexpr D d{A()}; > diff --git a/gcc/testsuite/g++.dg/diagnostic/constexpr1.C b/gcc/testsuite/g++.dg/diagnostic/constexpr1.C > index c962a60c847..19242d15ba8 100644 > --- a/gcc/testsuite/g++.dg/diagnostic/constexpr1.C > +++ b/gcc/testsuite/g++.dg/diagnostic/constexpr1.C > @@ -1,7 +1,5 @@ > // { dg-do compile { target c++11 } } > > constexpr int foo() { thread_local int i __attribute__((unused)) {}; return 1; } // { dg-error "40:.i. defined .thread_local." "" { target c++20_down } } > -// { dg-error "40:.i. defined .thread_local. in .constexpr. context" "" { target c++23 } .-1 } > > constexpr int bar() { static int i __attribute__((unused)) {}; return 1; } // { dg-error "34:.i. defined .static." "" { target c++20_down } } > -// { dg-error "34:.i. defined .static. in .constexpr. context" "" { target c++23 } .-1 } > diff --git a/gcc/testsuite/g++.dg/gomp/pr79664.C b/gcc/testsuite/g++.dg/gomp/pr79664.C > index 582eedb6d6d..f4c30c0b3f4 100644 > --- a/gcc/testsuite/g++.dg/gomp/pr79664.C > +++ b/gcc/testsuite/g++.dg/gomp/pr79664.C > @@ -1,6 +1,6 @@ > // PR c++/79664 > // { dg-do compile } > -// { dg-options "-std=c++14 -fopenmp" } > +// { dg-options "-std=c++14 -fopenmp -Winvalid-constexpr -pedantic-errors" } > > constexpr int > f1 () > diff --git a/gcc/testsuite/g++.dg/ubsan/vptr-4.C b/gcc/testsuite/g++.dg/ubsan/vptr-4.C > index a21d3d60a3a..1efd3f77a55 100644 > --- a/gcc/testsuite/g++.dg/ubsan/vptr-4.C > +++ b/gcc/testsuite/g++.dg/ubsan/vptr-4.C > @@ -1,7 +1,7 @@ > // Verify that -fsanitize=vptr downcast instrumentation works properly > // inside of constexpr. > // { dg-do compile } > -// { dg-options "-std=c++11 -fsanitize=vptr" } > +// { dg-options "-std=c++11 -fsanitize=vptr -Winvalid-constexpr -pedantic-errors" } > > struct S { > constexpr S() : a(0) {} > > base-commit: e505f7493bed1395d121d2f53137ec11706fa42e