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Fri, 18 Mar 2022 14:55:41 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy2zRzzkJZs4LAqPc2rhQIBO4ibourfwUuKrqxT1W4Puxu0tGHofadS2v6CIlBIRX9q57xdFg== X-Received: by 2002:a05:622a:107:b0:2e1:d655:cc4c with SMTP id u7-20020a05622a010700b002e1d655cc4cmr9113466qtw.669.1647640541073; Fri, 18 Mar 2022 14:55:41 -0700 (PDT) Received: from redhat.com ([2601:184:4780:4310::5f2c]) by smtp.gmail.com with ESMTPSA id p13-20020a05622a048d00b002e1ce0c627csm6790603qtx.58.2022.03.18.14.55.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Mar 2022 14:55:40 -0700 (PDT) Date: Fri, 18 Mar 2022 17:55:38 -0400 To: Jason Merrill Subject: [PATCH v2] c++: ICE with template code in constexpr [PR104284] Message-ID: References: <20220310220459.91301-1-polacek@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.1.5 (2021-12-30) X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-Spam-Status: No, score=-13.9 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Marek Polacek via Gcc-patches From: Marek Polacek Reply-To: Marek Polacek Cc: GCC Patches Errors-To: gcc-patches-bounces+incoming=patchwork.ozlabs.org@gcc.gnu.org Sender: "Gcc-patches" On Fri, Mar 11, 2022 at 06:46:42PM -0500, Jason Merrill wrote: > On 3/10/22 18:04, Marek Polacek wrote: > > Since r9-6073 cxx_eval_store_expression preevaluates the value to > > be stored, and that revealed a crash where a template code (here, > > code=IMPLICIT_CONV_EXPR) leaks into cxx_eval*. > > > > It happens because we're performing build_vec_init while processing > > a template > > Hmm, that seems like the bug. Where's that call coming from? From build_aggr_init. So we're handling e.g. template constexpr void g () { constexpr S s2[]{{'a'}}; } cp_finish_decl (decl=s2, init={{'a'}}) sees we're in processing_template_decl, but also that we have a constexpr var which is not dependent, nor is its initializer: else if (init && (init_const_expr_p || DECL_DECLARED_CONSTEXPR_P (decl)) && !TYPE_REF_P (type) && decl_maybe_constant_var_p (decl) && !(dep_init = value_dependent_init_p (init))) { /* This variable seems to be a non-dependent constant, so process its initializer. If check_initializer returns non-null the initialization wasn't constant after all. */ tree init_code; cleanups = make_tree_vector (); init_code = check_initializer (decl, init, flags, &cleanups); so we call check_initializer, where we go down this path: init_code = build_aggr_init_full_exprs (decl, init, flags); build_aggr_init sees that the type of 's2' is ARRAY_TYPE, so it calls build_vec_init. I now recall that we've discussed build_vec_init in a template in the past, for example in the context of c++/93676. So I agree we ought to make an effort to avoid calling build_vec_init in a template. Perhaps like this: use an INIT_EXPR. With that, we should call build_vec_init if needed while instantiating. Does that make any sense? Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? -- >8 -- Since r9-6073 cxx_eval_store_expression preevaluates the value to be stored, and that revealed a crash where a template code (here, code=IMPLICIT_CONV_EXPR) leaks into cxx_eval*. It happens because we're performing build_vec_init while processing a template, which calls get_temp_regvar which creates an INIT_EXPR. This INIT_EXPR's RHS contains an rvalue conversion so we create an IMPLICIT_CONV_EXPR. Its operand is not type-dependent and the whole INIT_EXPR is not type-dependent. So we call build_non_dependent_expr which, with -fchecking=2, calls fold_non_dependent_expr. At this point the expression still has an IMPLICIT_CONV_EXPR, which ought to be handled in instantiate_non_dependent_expr_internal. However, tsubst_copy_and_build doesn't handle INIT_EXPR; it will just call tsubst_copy which does nothing when args is null. So we fail to replace the IMPLICIT_CONV_EXPR and ICE. The problem is that we call build_vec_init in a template in the first place. It should work to create an INIT_EXPR in a template and only perform build_vec_init when instantiating. PR c++/104284 gcc/cp/ChangeLog: * init.cc (build_aggr_init): Don't call build_vec_init in a template, create an INIT_EXPR instead. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-104284-1.C: New test. * g++.dg/cpp1y/constexpr-104284-2.C: New test. * g++.dg/cpp1y/constexpr-104284-3.C: New test. * g++.dg/cpp1y/constexpr-104284-4.C: New test. --- gcc/cp/init.cc | 11 +++--- .../g++.dg/cpp1y/constexpr-104284-1.C | 34 ++++++++++++++++++ .../g++.dg/cpp1y/constexpr-104284-2.C | 33 +++++++++++++++++ .../g++.dg/cpp1y/constexpr-104284-3.C | 33 +++++++++++++++++ .../g++.dg/cpp1y/constexpr-104284-4.C | 35 +++++++++++++++++++ 5 files changed, 142 insertions(+), 4 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C base-commit: 0c016888ffd569c4b70722cf7df2efcc003f397b diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc index 7575597c8fd..58e66adbfe1 100644 --- a/gcc/cp/init.cc +++ b/gcc/cp/init.cc @@ -2006,10 +2006,13 @@ build_aggr_init (tree exp, tree init, int flags, tsubst_flags_t complain) } } - stmt_expr = build_vec_init (exp, NULL_TREE, init, - /*explicit_value_init_p=*/false, - from_array, - complain); + /* build_vec_init is not meant to be used in templates. */ + if (processing_template_decl) + stmt_expr = build2 (INIT_EXPR, itype, exp, init); + else + stmt_expr = build_vec_init (exp, NULL_TREE, init, + /*explicit_value_init_p=*/false, + from_array, complain); TREE_READONLY (exp) = was_const; TREE_THIS_VOLATILE (exp) = was_volatile; TREE_TYPE (exp) = type; diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C new file mode 100644 index 00000000000..809c26a6161 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-1.C @@ -0,0 +1,34 @@ +// PR c++/104284 +// { dg-do compile { target c++14 } } +// { dg-additional-options "-fchecking=2" } + +struct S { + char c{}; +}; + +auto x1 = [](auto) { constexpr S s[]{{}}; }; +auto x2 = [](auto) { constexpr S s[]{{'a'}}; }; +#if __cpp_designated_initializers >= 201707L +auto x3 = [](auto) { constexpr S s[]{{.c = 'a'}}; }; +#endif +auto x4 = [](auto) { constexpr S s[]{'a'}; }; +auto x5 = [](auto) { constexpr S s[]{{{}}}; }; + +template +constexpr void g () +{ + constexpr S s1[]{{}}; + static_assert(s1[0].c == '\0', ""); + constexpr S s2[]{{'a'}}; + static_assert(s2[0].c == 'a', ""); +#if __cpp_designated_initializers >= 201707L + constexpr S s3[]{{.c = 'a'}}; + static_assert(s3[0].c == 'a', ""); +#endif + constexpr S s4[]{'a'}; + static_assert(s4[0].c == 'a', ""); + constexpr S s5[]{{{}}}; + static_assert(s5[0].c == '\0', ""); +} + +static_assert ((g(), true), ""); diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C new file mode 100644 index 00000000000..704d37de129 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-2.C @@ -0,0 +1,33 @@ +// PR c++/104284 +// { dg-do compile { target c++14 } } +// { dg-additional-options "-fchecking=2" } + +struct S { + char a; + constexpr S() : a{'a'} { } + constexpr S(char a_) : a{a_} { } +}; + +auto x1 = [](auto) { constexpr S s[]{{}}; }; +auto x2 = [](auto) { constexpr S s[]{{'a'}}; }; +auto x3 = [](auto) { constexpr S s[]{'a'}; }; +auto x4 = [](auto) { constexpr S s[]{{{}}}; }; + +template +constexpr void g() +{ + constexpr S s1[]{{}}; + static_assert(s1[0].a == 'a', ""); + constexpr S s2[]{{'a'}}; + static_assert(s2[0].a == 'a', ""); + constexpr S s3[]{'a'}; + static_assert(s3[0].a == 'a', ""); + constexpr S s4[]{{{}}}; + static_assert(s4[0].a == '\0', ""); +} + +void +f () +{ + g(); +} diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C new file mode 100644 index 00000000000..6f23b255f9c --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-3.C @@ -0,0 +1,33 @@ +// PR c++/104284 +// { dg-do compile { target c++14 } } +// { dg-additional-options "-fchecking=2" } +// Like constexpr-104284.C, but the function template is not +// constexpr. In that case, we were still calling build_vec_init +// in a template, just not crashing. + +struct S { + char c{}; +}; + +template +void g () +{ + constexpr S s1[]{{}}; + static_assert(s1[0].c == '\0', ""); + constexpr S s2[]{{'a'}}; + static_assert(s2[0].c == 'a', ""); +#if __cpp_designated_initializers >= 201707L + constexpr S s3[]{{.c = 'a'}}; + static_assert(s3[0].c == 'a', ""); +#endif + constexpr S s4[]{'a'}; + static_assert(s4[0].c == 'a', ""); + constexpr S s5[]{{{}}}; + static_assert(s5[0].c == '\0', ""); +} + +void +f () +{ + g(); +} diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C new file mode 100644 index 00000000000..a99d3255a47 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284-4.C @@ -0,0 +1,35 @@ +// PR c++/104284 +// { dg-do run { target c++14 } } +// { dg-additional-options "-fchecking=2" } + +struct S { + char c{}; +}; + +template +constexpr void g () +{ + S s1[]{{}}; + if (s1[0].c != '\0') + __builtin_abort (); + S s2[]{{'a'}}; + if (s2[0].c != 'a') + __builtin_abort (); +#if __cpp_designated_initializers >= 201707L + S s3[]{{.c = 'a'}}; + if (s3[0].c != 'a') + __builtin_abort (); +#endif + S s4[]{'a'}; + if (s4[0].c != 'a') + __builtin_abort (); + S s5[]{{{}}}; + if (s5[0].c != '\0') + __builtin_abort (); +} + +int +main () +{ + g(); +}