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[69.118.112.187]) by smtp.gmail.com with ESMTPSA id da35-20020a05620a362300b007853b0cd29csm585517qkb.1.2024.01.31.09.12.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 31 Jan 2024 09:12:57 -0800 (PST) From: Patrick Palka To: gcc-patches@gcc.gnu.org Cc: jason@redhat.com, Patrick Palka Subject: [PATCH] c++: ttp CTAD equivalence [PR112737] Date: Wed, 31 Jan 2024 12:12:45 -0500 Message-ID: <20240131171245.1102131-1-ppalka@redhat.com> X-Mailer: git-send-email 2.43.0.493.gbc7ee2e5e1 MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-13.5 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_H5, RCVD_IN_MSPIKE_WL, RCVD_IN_SORBS_WEB, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk? -- >8 -- Here during declaration matching we undesirably consider the two TT{42} CTAD expressions to be non-equivalent ultimately because for CTAD placeholder equivalence we compare the TEMPLATE_DECLs (which uses pointer identity) and here the corresponding TEMPLATE_DECLs for TT are different since they're from different scopes. On the other hand, the corresponding TEMPLATE_TEMPLATE_PARMs are deemed equivalent (since they have the same position and template parameters). This turns out to be the root cause of some of the xtreme-header modules regressions. We don't have this ttp equivalence issue in other contexts because either the TEMPLATE_TEMPLATE_PARM is used instead of the TEMPLATE_DECL already (e.g. when a ttp is used as a targ), or the equivalence logic is relaxed (e.g. for bound ttps), it seems. So this patch relaxes ttp CTAD placeholder equivalence accordingly, by comparing the TEMPLATE_TEMPLATE_PARM instead of the TEMPLATE_DECL. The ctp_hasher doesn't need to be adjusted since it currently doesn't include CLASS_PLACEHOLDER_TEMPLATE in the hash anyway. PR c++/112737 gcc/cp/ChangeLog: * typeck.cc (structural_comptypes) : If CLASS_PLACEHOLDER_TEMPLATE is a ttp, compare its TEMPLATE_TEMPLATE_PARM instead of its TEMPLATE_DECL. gcc/testsuite/ChangeLog: * g++.dg/template/ttp42: New test. --- gcc/cp/typeck.cc | 20 +++++++++++++++++--- gcc/testsuite/g++.dg/template/ttp42.C | 14 ++++++++++++++ 2 files changed, 31 insertions(+), 3 deletions(-) create mode 100644 gcc/testsuite/g++.dg/template/ttp42.C diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc index a15eda3f5f8..be82877e35c 100644 --- a/gcc/cp/typeck.cc +++ b/gcc/cp/typeck.cc @@ -1573,9 +1573,23 @@ structural_comptypes (tree t1, tree t2, int strict) return false; /* If T1 and T2 don't represent the same class template deduction, they aren't equal. */ - if (CLASS_PLACEHOLDER_TEMPLATE (t1) - != CLASS_PLACEHOLDER_TEMPLATE (t2)) - return false; + if (CLASS_PLACEHOLDER_TEMPLATE (t1) || CLASS_PLACEHOLDER_TEMPLATE (t2)) + { + tree tmpl1 = CLASS_PLACEHOLDER_TEMPLATE (t1); + tree tmpl2 = CLASS_PLACEHOLDER_TEMPLATE (t2); + if (!tmpl1 || !tmpl2) + return false; + if (DECL_TEMPLATE_TEMPLATE_PARM_P (tmpl1) + != DECL_TEMPLATE_TEMPLATE_PARM_P (tmpl2)) + return false; + if (DECL_TEMPLATE_TEMPLATE_PARM_P (tmpl1) + /* Treat two CTAD placeholders that use equivalent ttps + from different scopes as equivalent by comparing their + TEMPLATE_TEMPLATE_PARMs instead of their TEMPLATE_DECLs. */ + ? !same_type_p (TREE_TYPE (tmpl1), TREE_TYPE (tmpl2)) + : tmpl1 != tmpl2) + return false; + } /* Constrained 'auto's are distinct from parms that don't have the same constraints. */ if (!equivalent_placeholder_constraints (t1, t2)) diff --git a/gcc/testsuite/g++.dg/template/ttp42.C b/gcc/testsuite/g++.dg/template/ttp42.C new file mode 100644 index 00000000000..da08e857fc5 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/ttp42.C @@ -0,0 +1,14 @@ +// PR c++/112737 +// { dg-do compile { target c++17 } } + +template class TT> +decltype(TT{42}) f(); // #1 + +template class TT> +decltype(TT{42}) f(); // redeclaration of #1 + +template struct A { A(T); }; + +int main() { + f(); +}