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Fri, 01 Mar 2024 02:55:45 -0500 X-MC-Unique: xSPvegesPXKH7pM0zcXRNA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0B0D31C0782D for ; Fri, 1 Mar 2024 07:55:45 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.45.226.25]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C4C721BDB1; Fri, 1 Mar 2024 07:55:44 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.17.1/8.17.1) with ESMTPS id 4217th6u506007 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 1 Mar 2024 08:55:43 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.17.1/8.17.1/Submit) id 4217th1V506006; Fri, 1 Mar 2024 08:55:43 +0100 Date: Fri, 1 Mar 2024 08:55:43 +0100 From: Jakub Jelinek To: Jason Merrill Cc: gcc-patches@gcc.gnu.org Subject: [PATCH] c++, v2: Fix up decltype of non-dependent structured binding decl in template [PR92687] Message-ID: Reply-To: Jakub Jelinek References: MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Spam-Status: No, score=-3.7 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,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=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Thu, Feb 29, 2024 at 12:50:47PM +0100, Jakub Jelinek wrote: > finish_decltype_type uses DECL_HAS_VALUE_EXPR_P (expr) check for > DECL_DECOMPOSITION_P (expr) to determine if it is > array/struct/vector/complex etc. subobject proxy case vs. structured > binding using std::tuple_{size,element}. > For non-templates or when templates are already instantiated, that works > correctly, finalized DECL_DECOMPOSITION_P non-base vars indeed have > DECL_VALUE_EXPR in the former case and don't have it in the latter. > It works fine for dependent structured bindings as well, cp_finish_decomp in > that case creates DECLTYPE_TYPE tree and defers the handling until > instantiation. > As the testcase shows, this doesn't work for the non-dependent structured > binding case in templates, because DECL_HAS_VALUE_EXPR_P is set in that case > always; cp_finish_decomp ends with: > if (processing_template_decl) > { > for (unsigned int i = 0; i < count; i++) > if (!DECL_HAS_VALUE_EXPR_P (v[i])) > { > tree a = build_nt (ARRAY_REF, decl, size_int (i), > NULL_TREE, NULL_TREE); > SET_DECL_VALUE_EXPR (v[i], a); > DECL_HAS_VALUE_EXPR_P (v[i]) = 1; > } > } > and those artificial ARRAY_REFs are used in various places during > instantiation to find out what base the DECL_DECOMPOSITION_P VAR_DECLs > have and their positions. > Another option would be to change > tree > lookup_decomp_type (tree v) > { > - return *decomp_type_table->get (v); > + if (tree *slot = decomp_type_table->get (v)) > + return *slot; > + return NULL_TREE; > } > > and in finish_decl_decomp either just in the ptds.saved case or always > try to lookup_decomp_type, if it returns non-NULL, return what it returned, > otherwise return unlowered_expr_type (expr). I guess it would be cleaner, > I thought it would be more costly due to the hash table lookup, but now that > I think about it again, DECL_VALUE_EXPR is a hash table lookup as well. > So maybe then > + if (ptds.saved) > + { > + gcc_checking_assert (DECL_HAS_VALUE_EXPR_P (expr)); > + /* DECL_HAS_VALUE_EXPR_P is always set if > + processing_template_decl. If lookup_decomp_type > + returns non-NULL, it is the tuple case. */ > + if (tree ret = lookup_decomp_type (expr)) > + return ret; > + } > if (DECL_HAS_VALUE_EXPR_P (expr)) > /* Expr is an array or struct subobject proxy, handle > bit-fields properly. */ > return unlowered_expr_type (expr); > else > /* Expr is a reference variable for the tuple case. */ > return lookup_decomp_type (expr); Here is a variant of the patch which does that. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? Or the other version, or adding some flag to the DECL_DECOMPOSITION_P decls? 2024-03-01 Jakub Jelinek PR c++/92687 * decl.cc (lookup_decomp_type): Return NULL_TREE if decomp_type_table doesn't have entry for V. * semantics.cc (finish_decltype_type): If ptds.saved, assert DECL_HAS_VALUE_EXPR_P is true and decide on tuple vs. non-tuple based on if lookup_decomp_type is NULL or not. * g++.dg/cpp1z/decomp59.C: New test. --- gcc/cp/decl.cc.jj 2024-02-28 23:20:01.004751204 +0100 +++ gcc/cp/decl.cc 2024-02-29 20:03:11.087218176 +0100 @@ -9262,7 +9262,9 @@ static GTY((cache)) decl_tree_cache_map tree lookup_decomp_type (tree v) { - return *decomp_type_table->get (v); + if (tree *slot = decomp_type_table->get (v)) + return *slot; + return NULL_TREE; } /* Mangle a decomposition declaration if needed. Arguments like --- gcc/cp/semantics.cc.jj 2024-02-28 22:57:08.101800588 +0100 +++ gcc/cp/semantics.cc 2024-02-29 20:04:51.936880622 +0100 @@ -11804,6 +11804,15 @@ finish_decltype_type (tree expr, bool id access expression). */ if (DECL_DECOMPOSITION_P (expr)) { + if (ptds.saved) + { + gcc_checking_assert (DECL_HAS_VALUE_EXPR_P (expr)); + /* DECL_HAS_VALUE_EXPR_P is always set if + processing_template_decl. If lookup_decomp_type + returns non-NULL, it is the tuple case. */ + if (tree ret = lookup_decomp_type (expr)) + return ret; + } if (DECL_HAS_VALUE_EXPR_P (expr)) /* Expr is an array or struct subobject proxy, handle bit-fields properly. */ --- gcc/testsuite/g++.dg/cpp1z/decomp59.C.jj 2024-02-29 20:02:17.467929327 +0100 +++ gcc/testsuite/g++.dg/cpp1z/decomp59.C 2024-02-29 20:02:17.467929327 +0100 @@ -0,0 +1,63 @@ +// PR c++/92687 +// { dg-do compile { target c++11 } } +// { dg-options "" } + +namespace std { + template struct tuple_size; + template struct tuple_element; +} + +struct A { + int i; + template int& get() { return i; } +}; + +template<> struct std::tuple_size { static const int value = 2; }; +template struct std::tuple_element { using type = int; }; + +template +struct is_reference { + static const bool value = false; +}; + +template +struct is_reference +{ + static const bool value = true; +}; + +template +struct is_reference +{ + static const bool value = true; +}; + +template +void +foo () +{ + auto [x, y] = A {}; // { dg-warning "structured bindings only available with" "" { target c++14_down } } + static_assert (!is_reference::value, ""); +} + +void +bar () +{ + auto [x, y] = A {}; // { dg-warning "structured bindings only available with" "" { target c++14_down } } + static_assert (!is_reference::value, ""); +} + +template +void +baz () +{ + auto [x, y] = T {}; // { dg-warning "structured bindings only available with" "" { target c++14_down } } + static_assert (!is_reference::value, ""); +} + +void +qux () +{ + foo<0> (); + baz (); +} Jakub