From patchwork Wed Mar 16 16:55:18 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jakub Jelinek X-Patchwork-Id: 1606258 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=gcc.gnu.org header.i=@gcc.gnu.org header.a=rsa-sha256 header.s=default header.b=Eg0uENvw; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org (client-ip=8.43.85.97; helo=sourceware.org; envelope-from=gcc-patches-bounces+incoming=patchwork.ozlabs.org@gcc.gnu.org; receiver=) Received: from sourceware.org (ip-8-43-85-97.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4KJc07060gz9s8s for ; 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Wed, 16 Mar 2022 12:55:22 -0400 X-MC-Unique: rPSunkhcNayJePWXcwpbPg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A18C83C19850 for ; Wed, 16 Mar 2022 16:55:22 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.81]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 55B2D2156893; Wed, 16 Mar 2022 16:55:22 +0000 (UTC) Received: from tucnak.zalov.cz (localhost [127.0.0.1]) by tucnak.zalov.cz (8.16.1/8.16.1) with ESMTPS id 22GGtJm52505356 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Wed, 16 Mar 2022 17:55:19 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.16.1/8.16.1/Submit) id 22GGtIME2505355; Wed, 16 Mar 2022 17:55:18 +0100 Date: Wed, 16 Mar 2022 17:55:18 +0100 To: Jason Merrill Subject: [PATCH] c++, v2: Fix up constexpr evaluation of new with zero sized types [PR104568] Message-ID: References: <5d0d1a93-c4af-b728-913a-5f70a6d9faed@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-Spam-Status: No, score=-4.8 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_H5, 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: Jakub Jelinek via Gcc-patches From: Jakub Jelinek Reply-To: Jakub Jelinek Cc: gcc-patches@gcc.gnu.org Errors-To: gcc-patches-bounces+incoming=patchwork.ozlabs.org@gcc.gnu.org Sender: "Gcc-patches" On Tue, Mar 15, 2022 at 04:19:05PM -0400, Jason Merrill wrote: > > But if you strongly prefer it that way, I can do that. > > Note, probably not 3 new args but 4, depends on whether we could turn > > all those cases where the tree arg0 = CALL_EXPR_ARG (oldop, 0); > > is done but var_size_adjusted is false into assertion failures. > > I'm worried that with the zero size of element we could end up with > > a variable number of elements which when multiplied by 0 gives constant 0, > > though hopefully that would be rejected earlier during constant evaluation. > > Or we could move all the adjustment into a separate function and only ever > pass the number of elements to build_new_constexpr_heap_type? So like this? 2022-03-16 Jakub Jelinek PR c++/104568 * init.cc (build_new_constexpr_heap_type): Remove FULL_SIZE argument and its handling, instead add ITYPE2 argument. Only support COOKIE_SIZE != NULL. (build_new_1): If size is 0, change it to 0 * outer_nelts if outer_nelts is non-NULL. Pass type rather than elt_type to maybe_wrap_new_for_constexpr. * constexpr.cc (build_new_constexpr_heap_type): New function. (cxx_eval_constant_expression) : If elt_size is zero sized type, try to recover outer_nelts from the size argument to operator new/new[] and pass that as arg_size to build_new_constexpr_heap_type. Pass ctx, non_constant_p and overflow_p to that call too. * g++.dg/cpp2a/constexpr-new22.C: New test. Jakub --- gcc/cp/constexpr.cc.jj 2022-03-16 15:25:26.294551244 +0100 +++ gcc/cp/constexpr.cc 2022-03-16 17:27:08.202184961 +0100 @@ -6422,6 +6422,84 @@ maybe_warn_about_constant_value (locatio } } +/* For element type ELT_TYPE, return the appropriate type of the heap object + containing such element(s). COOKIE_SIZE is NULL or the size of cookie + in bytes. If COOKIE_SIZE is NULL, return array type + ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return + struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; } + where N is is computed such that the size of the struct fits into FULL_SIZE. + If ARG_SIZE is non-NULL, it is the first argument to the new operator. + It should be passed if ELT_TYPE is zero sized type in which case FULL_SIZE + will be also 0 and so it is not possible to determine the actual array + size. CTX, NON_CONSTANT_P and OVERFLOW_P are used during constant + expression evaluation of subexpressions of ARG_SIZE. */ + +tree +build_new_constexpr_heap_type (const constexpr_ctx *ctx, tree elt_type, + tree cookie_size, tree full_size, tree arg_size, + bool *non_constant_p, bool *overflow_p) +{ + gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size)); + gcc_assert (tree_fits_uhwi_p (full_size)); + unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0; + if (arg_size) + { + STRIP_NOPS (arg_size); + if (cookie_size) + { + if (TREE_CODE (arg_size) != PLUS_EXPR) + arg_size = NULL_TREE; + else if (TREE_CODE (TREE_OPERAND (arg_size, 0)) == INTEGER_CST + && tree_int_cst_equal (cookie_size, + TREE_OPERAND (arg_size, 0))) + { + arg_size = TREE_OPERAND (arg_size, 1); + STRIP_NOPS (arg_size); + } + else if (TREE_CODE (TREE_OPERAND (arg_size, 1)) == INTEGER_CST + && tree_int_cst_equal (cookie_size, + TREE_OPERAND (arg_size, 1))) + { + arg_size = TREE_OPERAND (arg_size, 0); + STRIP_NOPS (arg_size); + } + else + arg_size = NULL_TREE; + } + if (arg_size && TREE_CODE (arg_size) == MULT_EXPR) + { + tree op0 = TREE_OPERAND (arg_size, 0); + tree op1 = TREE_OPERAND (arg_size, 1); + if (integer_zerop (op0)) + arg_size + = cxx_eval_constant_expression (ctx, op1, false, non_constant_p, + overflow_p); + else if (integer_zerop (op1)) + arg_size + = cxx_eval_constant_expression (ctx, op0, false, non_constant_p, + overflow_p); + else + arg_size = NULL_TREE; + } + else + arg_size = NULL_TREE; + } + + unsigned HOST_WIDE_INT fsz = tree_to_uhwi (arg_size ? arg_size : full_size); + unsigned HOST_WIDE_INT esz = int_size_in_bytes (elt_type); + if (!arg_size) + { + gcc_assert (fsz >= csz); + fsz -= csz; + if (esz) + fsz /= esz; + } + tree itype2 = build_index_type (size_int (fsz - 1)); + if (!cookie_size) + return build_cplus_array_type (elt_type, itype2); + return build_new_constexpr_heap_type (elt_type, cookie_size, itype2); +} + /* Attempt to reduce the expression T to a constant value. On failure, issue diagnostic and return error_mark_node. */ /* FIXME unify with c_fully_fold */ @@ -7253,6 +7331,7 @@ cxx_eval_constant_expression (const cons tree var_size = TYPE_SIZE_UNIT (TREE_TYPE (var)); tree elt_type = TREE_TYPE (type); tree cookie_size = NULL_TREE; + tree arg_size = NULL_TREE; if (TREE_CODE (elt_type) == RECORD_TYPE && TYPE_NAME (elt_type) == heap_identifier) { @@ -7264,9 +7343,21 @@ cxx_eval_constant_expression (const cons DECL_NAME (var) = (DECL_NAME (var) == heap_uninit_identifier ? heap_identifier : heap_vec_identifier); + /* For zero sized elt_type, try to recover how many outer_nelts + it should have. */ + if ((cookie_size ? tree_int_cst_equal (var_size, cookie_size) + : integer_zerop (var_size)) + && !int_size_in_bytes (elt_type) + && TREE_CODE (oldop) == CALL_EXPR + && call_expr_nargs (oldop) >= 1) + if (tree fun = get_function_named_in_call (oldop)) + if (cxx_replaceable_global_alloc_fn (fun) + && IDENTIFIER_NEW_OP_P (DECL_NAME (fun))) + arg_size = CALL_EXPR_ARG (oldop, 0); TREE_TYPE (var) - = build_new_constexpr_heap_type (elt_type, cookie_size, - var_size); + = build_new_constexpr_heap_type (ctx, elt_type, cookie_size, + var_size, arg_size, + non_constant_p, overflow_p); TREE_TYPE (TREE_OPERAND (op, 0)) = build_pointer_type (TREE_TYPE (var)); } --- gcc/cp/init.cc.jj 2022-03-16 15:25:26.431549398 +0100 +++ gcc/cp/init.cc 2022-03-16 17:23:03.922500101 +0100 @@ -2931,33 +2931,17 @@ std_placement_new_fn_p (tree alloc_fn) } /* For element type ELT_TYPE, return the appropriate type of the heap object - containing such element(s). COOKIE_SIZE is NULL or the size of cookie - in bytes. FULL_SIZE is NULL if it is unknown how big the heap allocation - will be, otherwise size of the heap object. If COOKIE_SIZE is NULL, - return array type ELT_TYPE[FULL_SIZE / sizeof(ELT_TYPE)], otherwise return + containing such element(s). COOKIE_SIZE is the size of cookie in bytes. + Return struct { size_t[COOKIE_SIZE/sizeof(size_t)]; ELT_TYPE[N]; } - where N is nothing (flexible array member) if FULL_SIZE is NULL, otherwise - it is computed such that the size of the struct fits into FULL_SIZE. */ + where N is nothing (flexible array member) if ITYPE2 is NULL, otherwise + the array has ITYPE2 as its TYPE_DOMAIN. */ tree -build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree full_size) +build_new_constexpr_heap_type (tree elt_type, tree cookie_size, tree itype2) { - gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size)); - gcc_assert (full_size == NULL_TREE || tree_fits_uhwi_p (full_size)); - unsigned HOST_WIDE_INT csz = cookie_size ? tree_to_uhwi (cookie_size) : 0; - tree itype2 = NULL_TREE; - if (full_size) - { - unsigned HOST_WIDE_INT fsz = tree_to_uhwi (full_size); - gcc_assert (fsz >= csz); - fsz -= csz; - fsz /= int_size_in_bytes (elt_type); - itype2 = build_index_type (size_int (fsz - 1)); - if (!cookie_size) - return build_cplus_array_type (elt_type, itype2); - } - else - gcc_assert (cookie_size); + gcc_assert (tree_fits_uhwi_p (cookie_size)); + unsigned HOST_WIDE_INT csz = tree_to_uhwi (cookie_size); csz /= int_size_in_bytes (sizetype); tree itype1 = build_index_type (size_int (csz - 1)); tree atype1 = build_cplus_array_type (sizetype, itype1); @@ -3408,6 +3392,12 @@ build_new_1 (vec **placemen outer_nelts_check = NULL_TREE; } + /* If size is zero e.g. due to type having zero size, try to + preserve outer_nelts for constant expression evaluation + purposes. */ + if (integer_zerop (size) && outer_nelts) + size = build2 (MULT_EXPR, TREE_TYPE (size), size, outer_nelts); + alloc_call = build_operator_new_call (fnname, placement, &size, &cookie_size, align_arg, outer_nelts_check, @@ -3484,7 +3474,7 @@ build_new_1 (vec **placemen } if (cookie_size) - alloc_call = maybe_wrap_new_for_constexpr (alloc_call, elt_type, + alloc_call = maybe_wrap_new_for_constexpr (alloc_call, type, cookie_size); /* In the simple case, we can stop now. */ --- gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C.jj 2022-03-16 16:45:04.011372629 +0100 +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C 2022-03-16 16:45:04.011372629 +0100 @@ -0,0 +1,42 @@ +// PR c++/104568 +// { dg-do compile { target c++20 } } +// { dg-options "" } + +struct S { int s; constexpr S () : s (0) {} constexpr ~S () {} }; +typedef int T[0]; +typedef int U[0]; + +constexpr bool +foo () +{ + auto p = new T[2]; + auto q1 = &p[0]; + auto q2 = &p[1]; + auto q3 = &p[2]; + delete[] p; + return true; +} + +constexpr bool +bar () +{ + auto p = new U[2]; + auto q1 = &p[0]; + auto q2 = &p[1]; + auto q3 = &p[2]; + delete[] p; + return true; +} + +constexpr bool +baz () +{ + auto p = new T[0]; + auto q1 = &p[0]; + delete[] p; + return true; +} + +constexpr bool a = foo (); +constexpr bool b = bar (); +constexpr bool c = baz ();