From patchwork Mon Feb 21 08:25:03 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jakub Jelinek X-Patchwork-Id: 1595391 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=Uyit9gbf; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org (client-ip=2620:52:3:1:0:246e:9693:128c; helo=sourceware.org; envelope-from=gcc-patches-bounces+incoming=patchwork.ozlabs.org@gcc.gnu.org; receiver=) Received: from sourceware.org (server2.sourceware.org [IPv6:2620:52:3:1:0:246e:9693:128c]) (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 4K2Fk52wVXz9sFh for ; Mon, 21 Feb 2022 19:25:49 +1100 (AEDT) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id D351D3857C4F for ; Mon, 21 Feb 2022 08:25:46 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org D351D3857C4F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1645431946; bh=mkNkoNZ+RtU02RVhQKneQh5vP8zXFxYXyIxrdTIAgKw=; h=Date:To:Subject:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=Uyit9gbf0HaMR6J+I6lGfL55jqaq0/W1GkrYHLvq3J9weTQYWEpTGC2qy6j6pwpwc Ws1+n81lqK8NTndz+g514RcBZcCGT6+oPp62L8aGFruG6KDBfKMFu2jzqwBox1B/IY L35WWcLezA/HNfMnLBiWgyz5dr7mq+gKoj7FhRJU= X-Original-To: gcc-patches@gcc.gnu.org Delivered-To: gcc-patches@gcc.gnu.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 700263858C78 for ; Mon, 21 Feb 2022 08:25:25 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 700263858C78 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-595-exeT-pekNFeAp6BvY0umrg-1; Mon, 21 Feb 2022 03:25:20 -0500 X-MC-Unique: exeT-pekNFeAp6BvY0umrg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6B06F1006AA4 for ; Mon, 21 Feb 2022 08:25:19 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.125]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 020F862D6E; Mon, 21 Feb 2022 08:25:06 +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 21L8P3FE933512 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Mon, 21 Feb 2022 09:25:04 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.16.1/8.16.1/Submit) id 21L8P31K933511; Mon, 21 Feb 2022 09:25:03 +0100 Date: Mon, 21 Feb 2022 09:25:03 +0100 To: Jason Merrill Subject: [PATCH] c++: Fix up constexpr evaluation of new with zero sized types [PR104568] Message-ID: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-Spam-Status: No, score=-5.1 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, 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" Hi! The new expression constant expression evaluation right now tries to deduce how many elts the array it uses for the heap or heap [] vars should have (or how many elts should its trailing array have if it has cookie at the start). As new is lowered at that point to (some_type *) ::operator new (size) or so, it computes it by subtracting cookie size if any from size, then divides the result by sizeof (some_type). This works fine for most types, except when sizeof (some_type) is 0, then we divide by zero; size is then equal to cookie_size (or if there is no cookie, to 0). The following patch special cases those cases so that we don't divide by zero and also recover the original outer_nelts from the expression by forcing the size not to be folded in that case but be explicit 0 * outer_nelts or cookie_size + 0 * outer_nelts. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? Note, we have further issues, we accept-invalid various cases, for both zero sized elt_type and even non-zero sized elts, we aren't able to diagnose out of bounds POINTER_PLUS_EXPR like: constexpr bool foo () { auto p = new int[2]; auto q1 = &p[0]; auto q2 = &p[1]; auto q3 = &p[2]; auto q4 = &p[3]; delete[] p; return true; } constexpr bool a = foo (); That doesn't look like a regression so I think we should resolve that for GCC 13, but there are 2 problems. Figure out why cxx_fold_pointer_plus_expression doesn't deal with the &heap [] etc. cases, and for the zero sized arrays, I think we really need to preserve whether user wrote an array ref or pointer addition, because in the &p[3] case if sizeof(p[0]) == 0 we know that if it has 2 elements it is out of bounds, while if we see p p+ 0 the information if it was p + 2 or p + 3 in the source is lost. clang++ seems to handle it fine even in the zero sized cases or with new expressions. 2022-02-21 Jakub Jelinek PR c++/104568 * cp-tree.h (build_new_constexpr_heap_type): Add FULL_SIZE_ADJUSTED argument. * init.cc (build_new_constexpr_heap_type): Add FULL_SIZE_ADJUSTED argument. If true, don't subtract csz from it nor divide by int_size_in_bytes (elt_type). Don't do that division if int_size_in_bytes is zero either. (maybe_wrap_new_for_constexpr): Pass false to build_new_constexpr_heap_type. (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 (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 var_size to build_new_constexpr_heap_type together with true for the last argument. * g++.dg/cpp2a/constexpr-new22.C: New test. Jakub --- gcc/cp/cp-tree.h.jj 2022-02-09 20:13:51.541304861 +0100 +++ gcc/cp/cp-tree.h 2022-02-17 15:34:30.804453673 +0100 @@ -7038,7 +7038,7 @@ extern tree build_offset_ref (tree, tr extern tree throw_bad_array_new_length (void); extern bool type_has_new_extended_alignment (tree); extern unsigned malloc_alignment (void); -extern tree build_new_constexpr_heap_type (tree, tree, tree); +extern tree build_new_constexpr_heap_type (tree, tree, tree, bool); extern tree build_new (location_t, vec **, tree, tree, vec **, --- gcc/cp/init.cc.jj 2022-02-05 10:50:05.000000000 +0100 +++ gcc/cp/init.cc 2022-02-17 15:56:30.010056499 +0100 @@ -2930,7 +2930,8 @@ std_placement_new_fn_p (tree alloc_fn) it is computed such that the size of the struct fits into FULL_SIZE. */ 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 full_size, + bool full_size_adjusted) { gcc_assert (cookie_size == NULL_TREE || tree_fits_uhwi_p (cookie_size)); gcc_assert (full_size == NULL_TREE || tree_fits_uhwi_p (full_size)); @@ -2939,9 +2940,14 @@ build_new_constexpr_heap_type (tree elt_ 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); + unsigned HOST_WIDE_INT esz = int_size_in_bytes (elt_type); + if (!full_size_adjusted) + { + gcc_assert (fsz >= csz); + fsz -= csz; + if (esz) + fsz /= esz; + } itype2 = build_index_type (size_int (fsz - 1)); if (!cookie_size) return build_cplus_array_type (elt_type, itype2); @@ -2992,7 +2998,7 @@ maybe_wrap_new_for_constexpr (tree alloc return alloc_call; tree rtype = build_new_constexpr_heap_type (elt_type, cookie_size, - NULL_TREE); + NULL_TREE, false); return build_nop (build_pointer_type (rtype), alloc_call); } @@ -3398,6 +3404,12 @@ 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, @@ -3474,7 +3486,7 @@ 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/cp/constexpr.cc.jj 2022-02-17 10:24:16.779112954 +0100 +++ gcc/cp/constexpr.cc 2022-02-17 15:43:23.399026306 +0100 @@ -7253,6 +7253,7 @@ 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; + bool var_size_adjusted = false; if (TREE_CODE (elt_type) == RECORD_TYPE && TYPE_NAME (elt_type) == heap_identifier) { @@ -7264,9 +7265,66 @@ 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))) + { + tree arg0 = CALL_EXPR_ARG (oldop, 0); + STRIP_NOPS (arg0); + if (cookie_size) + { + if (TREE_CODE (arg0) != PLUS_EXPR) + arg0 = NULL_TREE; + else if (TREE_CODE (TREE_OPERAND (arg0, 0)) + == INTEGER_CST + && tree_int_cst_equal (cookie_size, + TREE_OPERAND (arg0, + 0))) + { + arg0 = TREE_OPERAND (arg0, 1); + STRIP_NOPS (arg0); + } + else if (TREE_CODE (TREE_OPERAND (arg0, 1)) + == INTEGER_CST + && tree_int_cst_equal (cookie_size, + TREE_OPERAND (arg0, + 1))) + { + arg0 = TREE_OPERAND (arg0, 0); + STRIP_NOPS (arg0); + } + else + arg0 = NULL_TREE; + } + if (arg0 && TREE_CODE (arg0) == MULT_EXPR) + { + tree op0 = TREE_OPERAND (arg0, 0); + tree op1 = TREE_OPERAND (arg0, 1); + var_size_adjusted = true; + if (integer_zerop (op0)) + var_size + = cxx_eval_constant_expression (ctx, op1, false, + non_constant_p, + overflow_p); + else if (integer_zerop (op1)) + var_size + = cxx_eval_constant_expression (ctx, op0, false, + non_constant_p, + overflow_p); + else + var_size_adjusted = false; + } + } TREE_TYPE (var) = build_new_constexpr_heap_type (elt_type, cookie_size, - var_size); + var_size, var_size_adjusted); TREE_TYPE (TREE_OPERAND (op, 0)) = build_pointer_type (TREE_TYPE (var)); } --- gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C.jj 2022-02-17 16:01:24.804945381 +0100 +++ gcc/testsuite/g++.dg/cpp2a/constexpr-new22.C 2022-02-17 16:00:55.720350985 +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 ();