From patchwork Tue Mar 1 18:41:54 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jakub Jelinek X-Patchwork-Id: 51488 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 756FA3858C2C for ; Tue, 1 Mar 2022 18:42:32 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 756FA3858C2C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1646160152; bh=dhfxtNNhsvDijiEJ/E8O9LG2gXLj8kLu7fL2LzC9Odo=; h=Date:To:Subject:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=AgrD7w9lfkQy58oC4UETVNbkK21eLEtYoZAW+/5sw3gbUJrkb1h01EPkblPj3xDsT 0cAZknCIX6RjdRSWbAeoiULUboxtXADZWMtlVILH4gpS5xZflirU4wRaZKrHsJMK8b XJLhxU6jTo3u5NPLJulkEOwF32OlcRubwPCz4QL8= 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 4DCF63858D20 for ; Tue, 1 Mar 2022 18:42:03 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 4DCF63858D20 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-659--uqX4VInOyK3nxN70_cCwQ-1; Tue, 01 Mar 2022 13:41:59 -0500 X-MC-Unique: -uqX4VInOyK3nxN70_cCwQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 83E861006AA5; Tue, 1 Mar 2022 18:41:58 +0000 (UTC) Received: from tucnak.zalov.cz (unknown [10.39.192.57]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0142A804F1; Tue, 1 Mar 2022 18:41:57 +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 221Ift5P3311406 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 1 Mar 2022 19:41:55 +0100 Received: (from jakub@localhost) by tucnak.zalov.cz (8.16.1/8.16.1/Submit) id 221IfsIl3311405; Tue, 1 Mar 2022 19:41:54 +0100 Date: Tue, 1 Mar 2022 19:41:54 +0100 To: Richard Biener , Jeff Law Subject: [PATCH] warn-access: Fix up check_pointer_uses [PR104715] Message-ID: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-Spam-Status: No, score=-5.3 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, 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, Martin Sebor Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" Hi! The following testcase emits bogus -Wdangling-pointer warnings. The bug is that when it sees that ptr immediate use is a call that returns one of its arguments, it will assume that the return value is based on ptr, but that is the case only if ptr is passed to the argument that is actually returned (so e.g. for memcpy the first argument, etc.). When the builtins guarantee e.g. that the result is based on the first argument (either ERF_RETURNS_ARG 0 in which case it will always just returns the first argument as is, or when it is something like strstr or strpbrk or mempcpy that it returns some pointer based on the first argument), it means the result is not based on second or following argument if any. The second hunk fixes this. The first hunk just removes an unnecessary TREE_CODE check, the code only pushes SSA_NAMEs into the pointers vector and if it didn't, it uses FOR_EACH_IMM_USE_FAST (use_p, iter, ptr) a few lines below this, which of course requires that ptr is a SSA_NAME. Tree checking on SSA_NAME_VERSION will already ensure that if it wasn't a SSA_NAME, we'd ICE. Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2022-03-01 Jakub Jelinek PR tree-optimization/104715 * gimple-ssa-warn-access.cc (pass_waccess::check_pointer_uses): Don't unnecessarily test if ptr is a SSA_NAME, it has to be. Only push lhs of a call if gimple_call_return_arg is equal to ptr, not just when it is non-NULL. * c-c++-common/Wdangling-pointer-7.c: New test. Jakub --- gcc/gimple-ssa-warn-access.cc.jj 2022-02-28 16:22:40.860520930 +0100 +++ gcc/gimple-ssa-warn-access.cc 2022-02-28 16:55:01.242272499 +0100 @@ -4169,8 +4169,7 @@ pass_waccess::check_pointer_uses (gimple for (unsigned i = 0; i != pointers.length (); ++i) { tree ptr = pointers[i]; - if (TREE_CODE (ptr) == SSA_NAME - && !bitmap_set_bit (visited, SSA_NAME_VERSION (ptr))) + if (!bitmap_set_bit (visited, SSA_NAME_VERSION (ptr))) /* Avoid revisiting the same pointer. */ continue; @@ -4267,7 +4266,7 @@ pass_waccess::check_pointer_uses (gimple if (gcall *call = dyn_cast (use_stmt)) { - if (gimple_call_return_arg (call)) + if (gimple_call_return_arg (call) == ptr) if (tree lhs = gimple_call_lhs (call)) if (TREE_CODE (lhs) == SSA_NAME) pointers.safe_push (lhs); --- gcc/testsuite/c-c++-common/Wdangling-pointer-7.c.jj 2022-02-28 17:09:09.906355082 +0100 +++ gcc/testsuite/c-c++-common/Wdangling-pointer-7.c 2022-02-28 17:03:50.533839892 +0100 @@ -0,0 +1,36 @@ +/* PR tree-optimization/104715 */ +/* { dg-do compile } */ +/* { dg-options "-Wdangling-pointer" } */ + +char * +foo (char *p) +{ + { + char q[61] = "012345678901234567890123456789012345678901234567890123456789"; + char *r = q; + p = __builtin_strcat (p, r); + } + return p; /* { dg-bogus "using dangling pointer" } */ +} + +char * +bar (char *p) +{ + { + char q[] = "0123456789"; + char *r = q; + p = __builtin_strstr (p, r); + } + return p; /* { dg-bogus "using dangling pointer" } */ +} + +char * +baz (char *p) +{ + { + char q[] = "0123456789"; + char *r = q; + p = __builtin_strpbrk (p, r); + } + return p; /* { dg-bogus "using dangling pointer" } */ +}