From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 79C8F396E81D; Wed, 2 Sep 2020 07:44:37 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 79C8F396E81D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1599032677; bh=faqS2LopgmgDjIJwBfXKXSKA4cPjujXOnweHzk1s3PY=; h=From:To:Subject:Date:From; b=UkMzwK8F3fcDGv0qrRp89gzMmdeev0RTwwDWgxfYo6H44/g8lO5Ru87grbeG6wj4U qW515NJZ2JhcHVf5L1TxsFae0b7YwhrYqb3H38NOttE56AWe8jtTzViv/YziFgodHN BlVbSJEmMHR08mpWmYJhEM6hSDjy6YmGR65AFGBM= From: "vries at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug analyzer/96894] New: Analyzer assumes pointer is NULL, even if pointer was tested to be non-null before Date: Wed, 02 Sep 2020 07:44:37 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: analyzer X-Bugzilla-Version: 11.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: vries at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: dmalcolm at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter target_milestone attachments.created Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: gcc-bugs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-bugs mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 02 Sep 2020 07:44:37 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96894 Bug ID: 96894 Summary: Analyzer assumes pointer is NULL, even if pointer was tested to be non-null before Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: analyzer Assignee: dmalcolm at gcc dot gnu.org Reporter: vries at gcc dot gnu.org Target Milestone: --- Created attachment 49174 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D49174&action=3Dedit fibheap.c, preprocessed version from gdb/binutils master Using gcc-11 (SUSE Linux) 11.0.0 20200901 (experimental) [revision b1850c617b14eedaf60b358f3b7d4707cff73b8a]. Invoked like this: ... $ gcc-11 fibheap.c -fanalyzer -S ... We have: ... fibheap.c: In function =E2=80=98fibnode_remove=E2=80=99: fibheap.c:3122:42: warning: dereference of NULL =E2=80=98*(node).parent=E2= =80=99 [CWE-690] [-Wanalyzer-null-dereference] 3122 | && node->parent->child =3D=3D node) | ~~~~~~~~~~~~^~~~~~~ ... Looking at the source code, we have: ... 3118 if (node->parent !=3D 3119 3120 ((void *)0) 3121 3122 && node->parent->child =3D=3D node) 3123 node->parent->child =3D ret; ... So, just before dereferencing node->parent, we check that it's non-null, so= the warning that node->parent is dereferenced while it's null makes no sense.=