From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 821F0385AC1D; Thu, 17 Feb 2022 19:57:08 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 821F0385AC1D From: "qinzhao at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/102276] -ftrivial-auto-var-init fails to initialize a variable, causes a spurious warning Date: Thu, 17 Feb 2022 19:57:08 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: middle-end X-Bugzilla-Version: 12.0 X-Bugzilla-Keywords: diagnostic X-Bugzilla-Severity: normal X-Bugzilla-Who: qinzhao at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: qinzhao at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: 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: Thu, 17 Feb 2022 19:57:08 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102276 --- Comment #14 from qinzhao at gcc dot gnu.org --- (In reply to Jakub Jelinek from comment #7) > and so for flag_auto_var_init > AUTO_INIT_UNINITIALIZED perhaps we could = also > avoid warnings on: > 1) call to .DEFERRED_INIT > 2) call to __builtin_clear_padding if the second argument is present and > non-zero > 3) I guess we would need not to warn on a gimple assign store right after > the .DEFERRED_INIT call that has the lhs of .DEFERRED_INIT as rhs > anything else? After more study of the source code for maybe_warn_switch_unreachable, I realize that in order to emit the switch_unreachable warning, "warn_switch_unreachable_r" first is called to scan the switch sequence and saved the FIRST "REAL" gimple stmt. then it will check this FIRST "REAL" s= tmt to see whether it's the LABEL, if it's not, then report the switch unreacha= ble warning.=20 So, we only need to consider the FIRST "REAL" gimple for the above 3 cases.= For all the 3 cases, the FIRST "REAL" gimple is a call to .DEFERRED_INIT.=20 So, inside maybe_warn_switch_unreachable, we only need to check whether the FIRST gimple is a cal .DEFERRED_INIT, that's enough.=