From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 110123857BA8; Fri, 17 Nov 2023 14:51:12 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 110123857BA8 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1700232672; bh=p3ySBshJO81C7rpsaxO0KlD3Qz369wbOTJJXtMyEvn4=; h=From:To:Subject:Date:In-Reply-To:References:From; b=aY6xK2FTCX3DXUd78F1uFIBSaN2wZrommMuC3FxBBoMUUQpG5S3KoQMQgpmYqGkiA qngvuNP1GEP24sdSJjsUAYa34Zoz1CZrV0KPAx9xK8W/OEyO9ULV3Uo9efz1BXtkQU GaexgOhPk3GsOzYnNUFgAN/y5uE77k4LHXrrUcTA= From: "cvs-commit at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/107571] Missing fallthrough attribute diagnostics Date: Fri, 17 Nov 2023 14:51:10 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Version: 13.0 X-Bugzilla-Keywords: diagnostic X-Bugzilla-Severity: normal X-Bugzilla-Who: cvs-commit at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned 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 List-Id: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107571 --- Comment #4 from CVS Commits --- The master branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:52eedfa00960f2d255ec542626e3531a65aa8bb8 commit r14-5561-g52eedfa00960f2d255ec542626e3531a65aa8bb8 Author: Jakub Jelinek Date: Fri Nov 17 15:43:31 2023 +0100 c++: Implement C++ DR 2406 - [[fallthrough]] attribute and iteration statements The following patch implements CWG 2406 - [[fallthrough]] attribute and iteration statements The genericization of some loops leaves nothing at all or just a label after a body of a loop, so if the loop is later followed by case or default label in a switch, the fallthrough statement isn't diagnosed. The following patch implements it by marking the IFN_FALLTHROUGH call in such a case, such that during gimplification it can be pedantically diagnosed even if it is followed by case or default label or some normal labels followed by case/default labels. While looking into this, I've discovered other problems. expand_FALLTHROUGH_r is removing the IFN_FALLTHROUGH calls from the IL, but wasn't telling that to walk_gimple_stmt/walk_gimple_seq_mod, so the callers would then skip the next statement after it, and it would return non-NULL if the removed stmt was last in the sequence. This cou= ld lead to wi->callback_result being set even if it didn't appear at the v= ery end of switch sequence. The patch makes use of wi->removed_stmt such that the callers properly know what happened, and use different way to handle the end of switch sequence case. That change discovered a bug in the gimple-walk handling of wi->removed_stmt. If that flag is set, the callback is telling the cal= lers that the current statement has been removed and so the innermost walk_gimple_seq_mod shouldn't gsi_next. The problem is that wi->removed_stmt is only reset at the start of a walk_gimple_stmt, but = that can be too late for some cases. If we have two nested gimple sequences, say GIMPLE_BIND as the last stmt of some gimple seq, we remove the last statement inside of that GIMPLE_BIND, set wi->removed_stmt there, don't do gsi_next correctly because already gsi_remove moved us to the next s= tmt, there is no next stmt, so we return back to the caller, but wi->removed_stmt is still set and so we don't do gsi_next even in the outer sequence, despite the GIMPLE_BIND (etc.) not being removed. That means we walk the GIMPLE_BIND with its whole sequence again. The patch fixes that by resetting wi->removed_stmt after we've used that flag in walk_gimple_seq_mod. Nothing really uses that flag after the outermost walk_gimple_seq_mod, it is just a private notification that the stmt callback has removed a stmt. 2023-11-17 Jakub Jelinek PR c++/107571 gcc/ * gimplify.cc (expand_FALLTHROUGH_r): Use wi->removed_stmt after gsi_remove, change the way of passing fallthrough stmt at the e= nd of sequence to expand_FALLTHROUGH. Diagnose IFN_FALLTHROUGH with GF_CALL_NOTHROW flag. (expand_FALLTHROUGH): Change loc into array of 2 location_t elt= s, don't test wi.callback_result, instead check whether first elt is not UNKNOWN_LOCATION and in that case pedwarn with the second location. * gimple-walk.cc (walk_gimple_seq_mod): Clear wi->removed_stmt after the flag has been used. * internal-fn.def (FALLTHROUGH): Mention in comment the special meaning of the TREE_NOTHROW/GF_CALL_NOTHROW flag on the calls. gcc/c-family/ * c-gimplify.cc (genericize_c_loop): For C++ mark IFN_FALLTHROU= GH call at the end of loop body as TREE_NOTHROW. gcc/testsuite/ * g++.dg/DRs/dr2406.C: New test.=