From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2140) id ED0F93858036; Wed, 29 Nov 2023 04:35:21 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org ED0F93858036 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1701232521; bh=mtPv1cYcwbOLpnP7KUYSseet2wTxWwH7RJjUXSRzkK0=; h=From:To:Subject:Date:From; b=Px7Jx855SXml5z0/6B1LJu+7NsmtT4s6ACjBOxsWC5jATYlKxCybQu2//fbK/4E0W uu1C0fZOGRAKhbPVVS0hAA7fgzPdCNJZzpE3kUxdXEozP3KNOFxvykW2OETwYRXK61 NOU0v9RRfc5QRzUAaKQW7yGRSk7OPQwFY+NCRuZY= Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Alexandre Oliva To: gcc-cvs@gcc.gnu.org Subject: [gcc(refs/users/aoliva/heads/testme)] call maybe_return_this in build_clone X-Act-Checkin: gcc X-Git-Author: Alexandre Oliva X-Git-Refname: refs/users/aoliva/heads/testme X-Git-Oldrev: 554f30e1af04d885fbd149561c526af572b0cbc4 X-Git-Newrev: 177f6f2b2283bb92b8cbb78ca69f67eab7d52ef1 Message-Id: <20231129043521.ED0F93858036@sourceware.org> Date: Wed, 29 Nov 2023 04:35:21 +0000 (GMT) List-Id: https://gcc.gnu.org/g:177f6f2b2283bb92b8cbb78ca69f67eab7d52ef1 commit 177f6f2b2283bb92b8cbb78ca69f67eab7d52ef1 Author: Alexandre Oliva Date: Wed Nov 29 00:54:47 2023 -0300 call maybe_return_this in build_clone __dt_base doesn't get its body from a maybe_return_this caller, it's rather cloned with the full body within build_clone, and then it's left alone, without going through finish_function_body or build_delete_destructor_body, that call maybe_return_this. Now, this is correct as far as the generated code is concerned, since the cloned body of a cdtor that returns this is also a cdtor body that returns this. The problem is that the decl for THIS is also cloned, and it doesn't get the warning suppression introduced by maybe_return_this, so Wuse-after-free3.C fails with an excess warning at the closing brace of the dtor body. I've split out the warning suppression from maybe_return_this, and arranged to call that bit from the relevant build_clone case. Unfortunately, because the warning is silenced for all uses of the THIS decl, rather than only for the ABI-mandated return stmt, this also silences the very warning that the testcase checks for. I'm not revamping the warning suppression approach to overcome this, so I'm xfailing the expected warning on ARM EABI, hoping that's the only target with cdtor_return_this, and leaving it at that. for gcc/cp/ChangeLog * decl.cc (maybe_prepare_return_this): Split out of... (maybe_return_this): ... this. * cp-tree.h (maybe_prepare_return_this): Declare. * class.cc (build_clone): Call it. for gcc/testsuite/ChangeLog * g++.dg/warn/Wuse-after-free3.C: xfail on arm_eabi. Diff: --- gcc/cp/class.cc | 2 ++ gcc/cp/cp-tree.h | 1 + gcc/cp/decl.cc | 23 +++++++++++++++++++---- gcc/testsuite/g++.dg/warn/Wuse-after-free3.C | 4 +++- 4 files changed, 25 insertions(+), 5 deletions(-) diff --git a/gcc/cp/class.cc b/gcc/cp/class.cc index 4766b7cf832..6fdb56abfb9 100644 --- a/gcc/cp/class.cc +++ b/gcc/cp/class.cc @@ -5053,6 +5053,8 @@ build_clone (tree fn, tree name, bool need_vtt_parm_p, clone = copy_fndecl_with_name (fn, name, ERROR_MARK, need_vtt_parm_p, omit_inherited_parms_p); DECL_CLONED_FUNCTION (clone) = fn; + + maybe_prepare_return_this (clone); } /* Remember where this function came from. */ diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h index 7b0b7c6a17e..5614b71eed4 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -6979,6 +6979,7 @@ extern tree lookup_enumerator (tree, tree); extern bool start_preparsed_function (tree, tree, int); extern bool start_function (cp_decl_specifier_seq *, const cp_declarator *, tree); +extern tree maybe_prepare_return_this (tree); extern void maybe_return_this (void); extern tree begin_function_body (void); extern void finish_function_body (tree); diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc index e269f689c1c..bce806819d5 100644 --- a/gcc/cp/decl.cc +++ b/gcc/cp/decl.cc @@ -17926,16 +17926,31 @@ store_parm_decls (tree current_function_parms) } +/* Mark CDTOR's implicit THIS argument for returning, if required by + the ABI.. Return the decl for THIS, if it is to be returned, and + NULL otherwise. */ + +tree +maybe_prepare_return_this (tree cdtor) +{ + if (targetm.cxx.cdtor_returns_this ()) + if (tree val = DECL_ARGUMENTS (cdtor)) + { + suppress_warning (val, OPT_Wuse_after_free); + return val; + } + + return NULL_TREE; +} + /* Set the return value of the [cd]tor if the ABI wants that. */ void -maybe_return_this (void) +maybe_return_this () { - if (targetm.cxx.cdtor_returns_this ()) + if (tree val = maybe_prepare_return_this (current_function_decl)) { /* Return the address of the object. */ - tree val = DECL_ARGUMENTS (current_function_decl); - suppress_warning (val, OPT_Wuse_after_free); val = fold_convert (TREE_TYPE (DECL_RESULT (current_function_decl)), val); val = build2 (MODIFY_EXPR, TREE_TYPE (val), DECL_RESULT (current_function_decl), val); diff --git a/gcc/testsuite/g++.dg/warn/Wuse-after-free3.C b/gcc/testsuite/g++.dg/warn/Wuse-after-free3.C index e5b157865bf..8ef82021380 100644 --- a/gcc/testsuite/g++.dg/warn/Wuse-after-free3.C +++ b/gcc/testsuite/g++.dg/warn/Wuse-after-free3.C @@ -11,5 +11,7 @@ struct A A::~A () { operator delete (this); - f (); // { dg-warning "used after" } + f (); // { dg-warning "used after" "" { xfail arm_eabi } } + // arm_eabi's cdtors return this, which disables -Wuse-after-free + // warnings for cdtors' "this". }