From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2140) id 5182B385840D; Sun, 19 Nov 2023 05:25:48 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 5182B385840D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1700371548; bh=4Y5rNUc5yEN9u25df2l6nUVlhwtiBMmAmMsMETjDwZ0=; h=From:To:Subject:Date:From; b=vT3rxwVGD+7hV0iAZMlS1lxZkBe10bfVqi8qAdZ5ziv4Vx0kHOfFFnm3OZpuvOEnZ M94wXgb7RdFEkDiFuf8FRc4O0T28djsUC5lwOr9gVV5oJBqE7QXV3wS686nnROJJu0 gE00tWVuQSbjf+YYkcuhrCk8T8ZFn94GDyELg3CA= 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: 01de24b7060fef520c408be813ed202717174dac X-Git-Newrev: 0b4f16ab66a981f8d8a9a739a8f6508012401658 Message-Id: <20231119052548.5182B385840D@sourceware.org> Date: Sun, 19 Nov 2023 05:25:48 +0000 (GMT) List-Id: https://gcc.gnu.org/g:0b4f16ab66a981f8d8a9a739a8f6508012401658 commit 0b4f16ab66a981f8d8a9a739a8f6508012401658 Author: Alexandre Oliva Date: Sat Nov 18 02:32:05 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 9d4d95f85bf..1abf5d90edc 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 1fa710d7154..e1abb2a79dd 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -6956,6 +6956,7 @@ 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 d2ed46b1453..038c5ab71f2 100644 --- a/gcc/cp/decl.cc +++ b/gcc/cp/decl.cc @@ -17896,16 +17896,31 @@ 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". }