From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 658D3395B400 for ; Thu, 2 Jun 2022 19:44:49 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 658D3395B400 Received: from mail-qk1-f200.google.com (mail-qk1-f200.google.com [209.85.222.200]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-644-skEea3B2OuyiHmLsNjis0Q-1; Thu, 02 Jun 2022 15:44:47 -0400 X-MC-Unique: skEea3B2OuyiHmLsNjis0Q-1 Received: by mail-qk1-f200.google.com with SMTP id bl27-20020a05620a1a9b00b0069994eeb30cso4417974qkb.11 for ; Thu, 02 Jun 2022 12:44:47 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=UIRCTjoyheMbVpUXRAUX3nmJ/tyoDTr5oXiu8mcMhoo=; b=qcPOKH5JeEovNUzpeQt1NBQLWXao0hRz41GJEl7oScHP7k2+/xcKn//qiG0UfCl4Fu ipEiBOGhZ3REvzlvy/xYgkZNygjD7r87n3U7N4VstJIR2KoD/LWX3wv2eH3zrR0pM3z2 1gl92DUCRdeFjgX7MZyQqD28WdjltgfIepBLraCnbaBICc/EJuiNuQafry7DhblsarOV zdTAUlHLdcnnmMcFjW6GweYrNqBVGHbyf0+4IcBHK+R2kFozyBi9oH/ZJ48zNY1HHUkx lqcHY6WuKIb+/U5MRIpqW5KztxpOKeF8OfNe6sgT1d7delN30/90gJPl9WgyAU8nJZKY EDEw== X-Gm-Message-State: AOAM533ntLGXuckv2mG0f5HxDysSqu+N0vXv/oyyNM01GwZ6/siE705+ yE7A5QrM4cn83W9T3fV4G7Q3zAVqSbn0FJGftqsVx1FNtE/9c+X1MJIT0o4qZ/QWa1yDr34ZzlT wpThr71ppEkw6GWU1hw== X-Received: by 2002:a37:a9d1:0:b0:6a3:736a:76d8 with SMTP id s200-20020a37a9d1000000b006a3736a76d8mr4522314qke.96.1654199087111; Thu, 02 Jun 2022 12:44:47 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxi0vUsDfj4qCE/4goI7/LWM3v5szCIa/zehTOHOMB5+8GwC6aoT+SdoYjhmfwS2IIc9PvYTA== X-Received: by 2002:a37:a9d1:0:b0:6a3:736a:76d8 with SMTP id s200-20020a37a9d1000000b006a3736a76d8mr4522299qke.96.1654199086630; Thu, 02 Jun 2022 12:44:46 -0700 (PDT) Received: from [192.168.1.100] (130-44-159-43.s15913.c3-0.arl-cbr1.sbo-arl.ma.cable.rcncustomer.com. [130.44.159.43]) by smtp.gmail.com with ESMTPSA id s2-20020a05620a080200b006a39e915252sm3660052qks.97.2022.06.02.12.44.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 02 Jun 2022 12:44:45 -0700 (PDT) Message-ID: <0fcce048-5e2c-4071-43e3-20f9fb72ba52@redhat.com> Date: Thu, 2 Jun 2022 15:44:44 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637] To: Patrick Palka Cc: gcc-patches@gcc.gnu.org References: <20220526183450.2331967-1-ppalka@redhat.com> <527705e5-b69c-f1bd-f531-6bb43e10713b@idea> <34d2cabf-523c-098d-633d-8e3d7619f8b1@redhat.com> <1874d5e6-8a87-2b90-d9a2-95be5831af16@idea> From: Jason Merrill In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-13.9 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Jun 2022 19:44:51 -0000 On 5/27/22 09:57, Patrick Palka wrote: > On Thu, 26 May 2022, Patrick Palka wrote: > >> On Thu, 26 May 2022, Jason Merrill wrote: >> >>> On 5/26/22 14:57, Patrick Palka wrote: >>>> On Thu, 26 May 2022, Patrick Palka wrote: >>>> >>>>> Here we expect the calls to BaseClass::baseDevice resolve to the second, >>>>> third and fourth overloads respectively in light of the cv-qualifiers >>>>> of 'this' in each case. But ever since r12-6075-g2decd2cabe5a4f, the >>>>> calls incorrectly resolve to the first overload at instantiation time. >>>>> >>>>> This happens because the calls to BaseClass::baseDevice are all deemed >>>>> non-dependent (ever since r7-755-g23cb72663051cd made us ignore the >>>>> dependentness of 'this' when considering the dependence of a non-static >>>>> memfn call), hence we end up checking the call ahead of time, using as >>>>> the object argument a dummy object of type BaseClass. Since this object >>>>> argument is cv-unqualified, the calls incoherently resolve to the first >>>>> overload of baseDevice. Before r12-6075, this incorrect result would >>>>> just get silently discarded and we'd end up redoing OR at instantiation >>>>> time using 'this' as the object argument. But after r12-6075, we now >>>>> reuse this incorrect result at instantiation time. >>>>> >>>>> This patch fixes this by making finish_call_expr request from >>>>> maybe_dummy_object a cv-qualified object consistent with the cv-quals of >>>>> 'this'. That way, ahead of time OR using a dummy object will give us >>>>> the right answer and we could safely reuse it at instantiation time. >>>>> >>>>> NB: r7-755 is also the cause of the related issue PR105742. Not sure >>>>> if there's a fix that could resolve both PRs at once.. >>>>> >>>>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK >>>>> for trunk/12? >>>>> >>>>> PR c++/105637 >>>>> >>>>> gcc/cp/ChangeLog: >>>>> >>>>> * semantics.cc (finish_call_expr): Pass a cv-qualified object >>>>> type to maybe_dummy_object that is consistent with the >>>>> cv-qualifiers of 'this' if available. >>>>> >>>>> gcc/testsuite/ChangeLog: >>>>> >>>>> * g++.dg/template/non-dependent23.C: New test. >>>>> --- >>>>> gcc/cp/semantics.cc | 15 ++++++++--- >>>>> .../g++.dg/template/non-dependent23.C | 25 +++++++++++++++++++ >>>>> 2 files changed, 37 insertions(+), 3 deletions(-) >>>>> create mode 100644 gcc/testsuite/g++.dg/template/non-dependent23.C >>>>> >>>>> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc >>>>> index cd7a2818feb..1d9348c6cf1 100644 >>>>> --- a/gcc/cp/semantics.cc >>>>> +++ b/gcc/cp/semantics.cc >>>>> @@ -2802,16 +2802,25 @@ finish_call_expr (tree fn, vec >>>>> **args, bool disallow_virtual, >>>>> [class.access.base] says that we need to convert 'this' to B* as >>>>> part of the access, so we pass 'B' to maybe_dummy_object. */ >>>>> + tree object_type = BINFO_TYPE (BASELINK_ACCESS_BINFO (fn)); >>>>> if (DECL_MAYBE_IN_CHARGE_CONSTRUCTOR_P (get_first_fn (fn))) >>>>> { >>>>> /* A constructor call always uses a dummy object. (This constructor >>>>> call which has the form A::A () is actually invalid and we are >>>>> going to reject it later in build_new_method_call.) */ >>>>> - object = build_dummy_object (BINFO_TYPE (BASELINK_ACCESS_BINFO >>>>> (fn))); >>>>> + object = build_dummy_object (object_type); >>>>> } >>>>> else >>>>> - object = maybe_dummy_object (BINFO_TYPE (BASELINK_ACCESS_BINFO (fn)), >>>>> - NULL); >>>>> + { >>>>> + if (current_class_ref) >>>>> + { >>>>> + /* Make sure that if maybe_dummy_object gives us a dummy object, >>>>> + it'll have the same cv-quals as '*this'. */ >>>>> + int quals = cp_type_quals (TREE_TYPE (current_class_ref)); >>>>> + object_type = cp_build_qualified_type (object_type, quals); >>>>> + } >>>>> + object = maybe_dummy_object (object_type, NULL); >>>>> + } >>>>> result = build_new_method_call (object, fn, args, NULL_TREE, >>>>> (disallow_virtual >>>> >>>> Drat, this fix doesn't interact well with 'this'-capturing lambdas: >>>> >>>> struct BaseClass { >>>> void baseDevice(); // #1 >>>> void baseDevice() const = delete; // #2 >>>> }; >>>> >>>> template >>>> struct TopClass : T { >>>> void failsToCompile() { >>>> [this] { BaseClass::baseDevice(); }(); >>>> } >>>> }; >>>> >>>> template struct TopClass; >>>> >>>> Here after the fix, we'd incorrectly select the const #2 overload at >>>> template definition time because current_class_ref is the const 'this' >>>> for the lambda rather than the non-const 'this' for TopClass.. I suppose >>>> we need something like current_nonlambda_class_type for getting at the >>>> innermost non-lambda 'this'? >>> >>> Do you want maybe_resolve_dummy (ob, false)? >> >> That sadly doesn't seem to work -- the object type is BaseClass which is >> not necessarily a base of the dependent TopClass, so >> resolvable_dummy_lambda returns NULL_TREE. I guess it would work at >> instantiation time though. > > Ah, what seems to work well is directly using lambda_expr_this_capture > instead of maybe_resolve_dummy. And we might as well handle this in > maybe_dummy_object for benefit of all callers. How does the following > look? Smoke tested with RUNTESTFLAGS="dg.exp=*.C", full bootstrap and > regtesting in progress. > > -- >8 -- > > Subject: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637] > > In non-dependent23.C below we expect the BaseClass::baseDevice calls to > resolve to the second, third and fourth overloads respectively in light > of the cv-qualifiers of 'this' in each case. But ever since > r12-6075-g2decd2cabe5a4f, the calls incorrectly resolve to the first > overload at instantiation time. > > This happens because the calls to BaseClass::baseDevice are all deemed > non-dependent (ever since r7-755-g23cb72663051cd made us ignore 'this' > dependence when considering the dependence of a non-static memfn call), > hence we end up checking the call ahead of time, using as the object > argument a dummy object of type BaseClass. Since this object argument > is cv-unqualified, the calls incoherently resolve to the first overload > of baseDevice. Before r12-6075, this incorrect result would just get > silently discarded and we'd end up redoing OR at instantiation time > using 'this' as the object argument. But after r12-6075, we now reuse > this incorrect result at instantiation time. > > This patch fixes this by making maybe_dummy_object respect the cv-quals > of (the non-lambda) 'this' when returning a dummy object. Thus, ahead > of time OR using a dummy object will give us the right answer that is > consistent with the instantiation time answer. > > An earlier version of this patch didn't handle 'this'-capturing lambdas > correctly, which caused us to mishandle lambda-this22.C below. > > PR c++/105637 > > gcc/cp/ChangeLog: > > * tree.cc (maybe_dummy_object): When returning a dummy > object, respect the cv-quals of 'this' if available. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp0x/lambda/lambda-this22.C: New test. > * g++.dg/template/non-dependent23.C: New test. > --- > gcc/cp/tree.cc | 19 +++++++++++++- > .../g++.dg/cpp0x/lambda/lambda-this22.C | 20 +++++++++++++++ > .../g++.dg/template/non-dependent23.C | 25 +++++++++++++++++++ > 3 files changed, 63 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this22.C > create mode 100644 gcc/testsuite/g++.dg/template/non-dependent23.C > > diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc > index 09162795801..679bf05b721 100644 > --- a/gcc/cp/tree.cc > +++ b/gcc/cp/tree.cc > @@ -4330,7 +4330,24 @@ maybe_dummy_object (tree type, tree* binfop) > (TREE_TYPE (current_class_ref), context))) > decl = current_class_ref; > else > - decl = build_dummy_object (context); > + { > + /* Return a dummy object whose cv-quals are consistent with (the > + non-lambda) 'this' if available. */ > + if (current_class_ref) > + { > + int quals = 0; > + if (current == current_class_type) > + quals = cp_type_quals (TREE_TYPE (current_class_ref)); > + else if (lambda_function (current_class_type)) > + { > + tree lambda = CLASSTYPE_LAMBDA_EXPR (current_class_type); How about else if (tree lambda = CLASSTYPE_LAMBDA_EXPR (current_class_type)) ? OK with that change. > + if (tree cap = lambda_expr_this_capture (lambda, false)) > + quals = cp_type_quals (TREE_TYPE (TREE_TYPE (cap))); > + } > + context = cp_build_qualified_type (context, quals); > + } > + decl = build_dummy_object (context); > + } > > return decl; > } > diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this22.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this22.C > new file mode 100644 > index 00000000000..c9e512b1621 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-this22.C > @@ -0,0 +1,20 @@ > +// PR c++/105637 > +// { dg-do compile { target c++11 } } > + > +struct BaseClass { > + void baseDevice(); // #1 > + void baseDevice() const = delete; // #2 > +}; > + > +template > +struct TopClass : T { > + void failsToCompile() { > + [this] { BaseClass::baseDevice(); }(); // should select #2, not #1 > + } > + > + void failsToCompile() const { > + [this] { BaseClass::baseDevice(); }(); // { dg-error "deleted" } > + } > +}; > + > +template struct TopClass; > diff --git a/gcc/testsuite/g++.dg/template/non-dependent23.C b/gcc/testsuite/g++.dg/template/non-dependent23.C > new file mode 100644 > index 00000000000..ef95c591b75 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/template/non-dependent23.C > @@ -0,0 +1,25 @@ > +// PR c++/105637 > + > +struct BaseClass { > + void baseDevice(); // #1 > + void baseDevice() const; // #2 > + void baseDevice() volatile; // #3 > + void baseDevice() const volatile; // #4 > +}; > + > +template > +struct TopClass : T { > + void failsToCompile() const { > + BaseClass::baseDevice(); // should select #2, not #1 > + } > + > + void failsToCompile() volatile { > + BaseClass::baseDevice(); // should select #3, not #1 > + } > + > + void failsToCompile() const volatile { > + BaseClass::baseDevice(); // should select #4, not #1 > + } > +}; > + > +template struct TopClass;