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[69.118.112.187]) by smtp.gmail.com with ESMTPSA id h4-20020ac87764000000b00304b41fa057sm4653324qtu.57.2022.06.03.07.46.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Jun 2022 07:46:50 -0700 (PDT) From: Patrick Palka X-Google-Original-From: Patrick Palka Date: Fri, 3 Jun 2022 10:46:50 -0400 (EDT) To: Jason Merrill cc: Patrick Palka , gcc-patches@gcc.gnu.org Subject: Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637] In-Reply-To: <7b8d13d3-cdab-a749-287a-8770e7f00d41@redhat.com> Message-ID: 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> <0fcce048-5e2c-4071-43e3-20f9fb72ba52@redhat.com> <7b8d13d3-cdab-a749-287a-8770e7f00d41@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII X-Spam-Status: No, score=-14.4 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, 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: Fri, 03 Jun 2022 14:46:56 -0000 On Thu, 2 Jun 2022, Jason Merrill wrote: > On 6/2/22 15:57, Patrick Palka wrote: > > On Thu, 2 Jun 2022, Jason Merrill wrote: > > > > > 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 > > > > > > > va_gc> > > > > > > > > **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. > > > > Unfortunately the lambda_function test is necessary to avoid crashing > > on lambda-ice11.C; the test mirrors what resolvable_dummy_lambda does > > ever since r207999 / r208028 to avoid the crash. > > Hmm, how about adjusting lambda_expr_this_capture to avoid the crash? I'm afraid I'm not sure how to do that :/ In particular for the case where add_capture_p is nonzero and the given lambda lacks a lambda_function. I suppose we can relax the assert in the !add_capture_p case but that seems somewhat hacky. I noticed that finish_this_expr, another user of lambda_expr_this_capture, isn't guarded by resolvable_dummy_lambda. I believe it gets away with this because it checks lambda-ness of TREE_TYPE (current_class_ref) instead of current_class_type. Perhaps we should do the same in maybe_dummy_object? This avoids the ICE in lambda-ice11.C without needing to check lambda_function, and seems like a cleaner approach overall. -- >8 -- Subject: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637] 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 | 31 ++++++++++++++----- .../g++.dg/cpp0x/lambda/lambda-this22.C | 20 ++++++++++++ .../g++.dg/template/non-dependent23.C | 25 +++++++++++++++ 3 files changed, 69 insertions(+), 7 deletions(-) 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 2b9cb7e1c7b..183febffb5d 100644 --- a/gcc/cp/tree.cc +++ b/gcc/cp/tree.cc @@ -4319,15 +4319,32 @@ maybe_dummy_object (tree type, tree* binfop) if (binfop) *binfop = binfo; - if (current_class_ref - /* current_class_ref might not correspond to current_class_type if - we're in tsubst_default_argument or a lambda-declarator; in either - case, we want to use current_class_ref if it matches CONTEXT. */ - && (same_type_ignoring_top_level_qualifiers_p - (TREE_TYPE (current_class_ref), context))) + /* current_class_ref might not correspond to current_class_type if + we're in tsubst_default_argument or a lambda-declarator; in either + case, we want to use current_class_ref if it matches CONTEXT. */ + tree ctype = current_class_ref ? TREE_TYPE (current_class_ref) : NULL_TREE; + if (ctype + && same_type_ignoring_top_level_qualifiers_p (ctype, 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 (ctype) + { + int quals = 0; + if (LAMBDA_TYPE_P (ctype)) + { + tree lambda = CLASSTYPE_LAMBDA_EXPR (ctype); + if (tree cap = lambda_expr_this_capture (lambda, false)) + quals = cp_type_quals (TREE_TYPE (TREE_TYPE (cap))); + } + else + quals = cp_type_quals (ctype); + 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; -- 2.36.1.210.g2668e3608e