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<tree, 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_virtualDrat, this fix doesn't interact well with 'this'-capturing lambdas: struct BaseClass { void baseDevice(); // #1 void baseDevice() const = delete; // #2 }; template<class T> struct TopClass : T { void failsToCompile() { [this] { BaseClass::baseDevice(); }(); } }; template struct TopClass<BaseClass>; 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)?
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<class T> +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<BaseClass>; -- 2.36.1.182.g6afdb07b7b
