[PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Patrick Palka]

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_virtual
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

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Patrick Palka]

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_virtual

Drat, 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'?


> 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
> 
> 

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Jason Merrill]

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_virtual
> 
> Drat, 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
>>
>>
> 

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Patrick Palka]

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<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_virtual
> > 
> > Drat, 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)?

That sadly doesn't seem to work -- the object type is BaseClass which is
not necessarily a base of the dependent TopClass<T>, so
resolvable_dummy_lambda returns NULL_TREE.  I guess it would work at
instantiation time though.

> 
> > > 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
> > > 
> > > 
> > 
> 
> 

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Patrick Palka]

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<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_virtual
> > > 
> > > Drat, 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)?
> 
> That sadly doesn't seem to work -- the object type is BaseClass which is
> not necessarily a base of the dependent TopClass<T>, 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);
+	      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<class T>
+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<BaseClass>;
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>;
-- 
2.36.1.195.g8ddf593a25


> 
> > 
> > > > 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
> > > > 
> > > > 
> > > 
> > 
> > 
> 

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Patrick Palka]

On Fri, 27 May 2022, 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<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_virtual
> > > > 
> > > > Drat, 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)?
> > 
> > That sadly doesn't seem to work -- the object type is BaseClass which is
> > not necessarily a base of the dependent TopClass<T>, 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.

Ping.

> 
> 	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);
> +	      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<class T>
> +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<BaseClass>;
> 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>;
> -- 
> 2.36.1.195.g8ddf593a25
> 
> 
> > 
> > > 
> > > > > 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
> > > > > 
> > > > > 
> > > > 
> > > 
> > > 
> > 
> 

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Jason Merrill]

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<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_virtual
>>>>
>>>> Drat, 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)?
>>
>> That sadly doesn't seem to work -- the object type is BaseClass which is
>> not necessarily a base of the dependent TopClass<T>, 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<class T>
> +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<BaseClass>;
> 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>;

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Patrick Palka]

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<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_virtual
> > > > > 
> > > > > Drat, 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)?
> > > 
> > > That sadly doesn't seem to work -- the object type is BaseClass which is
> > > not necessarily a base of the dependent TopClass<T>, 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.

> 
> 
> > +	      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<class T>
> > +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<BaseClass>;
> > 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>;
> 
> 

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Jason Merrill]

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<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_virtual
>>>>>>
>>>>>> Drat, 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)?
>>>>
>>>> That sadly doesn't seem to work -- the object type is BaseClass which is
>>>> not necessarily a base of the dependent TopClass<T>, 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?

>>> +	      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<class T>
>>> +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<BaseClass>;
>>> 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>;
>>
>>
> 

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Patrick Palka]

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<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_virtual
> > > > > > > 
> > > > > > > Drat, 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)?
> > > > > 
> > > > > That sadly doesn't seem to work -- the object type is BaseClass which
> > > > > is
> > > > > not necessarily a base of the dependent TopClass<T>, 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<class T>
+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<BaseClass>;
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>;
-- 
2.36.1.210.g2668e3608e

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Jason Merrill]

On 6/3/22 10:46, Patrick Palka wrote:
> 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<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_virtual
>>>>>>>>
>>>>>>>> Drat, 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)?
>>>>>>
>>>>>> That sadly doesn't seem to work -- the object type is BaseClass which
>>>>>> is
>>>>>> not necessarily a base of the dependent TopClass<T>, 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);

And just checking CLASSTYPE_LAMBDA_EXPR (ctype) still isn't enough?

> +	      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<class T>
> +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<BaseClass>;
> 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>;

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Patrick Palka]

On Fri, 3 Jun 2022, Jason Merrill wrote:

> On 6/3/22 10:46, Patrick Palka wrote:
> > 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<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_virtual
> > > > > > > > > 
> > > > > > > > > Drat, 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)?
> > > > > > > 
> > > > > > > That sadly doesn't seem to work -- the object type is BaseClass
> > > > > > > which
> > > > > > > is
> > > > > > > not necessarily a base of the dependent TopClass<T>, 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);
> 
> And just checking CLASSTYPE_LAMBDA_EXPR (ctype) still isn't enough?

Whoops, it appears to be enough now.  I was under the mistaken
impression that CLASSTYPE_LAMBDA_EXPR is only usable for LAMBDA_TYPE_P
types.  So like so (full bootstrap/testing in progress):

-- >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                                | 30 ++++++++++++++-----
 .../g++.dg/cpp0x/lambda/lambda-this22.C       | 20 +++++++++++++
 .../g++.dg/template/non-dependent23.C         | 25 ++++++++++++++++
 3 files changed, 68 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..fa9c472efac 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -4319,15 +4319,31 @@ 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 (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..8c6afe06cac
--- /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 Base {
+  void foo();                // #1
+  void foo() const = delete; // #2
+};
+
+template<class T>
+struct TopClass : T {
+  void failsToCompile() {
+    [this] { Base::foo(); }(); // should select #2, not #1
+  }
+
+  void failsToCompile() const {
+    [this] { Base::foo(); }(); // { dg-error "deleted" }
+  }
+};
+
+template struct TopClass<Base>;
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..885a641a655
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/non-dependent23.C
@@ -0,0 +1,25 @@
+// PR c++/105637
+
+struct Base {
+  void foo();                // #1
+  void foo() const;          // #2
+  void foo() volatile;       // #3
+  void foo() const volatile; // #4
+};
+
+template<class T>
+struct TopClass : T {
+  void failsToCompile() const {
+    Base::foo(); // should select #2, not #1
+  }
+
+  void failsToCompile() volatile {
+    Base::foo();  // should select #3, not #1
+  }
+
+  void failsToCompile() const volatile {
+    Base::foo();  // should select #4, not #1
+  }
+};
+
+template struct TopClass<Base>;
-- 
2.36.1.210.g2668e3608e

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Jason Merrill]

On 6/3/22 11:04, Patrick Palka wrote:
> On Fri, 3 Jun 2022, Jason Merrill wrote:
> 
>> On 6/3/22 10:46, Patrick Palka wrote:
>>> 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<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_virtual
>>>>>>>>>>
>>>>>>>>>> Drat, 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)?
>>>>>>>>
>>>>>>>> That sadly doesn't seem to work -- the object type is BaseClass
>>>>>>>> which
>>>>>>>> is
>>>>>>>> not necessarily a base of the dependent TopClass<T>, 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);
>>
>> And just checking CLASSTYPE_LAMBDA_EXPR (ctype) still isn't enough?
> 
> Whoops, it appears to be enough now.  I was under the mistaken
> impression that CLASSTYPE_LAMBDA_EXPR is only usable for LAMBDA_TYPE_P
> types.  So like so (full bootstrap/testing in progress):

OK.

> -- >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                                | 30 ++++++++++++++-----
>   .../g++.dg/cpp0x/lambda/lambda-this22.C       | 20 +++++++++++++
>   .../g++.dg/template/non-dependent23.C         | 25 ++++++++++++++++
>   3 files changed, 68 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..fa9c472efac 100644
> --- a/gcc/cp/tree.cc
> +++ b/gcc/cp/tree.cc
> @@ -4319,15 +4319,31 @@ 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 (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..8c6afe06cac
> --- /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 Base {
> +  void foo();                // #1
> +  void foo() const = delete; // #2
> +};
> +
> +template<class T>
> +struct TopClass : T {
> +  void failsToCompile() {
> +    [this] { Base::foo(); }(); // should select #2, not #1
> +  }
> +
> +  void failsToCompile() const {
> +    [this] { Base::foo(); }(); // { dg-error "deleted" }
> +  }
> +};
> +
> +template struct TopClass<Base>;
> 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..885a641a655
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/non-dependent23.C
> @@ -0,0 +1,25 @@
> +// PR c++/105637
> +
> +struct Base {
> +  void foo();                // #1
> +  void foo() const;          // #2
> +  void foo() volatile;       // #3
> +  void foo() const volatile; // #4
> +};
> +
> +template<class T>
> +struct TopClass : T {
> +  void failsToCompile() const {
> +    Base::foo(); // should select #2, not #1
> +  }
> +
> +  void failsToCompile() volatile {
> +    Base::foo();  // should select #3, not #1
> +  }
> +
> +  void failsToCompile() const volatile {
> +    Base::foo();  // should select #4, not #1
> +  }
> +};
> +
> +template struct TopClass<Base>;

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Marek Polacek]

On Fri, Jun 03, 2022 at 11:16:26AM -0400, Jason Merrill via Gcc-patches wrote:
> On 6/3/22 11:04, Patrick Palka wrote:
> > > > @@ -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;

Sorry to nitpick, but this 0 could be TYPE_UNQUALIFIED.

Marek

Re: [PATCH] c++: cv-quals of dummy obj for non-dep memfn call [PR105637]

[Patrick Palka]

On Fri, 3 Jun 2022, Marek Polacek wrote:

> On Fri, Jun 03, 2022 at 11:16:26AM -0400, Jason Merrill via Gcc-patches wrote:
> > On 6/3/22 11:04, Patrick Palka wrote:
> > > > > @@ -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;
> 
> Sorry to nitpick, but this 0 could be TYPE_UNQUALIFIED.

Good point, fixed.

> 
> Marek
> 
>