* [PATCH] c++: Fix access checking of scoped non-static member [PR98515] @ 2021-01-06 18:19 Patrick Palka 2021-01-07 21:37 ` Jason Merrill 0 siblings, 1 reply; 5+ messages in thread From: Patrick Palka @ 2021-01-06 18:19 UTC (permalink / raw) To: gcc-patches In the first testcase below, we incorrectly reject the use of the protected non-static member A::var0 from C<int>::g() because check_accessibility_of_qualified_id, at template parse time, determines that the access doesn't go through 'this'. (This happens because the dependent base B<T> of C<T> doesn't have a binfo object, so it appears to DERIVED_FROM_P that A is not an indirect base of C<T>.) From there we create the corresponding deferred access check, which we then perform at instantiation time and which (unsurprisingly) fails. The problem ultimately seems to be that we can't, in general, know whether a use of a scoped non-static member goes through 'this' until instantiation time, as the second testcase below demonstrates. So this patch makes check_accessibility_of_qualified_id punt in this situation. Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK to commit? gcc/cp/ChangeLog: PR c++/98515 * semantics.c (check_accessibility_of_qualified_id): Punt if we're checking the access of a scoped non-static member at class template parse time. gcc/testsuite/ChangeLog: PR c++/98515 * g++.dg/template/access32.C: New test. * g++.dg/template/access33.C: New test. --- gcc/cp/semantics.c | 20 +++++++++++++++----- gcc/testsuite/g++.dg/template/access32.C | 8 ++++++++ gcc/testsuite/g++.dg/template/access33.C | 9 +++++++++ 3 files changed, 32 insertions(+), 5 deletions(-) create mode 100644 gcc/testsuite/g++.dg/template/access32.C create mode 100644 gcc/testsuite/g++.dg/template/access33.C diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c index b448efe024a..f52b2e4d1e7 100644 --- a/gcc/cp/semantics.c +++ b/gcc/cp/semantics.c @@ -2107,14 +2107,24 @@ check_accessibility_of_qualified_id (tree decl, /* If the reference is to a non-static member of the current class, treat it as if it were referenced through `this'. */ - tree ct; if (DECL_NONSTATIC_MEMBER_P (decl) - && current_class_ptr - && DERIVED_FROM_P (scope, ct = current_nonlambda_class_type ())) - qualifying_type = ct; + && current_class_ptr) + { + if (dependent_type_p (TREE_TYPE (current_class_ptr))) + /* In general we can't know whether this access goes through `this' + until instantiation of the current class. Punt now, or else + we might create a deferred access check that's relative to the + wrong class. We'll check this access again after substitution, + e.g. from tsubst_qualified_id. */ + return true; + + if (tree current = current_nonlambda_class_type ()) + if (DERIVED_FROM_P (scope, current)) + qualifying_type = current; + } /* Otherwise, use the type indicated by the nested-name-specifier. */ - else + if (!qualifying_type) qualifying_type = nested_name_specifier; } else diff --git a/gcc/testsuite/g++.dg/template/access32.C b/gcc/testsuite/g++.dg/template/access32.C new file mode 100644 index 00000000000..08faa9f0f97 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/access32.C @@ -0,0 +1,8 @@ +// PR c++/98515 +// { dg-do compile } + +struct A { protected: int var0; }; +template <class> struct B : public A { }; +template <class T> struct C : public B<T> { void g(); }; +template <class T> void C<T>::g() { A::var0++; } +template class C<int>; diff --git a/gcc/testsuite/g++.dg/template/access33.C b/gcc/testsuite/g++.dg/template/access33.C new file mode 100644 index 00000000000..9fb9b9a1236 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/access33.C @@ -0,0 +1,9 @@ +// PR c++/98515 +// { dg-do compile } + +struct A { protected: int var0; }; +template <class> struct B : public A { }; +template <class T> struct C : public B<T> { void g(); }; +template <class T> void C<T>::g() { A::var0++; } // { dg-error "protected|invalid" } +template <> struct B<char> { }; +template class C<char>; -- 2.30.0 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] c++: Fix access checking of scoped non-static member [PR98515] 2021-01-06 18:19 [PATCH] c++: Fix access checking of scoped non-static member [PR98515] Patrick Palka @ 2021-01-07 21:37 ` Jason Merrill 2021-01-07 22:47 ` Patrick Palka 0 siblings, 1 reply; 5+ messages in thread From: Jason Merrill @ 2021-01-07 21:37 UTC (permalink / raw) To: Patrick Palka, gcc-patches On 1/6/21 1:19 PM, Patrick Palka wrote: > In the first testcase below, we incorrectly reject the use of the > protected non-static member A::var0 from C<int>::g() because > check_accessibility_of_qualified_id, at template parse time, determines > that the access doesn't go through 'this'. (This happens because the > dependent base B<T> of C<T> doesn't have a binfo object, so it appears > to DERIVED_FROM_P that A is not an indirect base of C<T>.) From there > we create the corresponding deferred access check, which we then > perform at instantiation time and which (unsurprisingly) fails. > > The problem ultimately seems to be that we can't, in general, know > whether a use of a scoped non-static member goes through 'this' until > instantiation time, as the second testcase below demonstrates. So this > patch makes check_accessibility_of_qualified_id punt in this situation. > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK to > commit? > > gcc/cp/ChangeLog: > > PR c++/98515 > * semantics.c (check_accessibility_of_qualified_id): Punt if > we're checking the access of a scoped non-static member at > class template parse time. > > gcc/testsuite/ChangeLog: > > PR c++/98515 > * g++.dg/template/access32.C: New test. > * g++.dg/template/access33.C: New test. > --- > gcc/cp/semantics.c | 20 +++++++++++++++----- > gcc/testsuite/g++.dg/template/access32.C | 8 ++++++++ > gcc/testsuite/g++.dg/template/access33.C | 9 +++++++++ > 3 files changed, 32 insertions(+), 5 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/template/access32.C > create mode 100644 gcc/testsuite/g++.dg/template/access33.C > > diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c > index b448efe024a..f52b2e4d1e7 100644 > --- a/gcc/cp/semantics.c > +++ b/gcc/cp/semantics.c > @@ -2107,14 +2107,24 @@ check_accessibility_of_qualified_id (tree decl, > /* If the reference is to a non-static member of the > current class, treat it as if it were referenced through > `this'. */ > - tree ct; > if (DECL_NONSTATIC_MEMBER_P (decl) > - && current_class_ptr > - && DERIVED_FROM_P (scope, ct = current_nonlambda_class_type ())) > - qualifying_type = ct; > + && current_class_ptr) > + { > + if (dependent_type_p (TREE_TYPE (current_class_ptr))) This should also look at current_nonlambda_class_type. > + /* In general we can't know whether this access goes through `this' > + until instantiation of the current class. Punt now, or else > + we might create a deferred access check that's relative to the > + wrong class. We'll check this access again after substitution, > + e.g. from tsubst_qualified_id. */ > + return true; > + > + if (tree current = current_nonlambda_class_type ()) > + if (DERIVED_FROM_P (scope, current)) > + qualifying_type = current; > + } > /* Otherwise, use the type indicated by the > nested-name-specifier. */ > - else > + if (!qualifying_type) > qualifying_type = nested_name_specifier; > } > else > diff --git a/gcc/testsuite/g++.dg/template/access32.C b/gcc/testsuite/g++.dg/template/access32.C > new file mode 100644 > index 00000000000..08faa9f0f97 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/template/access32.C > @@ -0,0 +1,8 @@ > +// PR c++/98515 > +// { dg-do compile } > + > +struct A { protected: int var0; }; > +template <class> struct B : public A { }; > +template <class T> struct C : public B<T> { void g(); }; > +template <class T> void C<T>::g() { A::var0++; } > +template class C<int>; > diff --git a/gcc/testsuite/g++.dg/template/access33.C b/gcc/testsuite/g++.dg/template/access33.C > new file mode 100644 > index 00000000000..9fb9b9a1236 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/template/access33.C > @@ -0,0 +1,9 @@ > +// PR c++/98515 > +// { dg-do compile } > + > +struct A { protected: int var0; }; > +template <class> struct B : public A { }; > +template <class T> struct C : public B<T> { void g(); }; > +template <class T> void C<T>::g() { A::var0++; } // { dg-error "protected|invalid" } > +template <> struct B<char> { }; > +template class C<char>; > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] c++: Fix access checking of scoped non-static member [PR98515] 2021-01-07 21:37 ` Jason Merrill @ 2021-01-07 22:47 ` Patrick Palka 2021-01-08 1:12 ` Jason Merrill 0 siblings, 1 reply; 5+ messages in thread From: Patrick Palka @ 2021-01-07 22:47 UTC (permalink / raw) To: Jason Merrill; +Cc: Patrick Palka, gcc-patches On Thu, 7 Jan 2021, Jason Merrill wrote: > On 1/6/21 1:19 PM, Patrick Palka wrote: > > In the first testcase below, we incorrectly reject the use of the > > protected non-static member A::var0 from C<int>::g() because > > check_accessibility_of_qualified_id, at template parse time, determines > > that the access doesn't go through 'this'. (This happens because the > > dependent base B<T> of C<T> doesn't have a binfo object, so it appears > > to DERIVED_FROM_P that A is not an indirect base of C<T>.) From there > > we create the corresponding deferred access check, which we then > > perform at instantiation time and which (unsurprisingly) fails. > > > > The problem ultimately seems to be that we can't, in general, know > > whether a use of a scoped non-static member goes through 'this' until > > instantiation time, as the second testcase below demonstrates. So this > > patch makes check_accessibility_of_qualified_id punt in this situation. > > > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK to > > commit? > > > > gcc/cp/ChangeLog: > > > > PR c++/98515 > > * semantics.c (check_accessibility_of_qualified_id): Punt if > > we're checking the access of a scoped non-static member at > > class template parse time. > > > > gcc/testsuite/ChangeLog: > > > > PR c++/98515 > > * g++.dg/template/access32.C: New test. > > * g++.dg/template/access33.C: New test. > > --- > > gcc/cp/semantics.c | 20 +++++++++++++++----- > > gcc/testsuite/g++.dg/template/access32.C | 8 ++++++++ > > gcc/testsuite/g++.dg/template/access33.C | 9 +++++++++ > > 3 files changed, 32 insertions(+), 5 deletions(-) > > create mode 100644 gcc/testsuite/g++.dg/template/access32.C > > create mode 100644 gcc/testsuite/g++.dg/template/access33.C > > > > diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c > > index b448efe024a..f52b2e4d1e7 100644 > > --- a/gcc/cp/semantics.c > > +++ b/gcc/cp/semantics.c > > @@ -2107,14 +2107,24 @@ check_accessibility_of_qualified_id (tree decl, > > /* If the reference is to a non-static member of the > > current class, treat it as if it were referenced through > > `this'. */ > > - tree ct; > > if (DECL_NONSTATIC_MEMBER_P (decl) > > - && current_class_ptr > > - && DERIVED_FROM_P (scope, ct = current_nonlambda_class_type ())) > > - qualifying_type = ct; > > + && current_class_ptr) > > + { > > + if (dependent_type_p (TREE_TYPE (current_class_ptr))) > > This should also look at current_nonlambda_class_type. Ah, ack. But it seems to me we really only need to be checking dependence of current_nonlambda_class_type here. IIUC, dependence of these two types should coincide except in the case where we're inside a generic lambda within a non-template class (in which case current_class_ptr will dependent and current_nonlambda_class_type won't). But in this case we have enough information to be able to resolve the access check at parse time, I think (and so we shouldn't punt). The below patch, which seems to pass 'make check-c++', checks the dependence of current_nonlambda_class_type instead of that of current_class_ptr. Does this approach seem right? -- >8 -- Subject: [PATCH] c++: Fix access checking of scoped non-static member [PR98515] In the first testcase below, we incorrectly reject the use of the protected non-static member A::var0 from C<int>::g() because check_accessibility_of_qualified_id, at template parse time, determines that the access doesn't go through 'this'. (This happens because the dependent base B<T> of C<T> doesn't have a binfo object, so it appears to DERIVED_FROM_P that A is not an indirect base of C<T>.) From there we create the corresponding deferred access check, which we then perform at instantiation time and which (unsurprisingly) fails. The problem ultimately seems to be that we can't in general determine whether a use of a scoped non-static member goes through 'this' until instantiation time, as the second testcase below illustrates. So this patch makes check_accessibility_of_qualified_id punt in such situations to avoid creating a bogus deferred access check. gcc/cp/ChangeLog: PR c++/98515 * semantics.c (check_accessibility_of_qualified_id): Punt if we're checking access of a scoped non-static member inside a class template. gcc/testsuite/ChangeLog: PR c++/98515 * g++.dg/template/access32.C: New test. * g++.dg/template/access33.C: New test. --- gcc/cp/semantics.c | 22 +++++++++++++++++----- gcc/testsuite/g++.dg/template/access32.C | 8 ++++++++ gcc/testsuite/g++.dg/template/access33.C | 9 +++++++++ 3 files changed, 34 insertions(+), 5 deletions(-) create mode 100644 gcc/testsuite/g++.dg/template/access32.C create mode 100644 gcc/testsuite/g++.dg/template/access33.C diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c index b448efe024a..51f7c114b03 100644 --- a/gcc/cp/semantics.c +++ b/gcc/cp/semantics.c @@ -2107,14 +2107,26 @@ check_accessibility_of_qualified_id (tree decl, /* If the reference is to a non-static member of the current class, treat it as if it were referenced through `this'. */ - tree ct; if (DECL_NONSTATIC_MEMBER_P (decl) - && current_class_ptr - && DERIVED_FROM_P (scope, ct = current_nonlambda_class_type ())) - qualifying_type = ct; + && current_class_ptr) + { + if (tree current = current_nonlambda_class_type ()) + { + if (dependent_type_p (current)) + /* In general we can't know whether this access goes through + `this' until instantiation time. Punt now, or else we might + create a deferred access check that's not relative to 'this' + when it ought to be. We'll check this access again after + substitution, e.g. from tsubst_qualified_id. */ + return true; + + if (DERIVED_FROM_P (scope, current)) + qualifying_type = current; + } + } /* Otherwise, use the type indicated by the nested-name-specifier. */ - else + if (!qualifying_type) qualifying_type = nested_name_specifier; } else diff --git a/gcc/testsuite/g++.dg/template/access32.C b/gcc/testsuite/g++.dg/template/access32.C new file mode 100644 index 00000000000..08faa9f0f97 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/access32.C @@ -0,0 +1,8 @@ +// PR c++/98515 +// { dg-do compile } + +struct A { protected: int var0; }; +template <class> struct B : public A { }; +template <class T> struct C : public B<T> { void g(); }; +template <class T> void C<T>::g() { A::var0++; } +template class C<int>; diff --git a/gcc/testsuite/g++.dg/template/access33.C b/gcc/testsuite/g++.dg/template/access33.C new file mode 100644 index 00000000000..9fb9b9a1236 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/access33.C @@ -0,0 +1,9 @@ +// PR c++/98515 +// { dg-do compile } + +struct A { protected: int var0; }; +template <class> struct B : public A { }; +template <class T> struct C : public B<T> { void g(); }; +template <class T> void C<T>::g() { A::var0++; } // { dg-error "protected|invalid" } +template <> struct B<char> { }; +template class C<char>; -- 2.30.0 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] c++: Fix access checking of scoped non-static member [PR98515] 2021-01-07 22:47 ` Patrick Palka @ 2021-01-08 1:12 ` Jason Merrill 2021-01-08 15:39 ` Patrick Palka 0 siblings, 1 reply; 5+ messages in thread From: Jason Merrill @ 2021-01-08 1:12 UTC (permalink / raw) To: Patrick Palka; +Cc: gcc-patches On 1/7/21 5:47 PM, Patrick Palka wrote: > On Thu, 7 Jan 2021, Jason Merrill wrote: > >> On 1/6/21 1:19 PM, Patrick Palka wrote: >>> In the first testcase below, we incorrectly reject the use of the >>> protected non-static member A::var0 from C<int>::g() because >>> check_accessibility_of_qualified_id, at template parse time, determines >>> that the access doesn't go through 'this'. (This happens because the >>> dependent base B<T> of C<T> doesn't have a binfo object, so it appears >>> to DERIVED_FROM_P that A is not an indirect base of C<T>.) From there >>> we create the corresponding deferred access check, which we then >>> perform at instantiation time and which (unsurprisingly) fails. >>> >>> The problem ultimately seems to be that we can't, in general, know >>> whether a use of a scoped non-static member goes through 'this' until >>> instantiation time, as the second testcase below demonstrates. So this >>> patch makes check_accessibility_of_qualified_id punt in this situation. >>> >>> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK to >>> commit? >>> >>> gcc/cp/ChangeLog: >>> >>> PR c++/98515 >>> * semantics.c (check_accessibility_of_qualified_id): Punt if >>> we're checking the access of a scoped non-static member at >>> class template parse time. >>> >>> gcc/testsuite/ChangeLog: >>> >>> PR c++/98515 >>> * g++.dg/template/access32.C: New test. >>> * g++.dg/template/access33.C: New test. >>> --- >>> gcc/cp/semantics.c | 20 +++++++++++++++----- >>> gcc/testsuite/g++.dg/template/access32.C | 8 ++++++++ >>> gcc/testsuite/g++.dg/template/access33.C | 9 +++++++++ >>> 3 files changed, 32 insertions(+), 5 deletions(-) >>> create mode 100644 gcc/testsuite/g++.dg/template/access32.C >>> create mode 100644 gcc/testsuite/g++.dg/template/access33.C >>> >>> diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c >>> index b448efe024a..f52b2e4d1e7 100644 >>> --- a/gcc/cp/semantics.c >>> +++ b/gcc/cp/semantics.c >>> @@ -2107,14 +2107,24 @@ check_accessibility_of_qualified_id (tree decl, >>> /* If the reference is to a non-static member of the >>> current class, treat it as if it were referenced through >>> `this'. */ >>> - tree ct; >>> if (DECL_NONSTATIC_MEMBER_P (decl) >>> - && current_class_ptr >>> - && DERIVED_FROM_P (scope, ct = current_nonlambda_class_type ())) >>> - qualifying_type = ct; >>> + && current_class_ptr) >>> + { >>> + if (dependent_type_p (TREE_TYPE (current_class_ptr))) >> >> This should also look at current_nonlambda_class_type. > > Ah, ack. But it seems to me we really only need to be checking > dependence of current_nonlambda_class_type here. Yes, that's what I meant, sorry about the ambiguous use of "also". :) > IIUC, dependence of > these two types should coincide except in the case where we're inside a > generic lambda within a non-template class (in which case > current_class_ptr will dependent and current_nonlambda_class_type won't). > But in this case we have enough information to be able to resolve the > access check at parse time, I think (and so we shouldn't punt). > > The below patch, which seems to pass 'make check-c++', checks the > dependence of current_nonlambda_class_type instead of that of > current_class_ptr. Does this approach seem right? OK. > -- >8 -- > > Subject: [PATCH] c++: Fix access checking of scoped non-static member > [PR98515] > > In the first testcase below, we incorrectly reject the use of the > protected non-static member A::var0 from C<int>::g() because > check_accessibility_of_qualified_id, at template parse time, determines > that the access doesn't go through 'this'. (This happens because the > dependent base B<T> of C<T> doesn't have a binfo object, so it appears > to DERIVED_FROM_P that A is not an indirect base of C<T>.) From there > we create the corresponding deferred access check, which we then > perform at instantiation time and which (unsurprisingly) fails. > > The problem ultimately seems to be that we can't in general determine > whether a use of a scoped non-static member goes through 'this' until > instantiation time, as the second testcase below illustrates. So this > patch makes check_accessibility_of_qualified_id punt in such situations > to avoid creating a bogus deferred access check. > > gcc/cp/ChangeLog: > > PR c++/98515 > * semantics.c (check_accessibility_of_qualified_id): Punt if > we're checking access of a scoped non-static member inside a > class template. > > gcc/testsuite/ChangeLog: > > PR c++/98515 > * g++.dg/template/access32.C: New test. > * g++.dg/template/access33.C: New test. > --- > gcc/cp/semantics.c | 22 +++++++++++++++++----- > gcc/testsuite/g++.dg/template/access32.C | 8 ++++++++ > gcc/testsuite/g++.dg/template/access33.C | 9 +++++++++ > 3 files changed, 34 insertions(+), 5 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/template/access32.C > create mode 100644 gcc/testsuite/g++.dg/template/access33.C > > diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c > index b448efe024a..51f7c114b03 100644 > --- a/gcc/cp/semantics.c > +++ b/gcc/cp/semantics.c > @@ -2107,14 +2107,26 @@ check_accessibility_of_qualified_id (tree decl, > /* If the reference is to a non-static member of the > current class, treat it as if it were referenced through > `this'. */ > - tree ct; > if (DECL_NONSTATIC_MEMBER_P (decl) > - && current_class_ptr > - && DERIVED_FROM_P (scope, ct = current_nonlambda_class_type ())) > - qualifying_type = ct; > + && current_class_ptr) > + { > + if (tree current = current_nonlambda_class_type ()) > + { > + if (dependent_type_p (current)) > + /* In general we can't know whether this access goes through > + `this' until instantiation time. Punt now, or else we might > + create a deferred access check that's not relative to 'this' > + when it ought to be. We'll check this access again after > + substitution, e.g. from tsubst_qualified_id. */ > + return true; > + > + if (DERIVED_FROM_P (scope, current)) > + qualifying_type = current; > + } > + } > /* Otherwise, use the type indicated by the > nested-name-specifier. */ > - else > + if (!qualifying_type) > qualifying_type = nested_name_specifier; > } > else > diff --git a/gcc/testsuite/g++.dg/template/access32.C b/gcc/testsuite/g++.dg/template/access32.C > new file mode 100644 > index 00000000000..08faa9f0f97 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/template/access32.C > @@ -0,0 +1,8 @@ > +// PR c++/98515 > +// { dg-do compile } > + > +struct A { protected: int var0; }; > +template <class> struct B : public A { }; > +template <class T> struct C : public B<T> { void g(); }; > +template <class T> void C<T>::g() { A::var0++; } > +template class C<int>; > diff --git a/gcc/testsuite/g++.dg/template/access33.C b/gcc/testsuite/g++.dg/template/access33.C > new file mode 100644 > index 00000000000..9fb9b9a1236 > --- /dev/null > +++ b/gcc/testsuite/g++.dg/template/access33.C > @@ -0,0 +1,9 @@ > +// PR c++/98515 > +// { dg-do compile } > + > +struct A { protected: int var0; }; > +template <class> struct B : public A { }; > +template <class T> struct C : public B<T> { void g(); }; > +template <class T> void C<T>::g() { A::var0++; } // { dg-error "protected|invalid" } > +template <> struct B<char> { }; > +template class C<char>; > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] c++: Fix access checking of scoped non-static member [PR98515] 2021-01-08 1:12 ` Jason Merrill @ 2021-01-08 15:39 ` Patrick Palka 0 siblings, 0 replies; 5+ messages in thread From: Patrick Palka @ 2021-01-08 15:39 UTC (permalink / raw) To: Jason Merrill; +Cc: Patrick Palka, gcc-patches On Thu, 7 Jan 2021, Jason Merrill wrote: > On 1/7/21 5:47 PM, Patrick Palka wrote: > > On Thu, 7 Jan 2021, Jason Merrill wrote: > > > > > On 1/6/21 1:19 PM, Patrick Palka wrote: > > > > In the first testcase below, we incorrectly reject the use of the > > > > protected non-static member A::var0 from C<int>::g() because > > > > check_accessibility_of_qualified_id, at template parse time, determines > > > > that the access doesn't go through 'this'. (This happens because the > > > > dependent base B<T> of C<T> doesn't have a binfo object, so it appears > > > > to DERIVED_FROM_P that A is not an indirect base of C<T>.) From there > > > > we create the corresponding deferred access check, which we then > > > > perform at instantiation time and which (unsurprisingly) fails. > > > > > > > > The problem ultimately seems to be that we can't, in general, know > > > > whether a use of a scoped non-static member goes through 'this' until > > > > instantiation time, as the second testcase below demonstrates. So this > > > > patch makes check_accessibility_of_qualified_id punt in this situation. > > > > > > > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK to > > > > commit? > > > > > > > > gcc/cp/ChangeLog: > > > > > > > > PR c++/98515 > > > > * semantics.c (check_accessibility_of_qualified_id): Punt if > > > > we're checking the access of a scoped non-static member at > > > > class template parse time. > > > > > > > > gcc/testsuite/ChangeLog: > > > > > > > > PR c++/98515 > > > > * g++.dg/template/access32.C: New test. > > > > * g++.dg/template/access33.C: New test. > > > > --- > > > > gcc/cp/semantics.c | 20 +++++++++++++++----- > > > > gcc/testsuite/g++.dg/template/access32.C | 8 ++++++++ > > > > gcc/testsuite/g++.dg/template/access33.C | 9 +++++++++ > > > > 3 files changed, 32 insertions(+), 5 deletions(-) > > > > create mode 100644 gcc/testsuite/g++.dg/template/access32.C > > > > create mode 100644 gcc/testsuite/g++.dg/template/access33.C > > > > > > > > diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c > > > > index b448efe024a..f52b2e4d1e7 100644 > > > > --- a/gcc/cp/semantics.c > > > > +++ b/gcc/cp/semantics.c > > > > @@ -2107,14 +2107,24 @@ check_accessibility_of_qualified_id (tree decl, > > > > /* If the reference is to a non-static member of the > > > > current class, treat it as if it were referenced through > > > > `this'. */ > > > > - tree ct; > > > > if (DECL_NONSTATIC_MEMBER_P (decl) > > > > - && current_class_ptr > > > > - && DERIVED_FROM_P (scope, ct = current_nonlambda_class_type ())) > > > > - qualifying_type = ct; > > > > + && current_class_ptr) > > > > + { > > > > + if (dependent_type_p (TREE_TYPE (current_class_ptr))) > > > > > > This should also look at current_nonlambda_class_type. > > > > Ah, ack. But it seems to me we really only need to be checking > > dependence of current_nonlambda_class_type here. > > Yes, that's what I meant, sorry about the ambiguous use of "also". :) Oops, I see what you had meant now, sorry about the confusion :) > > > IIUC, dependence of > > these two types should coincide except in the case where we're inside a > > generic lambda within a non-template class (in which case > > current_class_ptr will dependent and current_nonlambda_class_type won't). > > But in this case we have enough information to be able to resolve the > > access check at parse time, I think (and so we shouldn't punt). > > > > The below patch, which seems to pass 'make check-c++', checks the > > dependence of current_nonlambda_class_type instead of that of > > current_class_ptr. Does this approach seem right? > > OK. Thanks. > > > -- >8 -- > > > > Subject: [PATCH] c++: Fix access checking of scoped non-static member > > [PR98515] > > > > In the first testcase below, we incorrectly reject the use of the > > protected non-static member A::var0 from C<int>::g() because > > check_accessibility_of_qualified_id, at template parse time, determines > > that the access doesn't go through 'this'. (This happens because the > > dependent base B<T> of C<T> doesn't have a binfo object, so it appears > > to DERIVED_FROM_P that A is not an indirect base of C<T>.) From there > > we create the corresponding deferred access check, which we then > > perform at instantiation time and which (unsurprisingly) fails. > > > > The problem ultimately seems to be that we can't in general determine > > whether a use of a scoped non-static member goes through 'this' until > > instantiation time, as the second testcase below illustrates. So this > > patch makes check_accessibility_of_qualified_id punt in such situations > > to avoid creating a bogus deferred access check. > > > > gcc/cp/ChangeLog: > > > > PR c++/98515 > > * semantics.c (check_accessibility_of_qualified_id): Punt if > > we're checking access of a scoped non-static member inside a > > class template. > > > > gcc/testsuite/ChangeLog: > > > > PR c++/98515 > > * g++.dg/template/access32.C: New test. > > * g++.dg/template/access33.C: New test. > > --- > > gcc/cp/semantics.c | 22 +++++++++++++++++----- > > gcc/testsuite/g++.dg/template/access32.C | 8 ++++++++ > > gcc/testsuite/g++.dg/template/access33.C | 9 +++++++++ > > 3 files changed, 34 insertions(+), 5 deletions(-) > > create mode 100644 gcc/testsuite/g++.dg/template/access32.C > > create mode 100644 gcc/testsuite/g++.dg/template/access33.C > > > > diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c > > index b448efe024a..51f7c114b03 100644 > > --- a/gcc/cp/semantics.c > > +++ b/gcc/cp/semantics.c > > @@ -2107,14 +2107,26 @@ check_accessibility_of_qualified_id (tree decl, > > /* If the reference is to a non-static member of the > > current class, treat it as if it were referenced through > > `this'. */ > > - tree ct; > > if (DECL_NONSTATIC_MEMBER_P (decl) > > - && current_class_ptr > > - && DERIVED_FROM_P (scope, ct = current_nonlambda_class_type ())) > > - qualifying_type = ct; > > + && current_class_ptr) > > + { > > + if (tree current = current_nonlambda_class_type ()) > > + { > > + if (dependent_type_p (current)) > > + /* In general we can't know whether this access goes through > > + `this' until instantiation time. Punt now, or else we might > > + create a deferred access check that's not relative to 'this' > > + when it ought to be. We'll check this access again after > > + substitution, e.g. from tsubst_qualified_id. */ > > + return true; > > + > > + if (DERIVED_FROM_P (scope, current)) > > + qualifying_type = current; > > + } > > + } > > /* Otherwise, use the type indicated by the > > nested-name-specifier. */ > > - else > > + if (!qualifying_type) > > qualifying_type = nested_name_specifier; > > } > > else > > diff --git a/gcc/testsuite/g++.dg/template/access32.C > > b/gcc/testsuite/g++.dg/template/access32.C > > new file mode 100644 > > index 00000000000..08faa9f0f97 > > --- /dev/null > > +++ b/gcc/testsuite/g++.dg/template/access32.C > > @@ -0,0 +1,8 @@ > > +// PR c++/98515 > > +// { dg-do compile } > > + > > +struct A { protected: int var0; }; > > +template <class> struct B : public A { }; > > +template <class T> struct C : public B<T> { void g(); }; > > +template <class T> void C<T>::g() { A::var0++; } > > +template class C<int>; > > diff --git a/gcc/testsuite/g++.dg/template/access33.C > > b/gcc/testsuite/g++.dg/template/access33.C > > new file mode 100644 > > index 00000000000..9fb9b9a1236 > > --- /dev/null > > +++ b/gcc/testsuite/g++.dg/template/access33.C > > @@ -0,0 +1,9 @@ > > +// PR c++/98515 > > +// { dg-do compile } > > + > > +struct A { protected: int var0; }; > > +template <class> struct B : public A { }; > > +template <class T> struct C : public B<T> { void g(); }; > > +template <class T> void C<T>::g() { A::var0++; } // { dg-error > > "protected|invalid" } > > +template <> struct B<char> { }; > > +template class C<char>; > > > > ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-01-08 15:39 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-01-06 18:19 [PATCH] c++: Fix access checking of scoped non-static member [PR98515] Patrick Palka 2021-01-07 21:37 ` Jason Merrill 2021-01-07 22:47 ` Patrick Palka 2021-01-08 1:12 ` Jason Merrill 2021-01-08 15:39 ` Patrick Palka
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).