On Thu, Jul 29, 2021 at 09:50:10AM +0200, Jakub Jelinek via Gcc-patches wrote:
> Now that I'm writing the above text and rereading the
> pointer-interconvertibility definition, I think my
> first_nonstatic_data_member_p
> and fold_builtin_is_pointer_inverconvertible_with_class have one bug,
> for unions the pointer inter-convertibility doesn't talk about std layout at
> all, so I think I need to check for std_layout_type_p only for non-union
> class types and accept any union, std_layout_type_p or not. But when
> recursing from a union type into anonymous structure type punt if the
> anonymous structure type is not std_layout_type_p + add testcase coverage.
For this part, here is an incremental fix. Tested on x86_64-linux.
It also shows that in the case (we're beyond the standard in this case
because anonymous structures are not in the standard) of union with
non-std-layout anonymous structure in it, in the case in the testcases like:
struct D {};
struct E { [[no_unique_address]] D e; };
union Y { int a; struct : public E { short b; long c; }; long long d; };
the builtin will return false for &Y::b - while &Y::b is at offset zero,
the anonymous structure is not std-layout and therefore the
pointer-interconvertibility rules say pointers aren't interconvertible.
But in case like:
union Y2 { int a; struct : public E { int b; long c; }; long long d; };
it will return true for &Y2::b - while the same applies, there is
another union member with int type. In theory when seeing the PTRMEM_CST
we could still differentiate, &Y2::a is ok but &Y2::b is not. But as soon
as we have just an INTEGER_CST with OFFSET_TYPE or need to check it at
runtime, all we know is that we have pointer to int data member in Y2
at offset 0, and that is the same for &Y2::a and &Y2::b.
2021-07-29 Jakub Jelinek <ja...@redhat.com>
PR c++/101539
* semantics.c (first_nonstatic_data_member_p): Don't recurse into
non-std-layout non-union class types from union type.
(fold_builtin_is_pointer_inverconvertible_with_class): Don't check
std-layout type for union types.
* g++.dg/cpp2a/is-pointer-interconvertible-with-class1.C: Add
tests for non-std-layout union type.
* g++.dg/cpp2a/is-pointer-interconvertible-with-class2.C: Likewise.
* g++.dg/cpp2a/is-pointer-interconvertible-with-class4.C: Add
tests for non-std-layout anonymous class type in union.
* g++.dg/cpp2a/is-pointer-interconvertible-with-class5.C: Likewise.
--- gcc/cp/semantics.c.jj 2021-07-28 23:06:38.665443459 +0200
+++ gcc/cp/semantics.c 2021-07-29 15:44:30.659713391 +0200
@@ -10631,7 +10631,9 @@ first_nonstatic_data_member_p (tree type
if (TREE_CODE (type) != UNION_TYPE)
return first_nonstatic_data_member_p (TREE_TYPE (field),
membertype);
- if (first_nonstatic_data_member_p (TREE_TYPE (field), membertype))
+ if ((TREE_CODE (TREE_TYPE (field)) == UNION_TYPE
+ || std_layout_type_p (TREE_TYPE (field)))
+ && first_nonstatic_data_member_p (TREE_TYPE (field), membertype))
return true;
}
else if (TREE_CODE (type) != UNION_TYPE)
@@ -10677,7 +10679,8 @@ fold_builtin_is_pointer_inverconvertible
if (!complete_type_or_else (basetype, NULL_TREE))
return boolean_false_node;
- if (!std_layout_type_p (basetype))
+ if (TREE_CODE (basetype) != UNION_TYPE
+ && !std_layout_type_p (basetype))
return boolean_false_node;
if (!first_nonstatic_data_member_p (basetype, membertype))
--- gcc/testsuite/g++.dg/cpp2a/is-pointer-interconvertible-with-class1.C.jj
2021-07-28 23:06:38.667443431 +0200
+++ gcc/testsuite/g++.dg/cpp2a/is-pointer-interconvertible-with-class1.C
2021-07-29 15:46:55.809743808 +0200
@@ -28,6 +28,7 @@ union U { int a; double b; long long c;
struct V { union { int a; long b; }; int c; };
union X { int a; union { short b; long c; }; long long d; };
struct Y { void foo () {} };
+union Z { int a; private: int b; protected: int c; public: int d; };
static_assert (std::is_pointer_interconvertible_with_class (&B::b));
static_assert (!std::is_pointer_interconvertible_with_class (&B::b2));
@@ -60,3 +61,5 @@ static_assert (std::is_pointer_interconv
static_assert (std::is_pointer_interconvertible_with_class (&X::d));
static_assert (!std::is_pointer_interconvertible_with_class ((int B::*)
nullptr));
static_assert (!std::is_pointer_interconvertible_with_class (&Y::foo));
+static_assert (std::is_pointer_interconvertible_with_class (&Z::a));
+static_assert (std::is_pointer_interconvertible_with_class (&Z::d));
--- gcc/testsuite/g++.dg/cpp2a/is-pointer-interconvertible-with-class2.C.jj
2021-07-28 23:06:38.667443431 +0200
+++ gcc/testsuite/g++.dg/cpp2a/is-pointer-interconvertible-with-class2.C
2021-07-29 15:48:33.075423974 +0200
@@ -28,6 +28,7 @@ union U { int a; double b; long long c;
struct V { union { int a; long b; }; int c; };
union X { int a; union { short b; long c; }; long long d; };
struct Y { void foo () {} };
+union Z { int a; private: int b; protected: int c; public: int d; };
int
main ()
@@ -125,4 +126,10 @@ main ()
auto t31 = &Y::foo;
if (std::is_pointer_interconvertible_with_class (t31))
__builtin_abort ();
+ auto t32 = &Z::a;
+ if (!std::is_pointer_interconvertible_with_class (t32))
+ __builtin_abort ();
+ auto t33 = &Z::d;
+ if (!std::is_pointer_interconvertible_with_class (t33))
+ __builtin_abort ();
}
--- gcc/testsuite/g++.dg/cpp2a/is-pointer-interconvertible-with-class4.C.jj
2021-07-28 23:06:38.667443431 +0200
+++ gcc/testsuite/g++.dg/cpp2a/is-pointer-interconvertible-with-class4.C
2021-07-29 15:56:54.340622140 +0200
@@ -14,6 +14,9 @@ is_pointer_interconvertible_with_class (
struct W { struct { int a; long b; }; int c; };
union X { int a; struct { short b; long c; }; long long d; };
+struct D {};
+struct E { [[no_unique_address]] D e; };
+union Y { int a; struct : public E { short b; long c; }; long long d; };
static_assert (std::is_pointer_interconvertible_with_class (&W::a));
static_assert (!std::is_pointer_interconvertible_with_class (&W::b));
@@ -22,3 +25,7 @@ static_assert (std::is_pointer_interconv
static_assert (std::is_pointer_interconvertible_with_class (&X::b));
static_assert (!std::is_pointer_interconvertible_with_class (&X::c));
static_assert (std::is_pointer_interconvertible_with_class (&X::d));
+static_assert (std::is_pointer_interconvertible_with_class (&Y::a));
+static_assert (!std::is_pointer_interconvertible_with_class (&Y::b));
+static_assert (!std::is_pointer_interconvertible_with_class (&Y::c));
+static_assert (std::is_pointer_interconvertible_with_class (&Y::d));
--- gcc/testsuite/g++.dg/cpp2a/is-pointer-interconvertible-with-class5.C.jj
2021-07-28 23:06:38.667443431 +0200
+++ gcc/testsuite/g++.dg/cpp2a/is-pointer-interconvertible-with-class5.C
2021-07-29 15:57:10.829398399 +0200
@@ -14,6 +14,9 @@ is_pointer_interconvertible_with_class (
struct W { struct { int a; long b; }; int c; };
union X { int a; struct { short b; long c; }; long long d; };
+struct D {};
+struct E { [[no_unique_address]] D e; };
+union Y { int a; struct : public E { short b; long c; }; long long d; };
int
main ()
@@ -39,4 +42,16 @@ main ()
auto t7 = &X::d;
if (!std::is_pointer_interconvertible_with_class (t7))
__builtin_abort ();
+ auto t8 = &Y::a;
+ if (!std::is_pointer_interconvertible_with_class (t8))
+ __builtin_abort ();
+ auto t9 = &Y::b;
+ if (std::is_pointer_interconvertible_with_class (t9))
+ __builtin_abort ();
+ auto t10 = &Y::c;
+ if (std::is_pointer_interconvertible_with_class (t10))
+ __builtin_abort ();
+ auto t11 = &Y::d;
+ if (!std::is_pointer_interconvertible_with_class (t11))
+ __builtin_abort ();
}
Jakub
