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PR libstdc++/90220 Fix std::any_cast for array types

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Although the std::any constructors use decay_t to determine the type of
the contained value, std::any_cast should use the un-decayed type (and
so always fail for function and array types that decay to pointers).

Using remove_cv_t is correct, because the condition for std::any_cast
to return non-null is operand.type() == typeid(T) and typeid ignores
top-level cv-qualifiers.

	PR libstdc++/90220
	* include/std/any (__any_caster): Use remove_cv_t instead of decay_t.
	Avoid a runtime check for types that can never be stored in std::any.
	* testsuite/20_util/any/misc/any_cast.cc: Test std::any_cast with
	array types.

From-SVN: r270547
This commit is contained in:
Jonathan Wakely 2019-04-24 16:17:43 +01:00 committed by Jonathan Wakely
parent 540bc8a8b1
commit 92750002ef
3 changed files with 38 additions and 7 deletions
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6
libstdc++-v3/ChangeLog
View File

@ -1,5 +1,11 @@
2019-04-24 Jonathan Wakely <jwakely@redhat.com>
PR libstdc++/90220
* include/std/any (__any_caster): Use remove_cv_t instead of decay_t.
Avoid a runtime check for types that can never be stored in std::any.
* testsuite/20_util/any/misc/any_cast.cc: Test std::any_cast with
array types.
PR libstdc++/90220 (partial)
* include/std/any (any_cast<T>(any*), any_cast<T>(const any*)): Do
not attempt ill-formed static_cast to pointers to non-object types.

22
libstdc++-v3/include/std/any
View File

@ -506,14 +506,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _Tp>
void* __any_caster(const any* __any)
{
if constexpr (is_copy_constructible_v<decay_t<_Tp>>)
// any_cast<T> returns non-null if __any->type() == typeid(T) and
// typeid(T) ignores cv-qualifiers so remove them:
using _Up = remove_cv_t<_Tp>;
// The contained value has a decayed type, so if decay_t<U> is not U,
// then it's not possible to have a contained value of type U:
if constexpr (!is_same_v<decay_t<_Up>, _Up>)
return nullptr;
// Only copy constructible types can be used for contained values:
else if constexpr (!is_copy_constructible_v<_Up>)
return nullptr;
// This check is equivalent to __any->type() == typeid(_Tp)
else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage)
{
if (__any->_M_manager == &any::_Manager<decay_t<_Tp>>::_S_manage)
{
any::_Arg __arg;
__any->_M_manager(any::_Op_access, __any, &__arg);
return __arg._M_obj;
}
any::_Arg __arg;
__any->_M_manager(any::_Op_access, __any, &__arg);
return __arg._M_obj;
}
return nullptr;
}

17
libstdc++-v3/testsuite/20_util/any/misc/any_cast.cc
View File

@ -154,6 +154,22 @@ void test06()
}
}
void test07()
{
int arr[3];
any a(arr);
VERIFY( a.type() == typeid(int*) ); // contained value is decayed
int (*p1)[3] = any_cast<int[3]>(&a);
VERIFY( a.type() != typeid(int[3]) ); // so any_cast should return nullptr
VERIFY( p1 == nullptr );
int (*p2)[] = any_cast<int[]>(&a);
VERIFY( a.type() != typeid(int[]) ); // so any_cast should return nullptr
VERIFY( p2 == nullptr );
const int (*p3)[] = any_cast<int[]>(&std::as_const(a));
VERIFY( p3 == nullptr );
}
int main()
{
test01();
@ -162,4 +178,5 @@ int main()
test04();
test05();
test06();
test07();
}