I'm so confused about this template I wrote, It's supposed to 'auto' deduce a pointer type that I pass in, but the compiler doesn't seem to think that two types are the same, whereas I do, and typeid()
is on my side.
#include <iostream>
template <auto* static_ptr_to_object>
struct Handle
{
// static_ptr_to_object should be a pointer to a Whale<char>
// Both of the following typedefs should result in types of Whale<char>
// When I cout typeid() of these types it prints out the same types
// However std::is_same_v returns false
using pointee_type1 = std::remove_pointer_t<decltype(static_ptr_to_object)>;
using pointee_type2 = decltype(*static_ptr_to_object); // The two are the same types
void showTypes()
{
//static_assert(std::is_same_v<pointee_type1, pointee_type2>);
// Uncommenting this line will make the static assert fail
std::cout << "Type of 'pointee_type1' = " << typeid(pointee_type1).name() << "\n";
std::cout << "Type of 'pointee_type2' = " << typeid(pointee_type2).name() << "\n";
if (typeid(pointee_type1) == typeid(pointee_type2))
std::cout << "Types are the same\n";
else std::cout << "Types are not the same\n";
}
bool b1 = std::is_integral_v<decltype(pointee_type1::member)>;
// Uncommenting the below line will make compilation fail
//bool b2 = std::is_integral_v<decltype(pointee_type2::member)>;
// pointee_type2 must be a class or namespace when followed by ::
// pointee_type2 left of '::' must be a class or namespace name
};
template <typename T>
struct Whale
{
T member;
};
Whale<char> whale;
int main()
{
Handle<&whale> handleToWhale;
handleToWhale.showTypes();
}
So I think the two types are the same, and typeid()
operator says they are the same, yet std::is_same
returns false
, and based on the compiler error message it doesn't recognise that pointee_type2
is a class type because it doesn't recognise the :: operator for it.
Edit: My understanding about dereferencing pointers was wrong, this question relates to how a pointer dereference will return a reference type in some cases.
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