Reproduce special members table

Question

I have the following (well known) table:

Can I test it by using type_traits?

I wrote:

class CSpecialMethods
{
public:
//	CSpecialMethods() {}
// 	CSpecialMethods(bool) {}
//	CSpecialMethods(const CSpecialMethods& rhs) {}
	CSpecialMethods& operator=(const CSpecialMethods& rhs) {} // declare user copy assignment operator, nothing else
//	CSpecialMethods(CSpecialMethods&& rhs) {}
//	CSpecialMethods& operator=(CSpecialMethods&& rhs) {}
//	~CSpecialMethods() {}
};

and

	std::clog << "constructors:" << std::endl;
	std::clog << std::is_trivially_default_constructible_v<CSpecialMethods> << std::endl;
	std::clog << std::is_trivially_constructible_v<CSpecialMethods> << std::endl;
	std::clog << "copy methods:" << std::endl;
	std::clog << std::is_trivially_copy_constructible_v<CSpecialMethods> << std::endl;
	std::clog << std::is_trivially_copy_assignable_v<CSpecialMethods> << std::endl;
	std::clog << "move methods:" << std::endl;
	std::clog << std::is_trivially_move_constructible_v<CSpecialMethods> << std::endl;
	std::clog << std::is_trivially_move_assignable_v<CSpecialMethods> << std::endl;
	std::clog << "destructor:" << std::endl;
	std::clog << std::is_trivially_destructible_v<CSpecialMethods> << std::endl;

but the outcome does not reflect the table:

constructors:

1

1

copy methods:

1

0

move methods:

1

0

destructor:

1

So, can I reproduce that special members table using type_traits?

If I write:

class CSpecialMethods
{
public:
//	CSpecialMethods() {}
// 	CSpecialMethods(bool) {}
	CSpecialMethods(const CSpecialMethods& rhs) = default;
	CSpecialMethods& operator=(const CSpecialMethods& rhs) {}
//	CSpecialMethods(CSpecialMethods&& rhs) {}
//	CSpecialMethods& operator=(CSpecialMethods&& rhs) {}
//	~CSpecialMethods() {}
};

I got:

constructors:

0

0

copy methods:

1

0

move methods:

1

0

destructor:

1

Quite different then other sample, but still, doesn't reflect the top table ...

Answer 1

Hi,

After my test,

~CSpecialMethods() {} or =default are different results.

In addition, from the doc:

the class Ty has no virtual functions

So type_traits is not reliable.

Best regards,

Minxin Yu

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