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Showing content from https://en.cppreference.com/w/cpp/algorithm/../types/is_destructible.html below:

std::is_destructible, std::is_trivially_destructible, std::is_nothrow_destructible - cppreference.com

template< class T > struct is_destructible;

(1) (since C++11)

template< class T > struct is_trivially_destructible;

(2) (since C++11)

template< class T > struct is_nothrow_destructible;

(3) (since C++11)

1) If T is a reference type, provides the member constant value equal to true.

If T is (possibly cv-qualified) void, a function type, or an array of unknown bound, value equals false.

T

is an object type, then, for the type

U

that is

std::remove_all_extents<T>::type

, if the expression

std::declval<U&>().~U()

is well-formed in unevaluated context,

value

equals

true

. Otherwise,

value

equals

false

3) Same as (1), but the destructor is noexcept.

If T is not a complete type, (possibly cv-qualified) void, or an array of unknown bound, the behavior is undefined.

If an instantiation of a template above depends, directly or indirectly, on an incomplete type, and that instantiation could yield a different result if that type were hypothetically completed, the behavior is undefined.

If the program adds specializations for any of the templates described on this page, the behavior is undefined.

[edit] Helper variable templates

template< class T > constexpr bool is_destructible_v = is_destructible<T>::value;

(since C++17)

template< class T > constexpr bool is_trivially_destructible_v = is_trivially_destructible<T>::value;

(since C++17)

template< class T > constexpr bool is_nothrow_destructible_v = is_nothrow_destructible<T>::value;

(since C++17) Inherited from std::integral_constant Member constants true if T is destructible, false otherwise
(public static member constant) Member functions converts the object to bool, returns value
(public member function) returns value
(public member function) Member types [edit] Notes

Because the C++ program terminates if a destructor throws an exception during stack unwinding (which usually cannot be predicted), all practical destructors are non-throwing even if they are not declared noexcept. All destructors found in the C++ standard library are non-throwing.

Storage occupied by trivially destructible objects may be reused without calling the destructor.

[edit] Possible implementation [edit] Example

#include <iostream>
#include <string>
#include <type_traits>
 
struct Foo
{
    std::string str;
    ~Foo() noexcept {};
};
 
struct Bar
{
    ~Bar() = default;
};
 
static_assert(std::is_destructible<std::string>::value == true);
static_assert(std::is_trivially_destructible_v<Foo> == false);
static_assert(std::is_nothrow_destructible<Foo>() == true);
static_assert(std::is_trivially_destructible<Bar>{} == true);
 
int main() {}

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior LWG 2049 C++11 the specification was incompletable because of the imaginary wrapping struct made complete [edit] See also

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