std::is_trivially_copyable
Defined in header <type_traits> |
||
---|---|---|
template< class T > struct is_trivially_copyable; |
(since C++11) |
If T
is a trivially copyable type, provides the member constant value
equal to true
. For any other type, value
is false
.
The behavior is undefined if std::remove_all_extents_t<T>
is an incomplete type and not (possibly cv-qualified) void
.
The behavior of a program that adds specializations for is_trivially_copyable
or is_trivially_copyable_v
(since C++17) is undefined.
Template parameters
T | - | a type to check |
Helper variable template
template< class T > inline constexpr bool is_trivially_copyable_v = is_trivially_copyable<T>::value; |
(since C++17) |
Inherited from std::integral_constant
Member constants
value
[static]
|
true if T is a trivially copyable type , false otherwise (public static member constant) |
Member functions
operator bool
|
converts the object to bool , returns value (public member function) |
operator()
(C++14)
|
returns value (public member function) |
Member types
Type | Definition |
---|---|
value_type |
bool |
type |
std::integral_constant<bool, value> |
Notes
Objects of trivially-copyable types that are not potentially-overlapping subobjects are the only C++ objects that may be safely copied with std::memcpy
or serialized to/from binary files with std::ofstream::write()
/std::ifstream::read()
.
Example
#include <iostream> #include <type_traits> struct A { int m; }; struct B { B(B const&) {} }; struct C { virtual void foo(); }; struct D { int m; D(D const&) = default; // -> trivially copyable D(int x): m(x+1) {} }; int main() { std::cout << std::boolalpha; std::cout << std::is_trivially_copyable<A>::value << '\n'; std::cout << std::is_trivially_copyable<B>::value << '\n'; std::cout << std::is_trivially_copyable<C>::value << '\n'; std::cout << std::is_trivially_copyable<D>::value << '\n'; }
Output:
true false false true
See also
(C++11)
|
checks if a type is trivial (class template) |
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