C++ named requirements: TriviallyCopyable (since C++11)

Note: the standard doesn't define a named requirement with this name. This is a type category defined by the core language. It is included here as a named requirement only for consistency.

Requirements

The following types are collectively called trivially copyable types :

• scalar types
• trivially copyable class types
• arrays of such types
• cv-qualified versions of these types

Notes

In general, for any trivially copyable type T and an object obj1 of T , the underlying bytes of obj1 can be copied into an array of char , or unsigned char , or std::byte (since C++17) or into obj2 , a distinct object of T . Neither obj1 nor obj2 may be a potentially-overlapping subobject.

If the underlying bytes of obj1 are copied into such an array, and then the resulting content is copied back into obj1 , obj1 will hold its original value. If the underlying bytes of obj1 are copied into obj2 , obj2 will hold obj1 's value.

Underlying bytes can be copied by std::memcpy or std::memmove , as long as no living volatile object is accessed.

Defect reports

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

DR	Applied to	Behavior as published	Correct behavior
CWG 1734	C++11	C++03 POD with deleted non-trivial assignment was not trivial	deleted ctors/operators allowed
CWG 2094	C++11	Volatile scalar types are not trivially copyable ( CWG 1746 )	made trivially copyable

See also

is_trivially_copyable (C++11)

checks if a type is trivially copyable (class template)