C++ named requirements: StandardLayoutType

 

C++

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C++ named requirements

Basic
DefaultConstructible CopyAssignable CopyConstructible	MoveAssignable (C++11) MoveConstructible (C++11) Destructible
Type properties
ScalarType TriviallyCopyable (C++11) StandardLayoutType (C++11)	PODType TrivialType (C++11) ImplicitLifetimeType (C++20)
Library-Wide
EqualityComparable LessThanComparable Swappable (C++11) ValueSwappable (C++11) NullablePointer (C++11) Hash (C++11)	Allocator FunctionObject Callable Predicate BinaryPredicate Compare
Container
Container SequenceContainer ContiguousContainer (C++17) ReversibleContainer	AssociativeContainer AllocatorAwareContainer UnorderedAssociativeContainer (C++11)
Container Elements
DefaultInsertable (C++11) CopyInsertable (C++11) MoveInsertable (C++11)	EmplaceConstructible (C++11) Erasable (C++11)
Iterator
LegacyIterator LegacyOutputIterator LegacyInputIterator LegacyForwardIterator	LegacyBidirectionalIterator LegacyRandomAccessIterator LegacyContiguousIterator (C++17) ConstexprIterator (C++20)
Stream I/O
FormattedInputFunction UnformattedInputFunction	FormattedOutputFunction UnformattedOutputFunction
Formatting
BasicFormatter (C++20)	Formatter (C++20)
Random Numbers
SeedSequence (C++11) RandomNumberEngine (C++11)	RandomNumberDistribution (C++11) UniformRandomBitGenerator (C++11) RandomNumberEngineAdaptor (C++11)
Concurrency
BasicLockable (C++11) Lockable (C++11) TimedLockable (C++11) SharedLockable (C++14) SharedTimedLockable (C++14)	Mutex (C++11) TimedMutex (C++11) SharedMutex (C++17) SharedTimedMutex (C++14)
Other
CharTraits RegexTraits (C++11) BitmaskType NumericType LiteralType (C++11)	UnaryTypeTrait (C++11) BinaryTypeTrait (C++11) TransformationTrait (C++11) Clock (C++11) TrivialClock (C++11)

 

Specifies that a type is a standard layout type. Standard layout types are useful for communicating with code written in other programming languages.

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 standard-layout types:

• scalar types
• standard-layout class types
• arrays of such types
• cv-qualified versions of these types

Properties

See Standard layout.

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 1672	C++11	first non-static data member rule ignored existence of empty base classes	first non-static data member rule made recursive
CWG 1813	C++11	class with a member defined in an indirect base wasn't technically standard-layout	all member declarations must be in the same class
CWG 2120	C++11	array as first member wasn't considered when comparing the first element type with type of a base	array members are considered

See also

is_standard_layout (C++11)

checks if a type is a standard-layout type (class template)