Type support (basic types, RTTI, type traits)
< cpp
(See also type for type system overview)
Basic types
Fundamental types defined by the language
Additional basic types and macros
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Defined in header
<cstddef> |
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Defined in header
<stddef.h> |
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| unsigned integer type returned by the sizeof operator (typedef) |
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| signed integer type returned when subtracting two pointers (typedef) |
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(C++11)
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the type of the null pointer literal nullptr (typedef) |
| implementation-defined null pointer constant (macro constant) |
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(C++11)
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trivial type with alignment requirement as great as any other scalar type (typedef) |
| byte offset from the beginning of a standard-layout type to specified member (function macro) |
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Defined in header
<cstddef> |
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(C++17)
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the byte type (enum) |
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Defined in header
<stdbool.h> |
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__bool_true_false_are_defined
(C++11)
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C compatibility macro constant, expands to integer literal 1 (macro constant) |
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Defined in header
<stdalign.h> |
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__alignas_is_defined
(C++11)
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C compatibility macro constant, expands to integer literal 1 (macro constant) |
Fixed width integer types (since C++11)
Numeric limits
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Defined in header
<limits> |
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| provides an interface to query properties of all fundamental numeric types. (class template) |
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C numeric limits interface
Runtime type identification
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Defined in header
<typeinfo> |
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| contains some type's information, generated by the implementation. This is the class returned by the typeid operator. (class) |
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| exception that is thrown if an argument in a typeid expression is null (class) |
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| exception that is thrown by an invalid dynamic_cast expression, i.e. a cast of reference type fails (class) |
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Defined in header
<typeindex> |
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(C++11)
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wrapper around a type_info object, that can be used as index in associative and unordered associative containers(class) |
Type traits (since C++11)
Type traits defines a compile-time template-based interface to query or modify the properties of types.
Attempting to specialize a template defined in the <type_traits> header results in undefined behavior, except that std::common_type may be specialized as described in its description.
A template defined in the <type_traits> header may be instantiated with an incomplete type unless otherwise specified, notwithstanding the general prohibition against instantiating standard library templates with incomplete types.
Type properties
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Defined in header
<type_traits> |
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Primary type categories |
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(C++11)
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checks if a type is void (class template) |
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(C++14)
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checks if a type is std::nullptr_t (class template) |
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(C++11)
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checks if a type is an integral type (class template) |
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(C++11)
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checks if a type is a floating-point type (class template) |
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(C++11)
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checks if a type is an array type (class template) |
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(C++11)
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checks if a type is an enumeration type (class template) |
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(C++11)
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checks if a type is an union type (class template) |
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(C++11)
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checks if a type is a non-union class type (class template) |
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(C++11)
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checks if a type is a function type (class template) |
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(C++11)
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checks if a type is a pointer type (class template) |
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(C++11)
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checks if a type is a lvalue reference (class template) |
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(C++11)
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checks if a type is a rvalue reference (class template) |
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(C++11)
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checks if a type is a pointer to a non-static member object (class template) |
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(C++11)
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checks if a type is a pointer to a non-static member function (class template) |
Composite type categories |
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(C++11)
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checks if a type is a fundamental type (class template) |
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(C++11)
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checks if a type is an arithmetic type (class template) |
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(C++11)
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checks if a type is a scalar type (class template) |
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(C++11)
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checks if a type is an object type (class template) |
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(C++11)
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checks if a type is a compound type (class template) |
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(C++11)
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checks if a type is either a lvalue reference or rvalue reference (class template) |
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(C++11)
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checks if a type is a pointer to an non-static member function or object (class template) |
Type properties |
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(C++11)
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checks if a type is const-qualified (class template) |
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(C++11)
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checks if a type is volatile-qualified (class template) |
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(C++11)
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checks if a type is trivial (class template) |
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(C++11)
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checks if a type is trivially copyable (class template) |
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(C++11)
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checks if a type is a standard-layout type (class template) |
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(C++11)(deprecated in C++20)
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checks if a type is a plain-old data (POD) type (class template) |
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(C++11)(deprecated in C++17)(removed in C++20)
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checks if a type is a literal type (class template) |
| checks if every bit in the type's object representation contributes to its value (class template) |
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(C++11)
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checks if a type is a class (but not union) type and has no non-static data members (class template) |
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(C++11)
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checks if a type is a polymorphic class type (class template) |
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(C++11)
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checks if a type is an abstract class type (class template) |
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(C++14)
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checks if a type is a final class type (class template) |
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(C++17)
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checks if a type is an aggregate type (class template) |
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(C++11)
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checks if a type is a signed arithmetic type (class template) |
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(C++11)
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checks if a type is an unsigned arithmetic type (class template) |
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(C++20)
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checks if a type is an array type of known bound (class template) |
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(C++20)
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checks if a type is an array type of unknown bound (class template) |
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(C++23)
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checks if a type is a scoped enumeration type (class template) |
Supported operations |
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(C++11)(C++11)(C++11)
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checks if a type has a constructor for specific arguments (class template) |
| checks if a type has a default constructor (class template) |
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(C++11)(C++11)(C++11)
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checks if a type has a copy constructor (class template) |
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(C++11)(C++11)(C++11)
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checks if a type can be constructed from an rvalue reference (class template) |
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(C++11)(C++11)(C++11)
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checks if a type has a assignment operator for a specific argument (class template) |
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(C++11)(C++11)(C++11)
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checks if a type has a copy assignment operator (class template) |
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(C++11)(C++11)(C++11)
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checks if a type has a move assignment operator (class template) |
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(C++11)(C++11)(C++11)
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checks if a type has a non-deleted destructor (class template) |
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(C++11)
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checks if a type has a virtual destructor (class template) |
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(C++17)(C++17)(C++17)(C++17)
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checks if objects of a type can be swapped with objects of same or different type (class template) |
Property queries |
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(C++11)
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obtains the type's alignment requirements (class template) |
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(C++11)
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obtains the number of dimensions of an array type (class template) |
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(C++11)
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obtains the size of an array type along a specified dimension (class template) |
Type relationships |
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(C++11)
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checks if two types are the same (class template) |
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(C++11)
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checks if a type is derived from the other type (class template) |
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(C++11)(C++20)
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checks if a type can be converted to the other type (class template) |
| checks if a type can be invoked (as if by std::invoke) with the given argument types (class template) |
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(C++20)
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checks if two types are layout-compatible (class template) |
| checks if a type is a pointer-interconvertible (initial) base of another type (class template) |
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| checks if objects of a type are pointer-interconvertible with the specified subobject of that type (function template) |
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(C++20)
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checks if two specified members correspond to each other in the common initial subsequence of two specified types (function template) |
Other |
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(C++20)
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detects whether the call occurs within a constant-evaluated context (function) |
Type modifications
Type modification templates create new type definitions by applying modifications on a template parameter. The resulting type can then be accessed through type member typedef.
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Defined in header
<type_traits> |
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Const-volatility specifiers |
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(C++11)(C++11)(C++11)
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removes const or/and volatile specifiers from the given type (class template) |
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(C++11)(C++11)(C++11)
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adds const or/and volatile specifiers to the given type (class template) |
References |
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(C++11)
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removes a reference from the given type (class template) |
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(C++11)(C++11)
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adds a lvalue or rvalue reference to the given type (class template) |
Pointers |
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(C++11)
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removes a pointer from the given type (class template) |
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(C++11)
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adds a pointer to the given type (class template) |
Sign modifiers |
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(C++11)
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makes the given integral type signed (class template) |
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(C++11)
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makes the given integral type unsigned (class template) |
Arrays |
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(C++11)
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removes one extent from the given array type (class template) |
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(C++11)
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removes all extents from the given array type (class template) |
Miscellaneous transformations
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Defined in header
<type_traits> |
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(C++11)
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defines the type suitable for use as uninitialized storage for types of given size (class template) |
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(C++11)
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defines the type suitable for use as uninitialized storage for all given types (class template) |
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(C++11)
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applies type transformations as when passing a function argument by value (class template) |
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(C++20)
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combines std::remove_cv and std::remove_reference (class template) |
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(C++11)
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conditionally removes a function overload or template specialization from overload resolution (class template) |
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(C++11)
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chooses one type or another based on compile-time boolean (class template) |
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(C++11)
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determines the common type of a group of types (class template) |
| determines the common reference type of a group of types (class template) |
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(C++11)
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obtains the underlying integer type for a given enumeration type (class template) |
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(C++11)(removed in C++20)(C++17)
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deduces the result type of invoking a callable object with a set of arguments (class template) |
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(C++17)
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void variadic alias template (alias template) |
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(C++20)
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returns the type argument unchanged (class template) |
Operations on traits
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Defined in header
<type_traits> |
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(C++17)
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variadic logical AND metafunction (class template) |
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(C++17)
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variadic logical OR metafunction (class template) |
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(C++17)
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logical NOT metafunction (class template) |
Helper classes
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Defined in header
<type_traits> |
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(C++11)(C++17)
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compile-time constant of specified type with specified value (class template) |
Two specializations of std::integral_constant for the type bool are provided:
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Defined in header
<type_traits> |
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Specializations |
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| Type | Definition |
true_type |
std::integral_constant<bool, true> |
false_type |
std::integral_constant<bool, false> |