Common types

In order to use data and functions in C and C++, they must have the same or comparable types. C++ contains the same set of basic data types as C; however, since C++ is a true superset of C, it also contains more types than C.

The following C++ types may be used for linkage between C++ and other languages:

• fundamental types: char, short, int, long, long long, float, double, long double, void

• qualifiers: unsigned, const, volatile

• pointers to common types

• arrays of common types (passed as pointers)

• structures and unions
  These must not contain the following components in C++: member functions, constructors, destructors, base classes, and access specifiers. The structure and union components must have common types, i.e. must be syntactically identical.

• simple enumerations

• functions with common argument and result types
  Ellipses (...) are permitted.

The following types must not be used if linkage to other languages is required:

• reference types

• pointers to members of classes, unions, or structures

• classes

• structures and unions containing member functions, constructors, destructors, base classes, or access specifiers

• enumerations with explicit type or scope: enum E1 : int; enum struct E2;
• types defined locally in a class

• member functions

• templates

• std::nullptr_t
• bool
• _Complex, _Imaginary (a C11 feature)
• varable length arrays (a C11 feature)