What does "cv-unqualified" mean in C++?

There are fundamental types and compound types. Fundamental types are the arithmetic types, void, and std::nullptr_t. Compound types are arrays, functions, pointers, references, classes, unions, enumerations, and pointers to non-static members.

A cv-unqualified type is any of those types.

For any cv-unqualified type, there are three corresponding cv-qualified types:

  • const-qualified - with the const cv-qualifier
  • volatile-qualified - with the volatile cv-qualifier
  • const-volatile-qualified - with both the const and volatile cv-qualifiers

Note, however, that cv-qualifiers applied to an array type actually apply to its elements.

The cv-qualified and cv-unqualified types are distinct. That is int is a distinct type from const int.

A type is "cv-unqualified" if it doesn't have any cv-qualifiers. A cv-qualifer is either const or volatile.

cv-unqualified type is a type that hasn't been specified by any of cv-qualifiers. These define two basic properties of a type: constness and volatility. See C++03 3.9.3 CV-qualifiers §1:

A type mentioned in 3.9.1 and 3.9.2 is a cv-unqualified type. Each type which is a cv-unqualified complete or incomplete object type or is void (3.9) has three corresponding cv-qualified versions of its type:

  • a const-qualified version,
  • a volatile-qualified version, and
  • a const-volatile-qualified version.

The term object type (1.8) includes the cv-qualifiers specified when the object is created.

The presence of a const specifier in a decl-specifier-seq declares an object of const-qualified object type; such object is called a const object.

The presence of a volatile specifier in a decl-specifier-seq declares an object of volatilequalified object type; such object is called a volatile object.

The presence of both cv-qualifiers in a declspecifier-seq declares an object of const-volatile-qualified object type; such object is called a const volatile object.



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