What does "cv-unqualified" mean in C++?
There are fundamental types and compound types. Fundamental types are the arithmetic types,
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
- volatile-qualified - with the
- const-volatile-qualified - with both the
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
A type is "cv-unqualified" if it doesn't have any cv-qualifiers. A cv-qualifer is either
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
constspecifier in a decl-specifier-seq declares an object of const-qualified object type; such object is called a
The presence of a
volatilespecifier in a decl-specifier-seq declares an object of volatilequalified object type; such object is called a
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.