12 Overloading [over]

12.5 Built-in operators [over.built]

The candidate operator functions that represent the built-in operators defined in [expr.compound] are specified in this subclause.

These candidate functions participate in the operator overload resolution process as described in [over.match.oper] and are used for no other purpose.

[Note 1:

Because built-in operators take only operands with non-class type, and operator overload resolution occurs only when an operand expression originally has class or enumeration type, operator overload resolution can resolve to a built-in operator only when an operand has a class type that has a user-defined conversion to a non-class type appropriate for the operator, or when an operand has an enumeration type that can be converted to a type appropriate for the operator.

Also note that some of the candidate operator functions given in this subclause are more permissive than the built-in operators themselves.

As described in [over.match.oper], after a built-in operator is selected by overload resolution the expression is subject to the requirements for the built-in operator given in [expr.compound], and therefore to any additional semantic constraints given there.

In some cases, user-written candidates with the same name and parameter types as a built-in candidate operator function cause the built-in operator function to not be included in the set of candidate functions.

— end note]

In this subclause, the term promoted integral type is used to refer to those cv-unqualified integral types which are preserved by integral promotion (including e.g. int and long but excluding e.g. char).

[Note 2:

In all cases where a promoted integral type is required, an operand of unscoped enumeration type will be acceptable by way of the integral promotions.

— end note]

In the remainder of this subclause, vq represents either volatile or no cv-qualifier.

For every pair (T, vq), where T is a cv-unqualified arithmetic type other than bool or a cv-unqualified pointer to (possibly cv-qualified) object type, there exist candidate operator functions of the form vq T& operator++(vq T&); T operator++(vq T&, int); vq T& operator--(vq T&); T operator--(vq T&, int);

For every (possibly cv-qualified) object type T and for every function type T that has neither cv-qualifiers nor a ref-qualifier, there exist candidate operator functions of the form T& operator*(T*);

For every type T there exist candidate operator functions of the form T* operator+(T*);

For every cv-unqualified floating-point or promoted integral type T, there exist candidate operator functions of the form T operator+(T); T operator-(T);

For every promoted integral type T, there exist candidate operator functions of the form T operator~(T);

For every quintuple (C1, C2, T, cv1, cv2), where C2 is a class type, C1 is the same type as C2 or is a derived class of C2, and T is an object type or a function type, there exist candidate operator functions of the form cv12 T& operator->*(cv1 C1*, cv2 T C2::*); where cv12 is the union of cv1 and cv2.

The return type is shown for exposition only; see [expr.mptr.oper] for the determination of the operator's result type.

For every pair of types L and R, where each of L and R is a floating-point or promoted integral type, there exist candidate operator functions of the form LR operator*(L, R); LR operator/(L, R); LR operator+(L, R); LR operator-(L, R); bool operator==(L, R); bool operator!=(L, R); bool operator<(L, R); bool operator>(L, R); bool operator<=(L, R); bool operator>=(L, R); where LR is the result of the usual arithmetic conversions ([expr.arith.conv]) between types L and R.

For every integral type T there exists a candidate operator function of the form std::strong_ordering operator<=>(T, T);

For every pair of floating-point types L and R, there exists a candidate operator function of the form std::partial_ordering operator<=>(L, R);

For every cv-qualified or cv-unqualified object type T there exist candidate operator functions of the form T* operator+(T*, std::ptrdiff_t); T& operator[](T*, std::ptrdiff_t); T* operator-(T*, std::ptrdiff_t); T* operator+(std::ptrdiff_t, T*); T& operator[](std::ptrdiff_t, T*);

For every T, where T is a pointer to object type, there exist candidate operator functions of the form std::ptrdiff_t operator-(T, T);

For every T, where T is an enumeration type or a pointer type, there exist candidate operator functions of the form bool operator==(T, T); bool operator!=(T, T); bool operator<(T, T); bool operator>(T, T); bool operator<=(T, T); bool operator>=(T, T); R operator<=>(T, T); where R is the result type specified in [expr.spaceship].

For every T, where T is a pointer-to-member type or std::nullptr_t, there exist candidate operator functions of the form bool operator==(T, T); bool operator!=(T, T);

For every pair of promoted integral types L and R, there exist candidate operator functions of the form LR operator%(L, R); LR operator&(L, R); LR operator^(L, R); LR operator|(L, R); L operator<<(L, R); L operator>>(L, R); where LR is the result of the usual arithmetic conversions ([expr.arith.conv]) between types L and R.

For every triple (L, vq, R), where L is an arithmetic type, and R is a floating-point or promoted integral type, there exist candidate operator functions of the form vq L& operator=(vq L&, R); vq L& operator*=(vq L&, R); vq L& operator/=(vq L&, R); vq L& operator+=(vq L&, R); vq L& operator-=(vq L&, R);

For every pair (T, vq), where T is any type, there exist candidate operator functions of the form T*vq& operator=(T*vq&, T*);

For every pair (T, vq), where T is an enumeration or pointer-to-member type, there exist candidate operator functions of the form vq T& operator=(vq T&, T);

For every pair (T, vq), where T is a cv-qualified or cv-unqualified object type, there exist candidate operator functions of the form T*vq& operator+=(T*vq&, std::ptrdiff_t); T*vq& operator-=(T*vq&, std::ptrdiff_t);

For every triple (L, vq, R), where L is an integral type, and R is a promoted integral type, there exist candidate operator functions of the form vq L& operator%=(vq L&, R); vq L& operator<<=(vq L&, R); vq L& operator>>=(vq L&, R); vq L& operator&=(vq L&, R); vq L& operator^=(vq L&, R); vq L& operator|=(vq L&, R);

There also exist candidate operator functions of the form bool operator!(bool); bool operator&&(bool, bool); bool operator||(bool, bool);

For every pair of types L and R, where each of L and R is a floating-point or promoted integral type, there exist candidate operator functions of the form LR operator?:(bool, L, R); where LR is the result of the usual arithmetic conversions ([expr.arith.conv]) between types L and R.

[Note 3:

As with all these descriptions of candidate functions, this declaration serves only to describe the built-in operator for purposes of overload resolution.

The operator “?:” cannot be overloaded.

— end note]

For every type T, where T is a pointer, pointer-to-member, or scoped enumeration type, there exist candidate operator functions of the form T operator?:(bool, T, T);