[expr.type] (original) (raw)

7 Expressions [expr]

7.2 Properties of expressions [expr.prop]

7.2.2 Type [expr.type]

If an expression initially has the type “reference toT” ([dcl.ref], [dcl.init.ref]), the type is adjusted toT prior to any further analysis; the value category of the expression is not altered.

Let X be the object or function denoted by the reference.

If a pointer to X would be valid in the context of the evaluation of the expression ([basic.fundamental]), the result designates X; otherwise, the behavior is undefined.

[Note 1:

Before the lifetime of the reference has started or after it has ended, the behavior is undefined (see [basic.life]).

— _end note_]

If a prvalue initially has the type “cv T”, whereT is a cv-unqualified non-class, non-array type, the type of the expression is adjusted to T prior to any further analysis.

The composite pointer type of two operands p1 andp2 having types T1 and T2, respectively, where at least one is a pointer or pointer-to-member type orstd​::​nullptr_t, is:

• if both p1 and p2 are null pointer constants,std​::​nullptr_t;
• if either p1 or p2 is a null pointer constant, T2 or T1, respectively;
• if T1 or T2 is “pointer to cv1 void” and the other type is “pointer to cv2 T”, where T is an object type or void, “pointer to cv12 void”, where cv12 is the union of cv1 and cv2;
• if T1 or T2 is “pointer to noexcept function” and the other type is “pointer to function”, where the function types are otherwise the same, “pointer to function”;
• if T1 is “pointer to C1” and T2 is “pointer toC2”, where C1 is reference-related to C2 or C2 is reference-related to C1 ([dcl.init.ref]), the qualification-combined type ([conv.qual]) of T1 and T2 or the qualification-combined type of T2 and T1, respectively;
• if T1 or T2 is “pointer to member of C1 of type function”, the other type is “pointer to member of C2 of type noexcept function”, andC1 is reference-related to C2 orC2 is reference-related to C1 ([dcl.init.ref]), where the function types are otherwise the same, “pointer to member of C2 of type function” or “pointer to member of C1 of type function”, respectively;
• if T1 is “pointer to member of C1 of type cv1 U” andT2 is “pointer to member of C2 of type cv2 U”, for some non-function type U, where C1 is reference-related to C2 or C2 is reference-related toC1 ([dcl.init.ref]), the qualification-combined type of T2 and T1 or the qualification-combined type of T1 and T2, respectively;
• if T1 and T2 are similar types ([conv.qual]), the qualification-combined type of T1 andT2;
• otherwise, a program that necessitates the determination of a composite pointer type is ill-formed.

[Example 1: typedef void *p;typedef const int *q;typedef int **pi;typedef const int **pci;

The composite pointer type of p and q is “pointer to const void”; the composite pointer type of pi and pci is “pointer to const pointer toconst int”.

— _end example_]