Terminology: "indirection" versus "dereference" (revision 2)

This paper addresses core issue 342 and implements a consistent terminology for "indirection through a pointer" throughout the core language section of the standard. As decided in Bloomington, the term "dereference" would be replaced by "indirection". This paper reflects the additional comments made during review at the Kona meeting. Due to the volume of the changes, they are presented as a separate paper as opposed to integrating them into the core issues list.

• 5.3.1 expr.unary.op paragraph 1
• 8.3.4 dcl.array paragraph 8
• 8.3.5 dcl.fct paragraph 9
• 20.4.7.4 lib.meta.trans.pt

... The effect of dereferencing indirecting through a pointer returned as a request for zero size is undefined. [ Footnote: ... ]

• the value returned by a call to the C++ standard library implementation of ::operator new(std::size_t); [ Footnote: This section does not impose restrictions on dereferencing indirection through pointers to memory not allocated by ::operator new. This maintains the ability of many C++ implementations to use binary libraries and components written in other languages. In particular, this applies to C binaries, because dereferencing indirection through pointers to memory allocated by malloc std::malloc is not restricted. ]
• the result of taking the address of an object (or one of its subobjects) designated by an lvalue resulting from dereferencing indirection through a safely-derived pointer value;
• ...

... Indirection through such Such a pointer may be dereferenced is permitted but the resulting lvalue may only be used in limited ways, as described below. The program has undefined behavior if:

• ...

... Since the result has type "pointer to member of D of type cv T", it can be dereferenced indirection through it with a D object is valid. The result is the same as if indirecting through the pointer to member of B were dereferenced with the B subobject of D. The null member pointer value is converted to the null member pointer value of the destination type. [ Footnote: ... ]

... [ Note: although class B need not contain the original member, the dynamic type of the object on with which indirection through the pointer to member is performed dereferenced must contain the original member; see 5.5 expr.mptr.oper. -- end note ]

... [ Note: indirection through a pointer to an incomplete type (other than cv void) is valid can be dereferenced. ... ]

... Otherwise they compare equal if and only if they would refer to the same member of the same most derived object (1.8 intro.object) or the same subobject if they were dereferenced indirection with a hypothetical object of the associated class type were performed. [ Example: ... ]

[ Note: Because the language linkage is part of a function type, when indirecting through a pointer to C function (for example) is dereferenced, the function to which it the resulting lvalue refers is considered a C function. -- end note ]

... [ Note: in particular, a null reference cannot exist in a well-defined program, because the only way to create such a reference would be to bind it to the "object" obtained by dereferencing indirection through a null pointer, which causes undefined behavior. As described in 9.6 class.bit, a reference cannot be bound directly to a bit-field. ]

Change in 17.6.3.5 allocator.requirements table 27:

a dereferenceable pointer of type C* through which indirection is valid

Returns: The first member function returns a dereferenceable pointer to r obtained by calling Ptr::pointer_to(r) through which indirection is valid; an instantiation of this function is ill-formed if Ptr does not have a matching pointer_to static member function. The second member function returns std::addressof(r).

... Hence indirection through a pointer pointers located there may not be dereferenced is undefined if the object they point it points to was created by global operator new and not previously declared reachable. [ Note: ... ]

... In all of the following algorithms, the formal template parameter ForwardIterator is required to satisfy the requirements of a forward iterator (24.2.5 forward.iterators), and is required to have the property that no exceptions are thrown from increment, assignment, comparison, or dereference of indirection through valid iterators. ...

Requires: t shall be dereferenceable point to an object.

Requires: If the iterator's dereference indirection operator returns an lvalue or a const rvalue pair<key_type, mapped_type>, then both key_type and mapped_type shall be CopyConstructible.

Requires: If the iterator's dereference indirection operator returns an lvalue or a const rvalue pair<key_type, mapped_type>, then both key_type and mapped_type shall be CopyConstructible.

Requires If the iterator's dereference indirection operator returns an lvalue or a non-const rvalue, then Key shall be CopyConstructible.

Requires If the iterator's dereference indirection operator returns an lvalue or a non-const rvalue, then Key shall be CopyConstructible.

Class template move_iterator is an iterator adaptor with the same behavior as the underlying iterator except that its dereference indirection operator implicitly converts the value returned by the underlying iterator's dereference indirection operator to an rvalue reference. ....

regex_iterator dereference indirection

regex_token_iterator dereference indirection