[freestanding.item]

# 16 Library introduction [[library]](./#library)

## 16.3 Method of description [[description]](description#freestanding.item)

### 16.3.3 Other conventions [[conventions]](conventions#freestanding.item)

#### 16.3.3.7 Freestanding items [freestanding.item]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L968)

A [*freestanding item*](#def:freestanding_item "16.3.3.7 Freestanding items [freestanding.item]") is
a declaration, entity, [*typedef-name*](dcl.typedef#nt:typedef-name "9.2.4 The typedef specifier [dcl.typedef]"), or macro
that is required to be present in
a freestanding implementation and a hosted implementation[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L975)

Unless otherwise specified,
the requirements on freestanding items for a freestanding implementation
are the same as the corresponding requirements for a hosted implementation,
except that not all of the members of those items are required to be present[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L981)

Function declarations and function template declarations
followed by a comment that include *freestanding-deleted* are[*freestanding deleted functions*](#def:function,freestanding_deleted "16.3.3.7 Freestanding items [freestanding.item]")[.](#3.sentence-1)

On freestanding implementations,
it is implementation-defined
whether each entity introduced by a freestanding deleted function
is a deleted function ([[dcl.fct.def.delete]](dcl.fct.def.delete "9.6.3 Deleted definitions")) or
whether the requirements are the same as
the corresponding requirements for a hosted implementation[.](#3.sentence-2)

[*Note [1](#note-1)*:

Deleted definitions reduce the chance of overload resolution silently changing
when migrating from a freestanding implementation to a hosted implementation[.](#3.sentence-3)

— *end note*]

[*Example [1](#example-1)*: double abs(double j); // freestanding-deleted — *end example*]

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L1001)

A declaration in a synopsis is a freestanding item if

- [(4.1)](#4.1)

it is followed by a comment that includes *freestanding*,

- [(4.2)](#4.2)

it is followed by a comment that includes *freestanding-deleted*, or

- [(4.3)](#4.3)

the header synopsis begins with a comment
that includes *freestanding* and
the declaration is not followed by a comment that includes *hosted*[.](#4.sentence-1)
  [*Note [2](#note-2)*:
  Declarations followed by *hosted* in freestanding headers are
not freestanding items[.](#4.3.sentence-2)
  As a result, looking up the name of such functions can vary
between hosted and freestanding implementations[.](#4.3.sentence-3)
 — *end note*]

[*Example [2](#example-2)*: // all freestandingnamespace std { — *end example*]

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L1024)

An entity, deduction guide, or [*typedef-name*](dcl.typedef#nt:typedef-name "9.2.4 The typedef specifier [dcl.typedef]") is a freestanding item if its introducing declaration is not followed by
a comment that includes *hosted*, and is:

- [(5.1)](#5.1)

introduced by a declaration that is a freestanding item,

- [(5.2)](#5.2)

a member of a freestanding item other than a namespace,

- [(5.3)](#5.3)

an enumerator of a freestanding item,

- [(5.4)](#5.4)

a deduction guide of a freestanding item,

- [(5.5)](#5.5)

an enclosing namespace of a freestanding item,

- [(5.6)](#5.6)

a friend of a freestanding item,

- [(5.7)](#5.7)

denoted by a [*typedef-name*](dcl.typedef#nt:typedef-name "9.2.4 The typedef specifier [dcl.typedef]") that is a freestanding item, or

- [(5.8)](#5.8)

denoted by an alias template that is a freestanding item[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L1042)

A macro is a freestanding item if it is defined in a header synopsis and

- [(6.1)](#6.1)

the definition is followed by a comment
that includes *freestanding*, or

- [(6.2)](#6.2)

the header synopsis begins with a comment
that includes *freestanding* and
the definition is not followed by a comment that includes *hosted*[.](#6.sentence-1)

[*Example [3](#example-3)*: #define NULL *see below* // freestanding — *end example*]

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L1058)

[*Note [3](#note-3)*:

Freestanding annotations follow some additional exposition conventions
that do not impose any additional normative requirements[.](#7.sentence-1)

Header synopses that begin with a comment containing "all freestanding"
contain no hosted items and no freestanding deleted functions[.](#7.sentence-2)

Header synopses that begin with a comment containing "mostly freestanding"
contain at least one hosted item or freestanding deleted function[.](#7.sentence-3)

Classes and class templates followed by a comment
containing "partially freestanding"
contain at least one hosted item or freestanding deleted function[.](#7.sentence-4)

— *end note*]

[*Example [4](#example-4)*: template<class T, size_t N> struct array; // partially freestandingtemplate<class T, size_t N>struct array {constexpr reference operator[](size_type n); constexpr const_reference operator[](size_type n) const; constexpr reference at(size_type n); // freestanding-deletedconstexpr const_reference at(size_type n) const; // freestanding-deleted}; — *end example*]