16 Library introduction [library]

16.3 Method of description [description]

16.3.3 Other conventions [conventions]

16.3.3.6 Freestanding items [freestanding.item]

1
#
A freestanding item is a declaration, entity, typedef-name, or macro that is required to be present in a freestanding implementation and a hosted implementation.
2
#
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.
3
#
Function declarations and function template declarations followed by a comment that include freestanding-deleted are freestanding deleted functions.
On freestanding implementations, it is implementation-defined whether each entity introduced by a freestanding deleted function is a deleted function ([dcl.fct.def.delete]) or whether the requirements are the same as the corresponding requirements for a hosted implementation.
[Note 1: 
Deleted definitions reduce the chance of overload resolution silently changing when migrating from a freestanding implementation to a hosted implementation.
— end note]
[Example 1: double abs(double j); // freestanding-deleted — end example]
4
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A declaration in a synopsis is a freestanding item if
  • (4.1)
    it is followed by a comment that includes freestanding,
  • (4.2)
    it is followed by a comment that includes freestanding-deleted, or
  • (4.3)
    the header synopsis begins with a comment that includes freestanding and the declaration is not followed by a comment that includes hosted.
    [Note 2: 
    Declarations followed by hosted in freestanding headers are not freestanding items.
    As a result, looking up the name of such functions can vary between hosted and freestanding implementations.
    — end note]
[Example 2: // all freestanding namespace std { — end example]
5
#
An entity, deduction guide, or typedef-name is a freestanding item if it is:
  • (5.1)
    introduced by a declaration that is a freestanding item,
  • (5.2)
    a member of a freestanding item other than a namespace,
  • (5.3)
    an enumerator of a freestanding item,
  • (5.4)
    a deduction guide of a freestanding item,
  • (5.5)
    an enclosing namespace of a freestanding item,
  • (5.6)
    a friend of a freestanding item,
  • (5.7)
    denoted by a typedef-name that is a freestanding item, or
  • (5.8)
    denoted by an alias template that is a freestanding item.
6
#
A macro is a freestanding item if it is defined in a header synopsis and
  • (6.1)
    the definition is followed by a comment that includes freestanding, or
  • (6.2)
    the header synopsis begins with a comment that includes freestanding and the definition is not followed by a comment that includes hosted.
[Example 3: #define NULL see below // freestanding — end example]
7
#
[Note 3: 
Freestanding annotations follow some additional exposition conventions that do not impose any additional normative requirements.
Header synopses that begin with a comment containing "all freestanding" contain no hosted items and no freestanding deleted functions.
Header synopses that begin with a comment containing "mostly freestanding" contain at least one hosted item or freestanding deleted function.
Classes and class templates followed by a comment containing "partially freestanding" contain at least one hosted item or freestanding deleted function.
— end note]
[Example 4: template<class T, size_t N> struct array; // partially freestanding template<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-deleted constexpr const_reference at(size_type n) const; // freestanding-deleted }; — end example]