16 Library introduction [library]

16.4 Library-wide requirements [requirements]

16.4.2 Library contents and organization [organization]

16.4.2.2 Library contents [contents]

1
#
The C++ standard library provides definitions for the entities and macros described in the synopses of the C++ standard library headers ([headers]), unless otherwise specified.
2
#
All library entities except operator new and operator delete are defined within the namespace std or namespaces nested within namespace std.¹³¹
It is unspecified whether names declared in a specific namespace are declared directly in that namespace or in an inline namespace inside that namespace.¹³²
3
#
Whenever an unqualified name other than swap, make_error_code, make_error_condition, from_stream, or submdspan_mapping is used in the specification of a declaration D in [support] through [exec] or [depr], its meaning is established as-if by performing unqualified name lookup ([basic.lookup.unqual]) in the context of D.
[Note 1: 
Argument-dependent lookup is not performed.
— end note]
Similarly, the meaning of a qualified-id is established as-if by performing qualified name lookup ([basic.lookup.qual]) in the context of D.
[Example 1: 
The reference to is_array_v in the specification of std​::​to_array ([array.creation]) refers to ​::​std​::​is_array_v.
— end example]
[Note 2: 
Operators in expressions ([over.match.oper]) are not so constrained; see [global.functions].
— end note]
The meaning of the unqualified name swap is established in an overload resolution context for swappable values ([swappable.requirements]).
The meanings of the unqualified names make_error_code, make_error_condition, from_stream, and submdspan_mapping are established as-if by performing argument-dependent lookup ([basic.lookup.argdep]).
131)131)
The C standard library headers ([support.c.headers]) also define names within the global namespace, while the C++ headers for C library facilities ([headers]) can also define names within the global namespace.
132)132)
This gives implementers freedom to use inline namespaces to support multiple configurations of the library.