[namespace.constraints] (original) (raw)

16.4.5.2.1 Namespace std [namespace.std]

Unless otherwise specified, the behavior of a C++ program is undefined if it adds declarations or definitions to namespacestdor to a namespace within namespacestd.

Unless explicitly prohibited, a program may add a template specialization for any standard library class template to namespacestd provided that

• the added declaration depends on at least one program-defined type, and
• the specialization meets the standard library requirements for the original template.155

The behavior of a C++ program is undefined if it declares an explicit or partial specialization of any standard library variable template, except where explicitly permitted by the specification of that variable template.

[Note 1:

The requirements on an explicit or partial specialization are stated by each variable template that grants such permission.

— _end note_]

The behavior of a C++ program is undefined if it declares

• an explicit specialization of any member function of a standard library class template, or
• an explicit specialization of any member function template of a standard library class or class template, or
• an explicit or partial specialization of any member class template of a standard library class or class template, or
• a deduction guide for any standard library class template.

A program may explicitly instantiate a class template defined in the standard library only if the declaration

• depends on the name of at least one program-defined type, and
• the instantiation meets the standard library requirements for the original template.

Let F denote a standard library function ([global.functions]), a standard library static member function, or an instantiation of a standard library function template.

Unless F is designated an addressable function, the behavior of a C++ program is unspecified (possibly ill-formed) if it explicitly or implicitly attempts to form a pointer to F.

Moreover, the behavior of a C++ program is unspecified (possibly ill-formed) if it attempts to form a reference to _F_or if it attempts to form a pointer-to-member designating either a standard library non-static member function ([member.functions]) or an instantiation of a standard library member function template.

A translation unit shall not declare namespace std to be an inline namespace ([namespace.def]).