15 Library introduction [library]

15.3 Definitions [definitions]

15.3.22 replacement function [defns.replacement]

non-reserved function whose definition is provided by a C++ program
[Note
:
Only one definition for such a function is in effect for the duration of the program's execution, as the result of creating the program ([lex.phases]) and resolving the definitions of all translation units ([basic.link]).
end note
]