20 Library introduction [library]

20.5 Library-wide requirements [requirements]

20.5.4 Constraints on programs [constraints]

20.5.4.1 Overview [constraints.overview]

Subclause [constraints] describes restrictions on C++ programs that use the facilities of the C++ standard library.
The following subclauses specify constraints on the program's use of namespaces, its use of various reserved names, its use of headers, its use of standard library classes as base classes ([derived.classes]), its definitions of replacement functions, and its installation of handler functions during execution.