Annex C (informative) Compatibility [diff]

C.2 C++ and ISO C++ 2014 [diff.cpp14]

C.2.8 [library]: library introduction [diff.cpp14.library]

1
#
Affected subclause: [headers]
Change: New headers.

Rationale: New functionality.

Effect on original feature: The following C++ headers are new: <any>, <charconv>, <execution>, <filesystem>, <memory_­resource>, <optional>,
Valid C++ 2014 code that #includes headers with these names may be invalid in this revision of C++.
2
#
Affected subclause: [namespace.future]
Change: New reserved namespaces.

Rationale: Reserve namespaces for future revisions of the standard library that might otherwise be incompatible with existing programs.

Effect on original feature: The global namespaces std followed by an arbitrary sequence of digits ([lex.name]) are reserved for future standardization.
Valid C++ 2014 code that uses such a top-level namespace, e.g., std2, may be invalid in this revision of C++.