19 Diagnostics library [diagnostics]

19.5 System error support [syserr]

19.5.1 General [syserr.general]

Subclause [syserr] describes components that the standard library and C++ programs may use to report error conditions originating from the operating system or other low-level application program interfaces.
Components described in [syserr] shall not change the value of errno ([errno]).
Implementations should leave the error states provided by other libraries unchanged.