Some functions described in this Clause are specified to throw exceptions of type system_error. Such exceptions shall be thrown if any of the function's error conditions is detected or a call to an operating system or other underlying API results in an error that prevents the library function from meeting its specifications. Failure to allocate storage shall be reported as described in [res.on.exception.handling].
[ Example: Consider a function in this clause that is specified to throw exceptions of type system_error and specifies error conditions that include operation_not_permitted for a thread that does not have the privilege to perform the operation. Assume that, during the execution of this function, an errno of EPERM is reported by a POSIX API call used by the implementation. Since POSIX specifies an errno of EPERM when “the caller does not have the privilege to perform the operation”, the implementation maps EPERM to an error_condition of operation_not_permitted ([syserr]) and an exception of type system_error is thrown. — end example ]