ANSIC_error & OS_error &c

[Sam S. <sd...@gn...>]

Hi,
Right now all OS errors are reported as simple-os-errors with a format
string and an argument list.
This is not good because for automated error recovery one has to parse
the error message to distinguish between, say, EPERM and ENOENT.
Thus I want to add a $CODE slot to OS-ERROR which would contain the
error code (symbolic, converted by check_errno_reverse in the syscalls
module).
However, once we start keeping the error code slot in the condition
object, there is no good reason for os-error to be a simple-error
because we can now do
    (define-condition os-error (error)
      (($code :initarg :code :reader os-error-code))
      (:report (lambda (c s)
                 (let ((code (os-error-code c)))
                   (format s "~S=~S: ~S" code (errno code) (strerror code))))))
where STRERROR returns the message for the code and ERRNO converts
between the symbolic and numeric codes.
Thus I will remove simple-os-error.  Objections?

However, while on unix there is only one kind of error (OS-error, errno),
windows have two kinds: OS-error (GetLastError) and ANSIC-error (errno).
Thus I have 4 options for windows:
- make os-error abstract and os-error-ansi & os-error-win32 inherit from it
- make os-error mean ansi C errno (like on unix) and os-error-win32
  inherit from it
- make os-error mean win32 GetLastError error and os-error-ansic inherit
  from it
- make a single os-error class with an extra slot $ANSICP which will
  tell me whether the code is errno or GetLastError; alternatively,
  store GetLastError as a negative number.

Any preferences?

-- 
Sam Steingold (http://sds.podval.org/) on CentOS release 5.6 (Final) X 11.0.60900031
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