closedir(3) handling NULL
brde at optusnet.com.au
Fri Jan 24 20:28:24 UTC 2014
On Fri, 24 Jan 2014, Garrett Wollman wrote:
> <<On Sat, 25 Jan 2014 06:00:08 +1100 (EST), Bruce Evans <brde at optusnet.com.au> said:
>> I don't know how the fd can be invalid for a (necessarily valid) stream.
>> Maybe because the fd for a stdio stream is not private, and POSIX actually
>> allows closing it directly. At least this says "shall fail" instead of
>> "may fail". I think the "may fail" for closedir() is just buggy wording.
>> The "may" is for the implementation not being required to use fd's at all.
>> But when it uses them, errors from them should be "shall fail" like they
>> are for fclose().
> "may fail" has a very specific meaning in the "ERRORS" section: if the
> implementation detects the condition described, it must use the
> specified error number.
That doesn't quite do it. Detection of the error for closing a closed fd
is still not required, unlike for fclose().
I could only find the above implied indirectly, and not completely.
% 435 RETURN VALUE
% 436 This section indicates the possible return values, if any.
% 437 If the implementation can detect errors, ``successful completion'' means that no error
% 438 has been detected during execution of the function. If the implementation does detect
% 439 an error, the error is indicated.
So if an error is detected, that error is "indicated". I think the indication
must be in the usual way, by storing in errno (except for these unsual APIs
where it is returned). This is already inconsistent with returning a
specific error. I think nothing prevents detection of a different error
(one not even listed in the ERRORS section) and nothing prevents returning
that error, while the above requires it.
% 440 For functions where no errors are defined, ``successful completion'' means that if the
% 441 implementation checks for errors, no error has been detected. If the implementation can
% 442 detect errors, and an error is detected, the indicated return value is returned and errno
% 443 may be set.
The only thing that is clear is that if an error is detected, the function
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