standards/171572: ptsname(-1) returns errno 0

[Sergey Kandaurov]

The following reply was made to PR standards/171572; it has been noted by GNATS.

From: Sergey Kandaurov <pluknet at gmail.com>
To: Ed Maste <emaste at freebsd.org>
Cc: bug-followup at freebsd.org
Subject: Re: standards/171572: ptsname(-1) returns errno 0
Date: Wed, 12 Sep 2012 18:07:16 +0400

 On 12 September 2012 17:53, Ed Maste <emaste at freebsd.org> wrote:
 > On 12 September 2012 09:40, Sergey Kandaurov <pluknet at gmail.com> wrote:
 >> This is regression (or was it an intended change?) from 8.x's MPSAFE TTY:
 >>
 >> in 8.x ptsname() was changed so that:
 >> /* Make sure ptsname() does not overwrite errno. */
 >
 > It looks like it was intentional, probably based on:
 >
 > http://pubs.opengroup.org/onlinepubs/007904975/functions/ptsname.html:
 >
 > ERRORS
 >
 >     No errors are defined
 >
 > I guess this was interpreted as "shall not set errno."
 >
 > However - http://austingroupbugs.net/view.php?id=503:
 >
 > At line 54750, after "shall return a null pointer", add ", and may set errno".
 >
 > At line 54754, replace "No errors are defined." with:
 >
 > The ptsname( ) function may fail if:
 > [EBADF] The fildes argument is not a valid file descriptor.
 > [ENOTTY] The file associated with the fildes argument is not a master
 > pseudo-terminal device..
 >
 > There's some further discussion on ENOTTY vs EINVAL there.  It looks
 > like we should at least set errno though:
 
 Oh, well in 7.x before MPSAFE TTY ptsname() used to return:
      [EINVAL]           fildes is not a master pseudo-terminal device.
 and the errors specified for the fstat(2) system call.
 
 Probably the only we should change is to turn EINVAL into ENOTTY for !master pt
 (change __isptmaster()) and  return errors from fstat() as is if any.
 
 -- 
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 pluknet