0000676: description of pread()/pwrite() on tty or socket inconsistent - Austin Group Defect Tracker

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ID

Category

Severity

Type

Date Submitted

Last Update

0000676

[1003.1(2013)/Issue7+TC1] System Interfaces

Editorial

Clarification Requested

2013-04-08 04:57

2019-06-10 08:55

Reporter

philip-guenther

View Status

public

Assigned To

ajosey

Priority

normal

Resolution

Accepted As Marked

Status

Closed

Name

Philip Guenther

Organization

OpenBSD

User Reference

Section

pread(), pwrite()

Page Number

1754,2288

Line Number

56422,72479

Interp Status

---

Final Accepted Text

See Note: 0001543.

Summary

0000676: description of pread()/pwrite() on tty or socket inconsistent

Description

The description of pread() says:
   An attempt to perform a pread() on a file that is incapable of
   seeking shall result in an error.

The ERRORS sections then says this:
  [ESPIPE] fildes is associated with a pipe or FIFO.

...but no error is given for using pread() on a socket or tty.

Testing indicates that Solaris 10 and FreeBSD 8.2 treat using pread() on a tty the same as doing a read() on it. For sockets, Solaris 10 treats pread() like read(), while FreeBSD fails with ESPIPE.

Linux 2.6.18 (RHEL 5.8) and OpenBSD 5.3 fail with ESPIPE for both ttys and sockets.

While the pwrite() DESCRIPTION doesn't make a statement about failing on unseekable file type, it does fail to describe ESPIPE as applying in the socket and tty cases. The four platforms tested (Solaris, FreeBSD, Linux, and OpenBSD) have the same behavior with pwrite() as they do with pread().

Desired Action

My inclination is that given the description and the underlying reason for using pread(), it should be required to fail with ESPIPE for these, but I can understand a decision to make it a "may fail" instead. If the former, then change:
  [ESPIPE] fildes is associated with a pipe or FIFO.
to
  [ESPIPE] fildes is associated with a pipe, FIFO, socket, or tty.

Otherwise, if the "may fail" route is chosen, then change this:
   An attempt to perform a pread() on a file that is incapable of
   seeking shall result in an error.
to (something like) this:
   An attempt to perform a pread() on a pipe or FIFO shall result in
   an error; an attempt to perform a pread() on other types of files
   that are incapable of seeking may result in an error.

and add to ERRORS:

The pread() function may fail, and the file pointer shall remain unchanged, if:
  [ESPIPE] fildes is associated with a socket or tty.

And then, either way, the same changes should be made to the write()/pwrite() page.

Tags

Relationships

Notes
(0001536) geoffclare (manager) 2013-04-08 08:48	It appears that this largely duplicates bugs 0000215 and 0000218, which were applied in TC1.

(0001537) philip-guenther (reporter) 2013-04-08 16:23	Yeah, the socket aspects were covered by those bugs; my apologies for the duplication. The tty aspects do still appear to apply, at least in my check of the preview of the 2013 HTML version (yay!) that was just posted. Another tweak to make if the pread/pwrite of tty case is made a "shall fail" error: the [EIO] errors that are specific to a background process accessing its controlling terminal should be moved into the part of the ERRORS section which is specific to the read() or write() function.

(0001543) Don Cragun (manager) 2013-04-21 00:23 edited on: 2013-04-21 00:27	Change the ESPIPE error condition description for pread() on P1754, L56422 from: The file is a pipe, FIFO, or socket. to: The file is incapable of seeking. Make the same change to the ESPIPE error condition description for pwrite() on P2288, L72479.

Issue History
Date Modified	Username	Field	Change
2013-04-08 04:57	philip-guenther	New Issue
2013-04-08 04:57	philip-guenther	Status	New => Under Review
2013-04-08 04:57	philip-guenther	Assigned To	=> ajosey
2013-04-08 04:57	philip-guenther	Name	=> Philip Guenther
2013-04-08 04:57	philip-guenther	Organization	=> OpenBSD
2013-04-08 04:57	philip-guenther	Section	=> pread
2013-04-08 04:57	philip-guenther	Page Number	=> 1739
2013-04-08 04:57	philip-guenther	Line Number	=> 55479-55480,55525
2013-04-08 08:48	geoffclare	Note Added: 0001536
2013-04-08 16:23	philip-guenther	Note Added: 0001537
2013-04-18 16:00	Don Cragun	Project	1003.1(2008)/Issue 7 => 1003.1(2013)/Issue7+TC1
2013-04-21 00:23	Don Cragun	Page Number	1739 => 1754,2288
2013-04-21 00:23	Don Cragun	Line Number	55479-55480,55525 => 56422,72479
2013-04-21 00:23	Don Cragun	Interp Status	=> ---
2013-04-21 00:23	Don Cragun	Note Added: 0001543
2013-04-21 00:27	Don Cragun	Note Edited: 0001543
2013-04-21 00:27	Don Cragun	Section	pread => pread(), pwrite()
2013-04-25 15:51	Don Cragun	Final Accepted Text	=> See Note: 0001543.
2013-04-25 15:51	Don Cragun	Status	Under Review => Resolved
2013-04-25 15:51	Don Cragun	Resolution	Open => Accepted As Marked
2013-04-25 15:52	Don Cragun	Tag Attached: tc2-2008
2019-06-10 08:55	agadmin	Status	Resolved => Closed

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