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ID Category Severity Type Date Submitted Last Update
0001210 [1003.1(2016)/Issue7+TC2] System Interfaces Objection Error 2018-09-21 14:38 2018-11-12 15:07
Reporter geoffclare View Status public  
Assigned To
Priority normal Resolution Accepted  
Status Interpretation Required  
Name Geoff Clare
Organization The Open Group
User Reference
Section nftw()
Page Number 1397
Line Number 46455
Interp Status Approved
Final Accepted Text
Summary 0001210: FTW_MOUNT and symbolic links to directories on other file systems
Description Between the descriptions of FTW_MOUNT on the <ftw.h> page and the
nftw() page, it is clear that when a mount point is encountered it
is not reported (nftw() description) and is not crossed (<ftw.h>
description).

However, the same is not true for symbolic links to directories on
other file systems, when FTW_MOUNT is set and FTW_PHYS is clear.
Since the <ftw.h> description only refers to mount points, the
standard requires that nftw() does not report such directories
but does descend below them (if they are not also mount points), and
that it reports symbolic links found there that point back to the
original file system.

Of course, this is not how nftw() implementations behave. They do not
cross any directory with a different device ID, regardless of how it
was reached.
Desired Action On page 255 line 8562 section <ftw.h>, change:
FTW_MOUNT
The walk does not cross a mount point.
to:
FTW_MOUNT
The walk only reports files that have the same device ID as the starting directory and does not descend below directories that have a different device ID than the starting directory.

On page 1397 line 46455 section nftw(), change:
If set, nftw() shall only report files in the same file system as path.
to:
If set, nftw() shall only report files that have the same device ID (st_dev) as path and shall not descend below directories that have a different device ID than path.

On page 1400 line 46570 section nftw(), change RATIONALE from:
None.
to:
Earlier versions of this standard did not make clear that, as well as not reporting them, FTW_MOUNT prevents descent below directories that have a different device ID than path if they are encountered by following a symbolic link (rather than by being a mount point). This meant that if such a directory contained any symbolic links to files with the same device ID as path, nftw() with FTW_PHYS clear was required to report them. However, this was not how nftw() implementations behaved and the standard has been amended to match existing practice.
Tags tc3-2008
Attached Files

- Relationships
related to 0001133Resolved find clarification on -xdev behavior for mounted filesystem within primary 

-  Notes
(0004128)
shware_systems (reporter)
2018-09-27 15:28

The above does not take into account st_rdev, which is possibly necessary to disambiguate devices. A system, for example, might use st_dev to enumerate instances of SATA drives, and st_rdev to enumerate partitions on that drive.
(0004129)
Don Cragun (manager)
2018-09-27 15:49

The standard states the way in which the FTW_MOUNT flag is to be processed, and conforming implementations must conform to this. However, concerns have been raised about this which are being referred to the sponsor.

Rationale:
-------------
The description of this flag in the standard does not match the way historical implementations behaved. This changes the description in the standard to match historic behavior.

Notes to the Editor (not part of this interpretation):
-------------------------------------------------------
Make the changes suggested in the Desired Action.
(0004131)
kre (reporter)
2018-09-28 03:01

Someone please delete note 4128 ... st_rdev is provides the major/minor
for block and character device nodes, and has nothing whatever to do with
this issue, and any system which used it in the way suggested by the note
would be wildly broken. (When that note is deleted, this one can be as well.)
(0004138)
ajosey (manager)
2018-09-30 18:25

Interpretation proposed: 30 Sep 2018
(0004160)
ajosey (manager)
2018-11-12 15:07

Interpretation approved: 12 November 2018

- Issue History
Date Modified Username Field Change
2018-09-21 14:38 geoffclare New Issue
2018-09-21 14:38 geoffclare Name => Geoff Clare
2018-09-21 14:38 geoffclare Organization => The Open Group
2018-09-21 14:38 geoffclare Section => nftw()
2018-09-21 14:38 geoffclare Page Number => 1397
2018-09-21 14:38 geoffclare Line Number => 46455
2018-09-21 14:38 geoffclare Interp Status => ---
2018-09-21 14:52 geoffclare Relationship added related to 0001133
2018-09-27 15:28 shware_systems Note Added: 0004128
2018-09-27 15:49 Don Cragun Note Added: 0004129
2018-09-27 15:50 Don Cragun Tag Attached: tc3-2008
2018-09-27 15:50 Don Cragun Interp Status --- => Pending
2018-09-27 15:50 Don Cragun Status New => Interpretation Required
2018-09-27 15:50 Don Cragun Resolution Open => Accepted
2018-09-28 03:01 kre Note Added: 0004131
2018-09-30 18:25 ajosey Interp Status Pending => Proposed
2018-09-30 18:25 ajosey Note Added: 0004138
2018-11-12 15:07 ajosey Interp Status Proposed => Approved
2018-11-12 15:07 ajosey Note Added: 0004160


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