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Problem Report 1625 Details

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Report 1625 Actions

    Problem Report Number 1625
    Submitter's Classification Specification problem
    State Resolved
    Resolution Permanent Interpretation (PIN)
    Problem Resolution ID PIN.X.0182
    Raised 1997-10-29 08:00
    Updated 2003-03-13 08:00
    Published 1997-11-05 08:00
    Product Standard Internationalised System Calls and Libraries Extended (UNIX 95)
    Certification Program The Open Brand certification program
    Test Suite VSU version 4.1.1
    Test Identification CAPI.os/genuts/nftw 3
    Specification System Interfaces and Libraries Issue 4 Version 2
    Location in Spec See Problem Text
    Problem Summary PIN4U.00048 This test may fail on implementations that exhibit behavior allowed by Base Resolution 97-003.
    Problem Text
    Based on a Base Working Group resolution request we initiated we
    ask for a waiver for this test. The details of the resolved resolution
    can be found at:-

    http://www.rdg.opengroup.org/mem_only/tech/base/resns/eastwood/bwg97-003.html

    For ease we list the resolution here:-



    97 #003


    ____________________________________________________________________________
    _

    Topic: nftw
    Relevant Sections: nftw
    Spec: XSH Issue 4 Version 2 & Issue 5

    Resolution Request:
    -------------------

    The test for nftw fails as follows:


    TEST PURPOSE #3
    A call to int nftw(const char *path, int (*fn)(const
    char *, const struct stat *, int, struct FTW *), int
    depth, int flags) when flags does not contain FTW_PHYS
    shall follow links instead of reporting them and shall
    not report the same file twice.
    PREP: Set up the path
    TEST: nftw without FTW_PHYS follows symbolic links
    INFO: Call to fn() at ../tmp/data/dirl
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_left.1
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_left.1/dir_left.2
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_left.1/dir_left.2/left.3
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_right.1
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_right.1/dir_right.2
    INFO: Call to fn() at
    ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_right.1/dir_right.2/right.3
    INFO: Call to fn() at ../tmp/data/dirl/dir_right.1
    INFO: Call to fn() at ../tmp/data/dirl/dir_right.1/dir_right.2
    INFO: Call to fn() at ../tmp/data/dirl/dir_right.1/dir_right.2/right.3
    ERROR: Target of right.3 was already reported so this file should not be
    3 FAIL

    On looking at this result we see that the test does test what the specification
    says and we feel that there is a specification error here. The previous test
    tests what is established historical practice and is what the SVID III defines
    as the functionality in this area. It appears that when the SVID was included
    to create the XPG4.2 specifications a rewrite of some of the words has changed
    the meaning in a detrimental way.

    The FTW_PHYS wording from the SVID, on which the nftw() entry is
    based says "Physical walk, does not follow symbolic links. Otherwise,
    nftw() will follow links but will not walk down any path that crosses
    itself." Somehow, the XSH4.2 wording became "... If clear, nftw()
    will follow links instead of reporting them, and will not report the
    same file twice."

    The existing practice is to keep information about *directories*.
    If one is about to start walking through the directory entries for
    a directory with the same device/inode pair for one we've got "on
    the stack", we instead immediately close the directory and skip it.
    That's all. This requires, for a recursive nftw() implementation,
    exactly one item on the stack/directory-call.

    To perform to the letter of the XSH4.2 words, the implementation
    must record the device/inode pair for *every file* reported during
    the entire call and for each new entry, check to see if it has the
    same pair! This forces an additional O(n) in space and at least
    O(n log n) time for "n" files reported. It doesn't even help if
    the description is taken to mean that only files reached for a
    second or subsequent time through only *symbolic* links are to be
    checked for, since we still need to keep the device/inode pairs
    for all the regular files in case a symbolic link comes later.

    We believe this is an incorrect technical editorial modification to the
    nftw() functionality which in XPG4.2 was to standardise on existing
    practice as identified by the SVID.


    This is referred to the Base WG to query if the change from
    historical behaviour was the intent.

    Resolution Response
    -------------------

    A future revision will replace the FTW_PHYS clause of nftw()
    with the following text. For existing conforming either behaviour is
    allowed.

    FTW_PHYS If set, nftw() performs a physical walk and does not follow
    symbolic links.

    If FTW_PHYS is clear and FTW_DEPTH is set,
    nftw() will follow links instead of reporting them,
    but will not report any directory that would be a descendant
    of itself. If FTW_PHYS is clear and FTW_DEPTH is clear, nftw() will follow
    links instead of reporting them, but will not report the contents
    of any directory that would be a descendant of itself.


    Rationale
    -------------
    This matches historical behaviour.



    Test Output
    TEST PURPOSE #3
    A call to int nftw(const char *path, int (*fn)(const
    char *, const struct stat *, int, struct FTW *), int
    depth, int flags) when flags does not contain FTW_PHYS
    shall follow links instead of reporting them and shall
    not report the same file twice.
    PREP: Set up the path
    TEST: nftw without FTW_PHYS follows symbolic links
    INFO: Call to fn() at ../tmp/data/dirl
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_left.1
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_left.1/dir_left.2
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_left.1/dir_left.2/left.3
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_right.1
    INFO: Call to fn() at ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_right.1/dir_right.2
    INFO: Call to fn() at
    ../tmp/data/dirl/dir_left.1/dir_left.2/left.3/dir_right.1/dir_right.2/right.3
    INFO: Call to fn() at ../tmp/data/dirl/dir_right.1
    INFO: Call to fn() at ../tmp/data/dirl/dir_right.1/dir_right.2
    INFO: Call to fn() at ../tmp/data/dirl/dir_right.1/dir_right.2/right.3
    ERROR: Target of right.3 was already reported so this file should not be
    3 FAIL

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    A permanent interpretation is recommended.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Permanent Interpretation (PIN)
    Review Conclusion
    A Permanent Interpretation is granted.

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