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Problem Report 0761 Details

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Report 0761 Actions

    Problem Report Number 0761
    Submitter's Classification Specification problem
    State Resolved
    Resolution Temporary Interpretation (TIN)
    Problem Resolution ID TIN.X.0052
    Raised 1970-01-01 08:00
    Updated 2003-03-13 08:00
    Published 1995-09-09 08:00
    Product Standard Commands and Utilities V2 (UNIX 95)
    Certification Program The Open Brand certification program
    Test Suite VSC version 4.1.4
    Test Identification POSIX.upe/patch/patch 13
    Specification Commands and Utilities Issue 4 Version 2
    Location in Spec See Problem Text
    Problem Summary TIN4C.00009 Test of -D option should allow #ifndef use.
    Problem Text
    Historically, patch's -D option has used both #ifdef and #ifndef
    constructs. The IEEE interpretation PASC 1003.2-92 #69 states
    that POSIX.2's failure to allow the use of both constructs is
    a defect in the standard.

    Our implementation conforms to the draft POSIX.2b standard which
    more accurately describes historical behaviour in this area.
    Since this area of the specification is subject to change, we
    request a temporary interpretation allowing historical practice.
    Test Output
    200|46 1 17:53:03|TP Start
    520|46 1 462094346 1 1|Assertion #13 (C):
    520|46 1 462094346 1 1|Note: The behavior associated with this assertion is expected
    520|46 1 462094346 1 2|to change in a future revision of POSIX.2.
    520|46 1 462094346 1 3|-TC13- Output differs from the expected output
    220|46 1 1 17:53:12|FAIL

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    pasc-1003.2-69 requests

    POSIX.2 Subclause 5.22 specifies the semantics of the "patch" utility.
    In subclause 5.22.3 the behavior of the -D option is specified as
    follows:

    -D <define> Mark changes with the C preprocessor construct:

    #ifdef <define>
    ...
    #endif

    The option-argument <define> shall be used as the
    differentiating symbol.

    Can a conforming implementation of the patch utility use "#ifndef" to
    mark changes that constitute deletions from the original file? Can an
    implementation freely choose to use #ifdef or #ifndef when either is
    correct (i.e. gives a file that, after preprocessing, has the correct
    contents)? For example, the files

    aa
    #ifdef uppercase
    BB
    #else
    bb
    #endif
    cc

    and

    aa
    #ifndef uppercase
    bb
    #else
    BB
    #endif
    cc

    are equivalent in this sense. Are both valid output files from a call
    to a conforming "patch -D uppercase ..."?

    Note that the use of #ifndef is historical practice. Note also that if
    it is not permitted, implementations can still conform, but only
    through the use of such clumsy constructs as

    #ifdef <define>
    #else
    ...
    #endif

    In a similar vein: can a conforming implementation of "patch" use
    the construct

    #if defined(<define>)

    rather than

    #ifdef <define>

    In general, how broadly can the phrase "the C preprocessor
    construct:..." be interpreted?

    And delivers the following ruling

    The standard states the behaviour for #ifdef and #endif and conforming
    implementations must conform to this. The standard makes no restrictions
    for the use of further C preprocessor directives between #ifdef and #endif.
    The standard does not allow using #ifndef and #if defined in the manner
    specified in the interpretation request. Concerns about this are being
    refered to the sponsor.

    This would appear to disallow the requested use of #ifndef. However,
    POSIX 1003.2b/D11 states

    -D define Mark changes with one of the following C preprocessor
    constructs:

    #ifdef define
    ...
    #endif

    #ifndef define
    ...
    #endif

    optionally combined with the C preprocessor constrct #else

    Anticipating acceptance of POSIX 2003.2b and the eventual
    alignment of the tests with it a temporary interpretation is
    recommended.

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

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