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Problem Report 0356 Details

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Report 0356 Actions

    Problem Report Number 0356
    Submitter's Classification Specification problem
    State Resolved
    Resolution Temporary Interpretation (TIN)
    Problem Resolution ID TIN.X.0008
    Raised 1994-11-05 08:00
    Updated 2003-03-13 08:00
    Published 1994-06-08 08:00
    Product Standard Internationalised System Calls and Libraries (XPG4)
    Certification Program The Open Brand certification program
    Test Suite VSX4 version 4.3.2
    Test Identification POSIX.os/devclass/i_spchars 20,24
    Specification System Interfaces and Headers Issue 4
    Location in Spec See Problem Text
    Problem Summary TIN4.008 This is a gray area in POSIX. The referenced POSIX subsection says that setting the value of any of the special characters to _POSIX_VDISABLE turns off its special function. Nothing is said about the ...
    Problem Text
    This is a gray area in POSIX. The referenced POSIX subsection says
    that setting the value of any of the special characters to
    _POSIX_VDISABLE turns off its special function. Nothing is said about
    the function of a related character.

    The tests in question turn on IXON and/or IXOFF, then turn off either
    the START or STOP character by setting its value to _POSIX_VDISABLE.
    Then, they write the other character (the counterpart of START or
    STOP), followed by a newline through the loopback. They expect that
    the written character will be eaten.

    The serial port firmware where this test is failing feels that if
    you've turned off START, then STOP shouldn't have any special meaning.
    (How would you restart the output?) STOP isn't eaten. And, if STOP
    is turned off, then START isn't eaten.

    That's why these tests fail when run with some serial port hardware.
    Test Output
    ************************************************************************
    /tset/POSIX.os/devclass/i_spchars/T.i_spchars 20 Failed

    Test Description:
    If general terminal interface supported:
    When _POSIX_VDISABLE is in effect for the terminal file, and START
    and STOP characters can be changed, when the value of START or STOP
    is set to the value _POSIX_VDISABLE (obtained from fpathconf()),
    then the action associated with that special character does not
    occur for any character received.
    Posix Ref: Component Terminal Interface Assertion 7.1.1.9-66(C)
    Posix Ref: Component FPATHCONF Assertion 5.7.1.2-25(A)

    Test Strategy:
    OPEN and initialise terminal file and loop back file
    CLEAR NOFLSH and set ICANON and ISIG in terminal control flags
    SET value of STOP character to _POSIX_VDISABLE
    WRITE all non-special characters (last one NL) to loop back file
    READ from terminal file
    VERIFY that read() read all data written
    VERIFY that all other special characters' functions are enabled
    SET value of STOP character to original value
    SET value of START character to _POSIX_VDISABLE
    WRITE all non-special characters (last one NL) to loop back file
    READ from terminal file
    VERIFY that read() read all data written
    VERIFY that all other special characters' functions are enabled

    Test Information:
    with STOP set to _POSIX_VDISABLE, START character was read
    with START set to _POSIX_VDISABLE, STOP character was read
    ************************************************************************

    ************************************************************************
    /tset/POSIX.os/devclass/i_spchars/T.i_spchars 24 Failed

    Test Description:
    If general terminal interface supported:
    When _POSIX_VDISABLE is in effect for the terminal file, and START
    and STOP characters can be changed, when the value of START or STOP
    is set to the value _POSIX_VDISABLE (obtained from pathconf()),
    then the action associated with that special character does not
    occur for any character received.
    Posix Ref: Component Terminal Interface Assertion 7.1.1.9-66(C)
    Posix Ref: Component PATHCONF Assertion 5.7.1.2-47(A)

    Test Strategy:
    OPEN and initialise terminal file and loop back file
    CLEAR NOFLSH and set ICANON and ISIG in terminal control flags
    SET value of STOP character to _POSIX_VDISABLE
    WRITE all non-special characters (last one NL) to loop back file
    READ from terminal file
    VERIFY that read() read all data written
    VERIFY that all other special characters' functions are enabled
    SET value of STOP character to original value
    SET value of START character to _POSIX_VDISABLE
    WRITE all non-special characters (last one NL) to loop back file
    READ from terminal file
    VERIFY that read() read all data written
    VERIFY that all other special characters' functions are enabled

    Test Information:
    with STOP set to _POSIX_VDISABLE, START character was read
    with START set to _POSIX_VDISABLE, STOP character was read
    ************************************************************************

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    The X/Open and POSIX.1-1990 specifications both state that "If the value
    of one of the changeable special control characters is {_POSIX_VDISABLE},
    that function is disabled; that is, no input data will be recognised as the
    disabled special character." This could be considered to mean that "only
    that function is disabled" and that the other special control characters
    remain unchanged. The system under test has taken an alternative
    interpretation which suggests that, in the case of START or STOP, the
    other character (STOP or START respectively) can also be disabled. An
    alternative course of action for the system under test would be to treat
    an incoming non-disabled STOP or START as a special character which should
    be discarded in the case that the other character (START or STOP) is to be
    discarded.

    Many systems do not allow the START or STOP characters to be changed or
    discarded and any well written application should either discard both
    characters or treat them both as special.

    As an interpretation, this should be forwarded to the IEEE for a formal
    interpretation. Considering the likelihood of minimal impact on applications
    it is recommended that a temporary interpretation be granted until the
    response from the IEEE is known.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Temporary Interpretation (TIN)
    Review Conclusion
    This is granted as a temporary interpretation and will be
    forwarded to the IEEE.

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