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Problem Report 0355 Details

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Report 0355 Actions

    Problem Report Number 0355
    Submitter's Classification Specification problem
    State Resolved
    Resolution Temporary Interpretation (TIN)
    Problem Resolution ID TIN.X.0007
    Raised 1993-10-22 08:00
    Updated 2003-03-13 08:00
    Published 1993-10-27 08:00
    Product Standard Internationalised System Calls and Libraries (XPG4)
    Certification Program The Open Brand certification program
    Test Suite VSX4 version 4.2.4
    Test Identification POSIX.os/devclass/c_iflag 19, 20
    Specification System Interfaces and Headers Issue 4
    Location in Spec See Problem Text
    Problem Summary TIN4.007 This test case enables START/STOP input control by setting the XOFF flag in the terminal device. It also enables START/STOP output control by setting the XON flag in the loopback device. The test case...
    Problem Text

    This test case enables START/STOP input control by setting the XOFF
    flag in the terminal device. It also enables START/STOP output control
    by setting the XON flag in the loopback device. The test case then fills
    up the input queue of the terminal device by writing to the loopback device.
    Following this, it reads from the loopback device, expecting
    a STOP character to be in the input (the terminal device should
    have sent a STOP character when its input queue was filled).
    Next, the test case reads all of the data from the terminal device,
    emptying its input queue. Following this, it reads from the loopback
    device, expecting a START character to be in the input (the terminal device
    should have sent a START character when its input queue was emptied).

    These tests fail on SVR4-based systems due to the way XON/XOFF
    is implemented. The implementation of XON/XOFF is done with ioctls
    (M_START, M_STOP, M_STOPI, and M_STARTI) in a manner similar to the
    implementation of tcflow() in SVR4. No START/STOP character is
    actually written to the data stream. Therefore, no STOP/START
    character will be present in the data read from the loopback connection.

    c_iflag 20

    This test case sometimes fails because all data written in the previous
    test case (c_iflag 19) is not always flushed when flushem() is performed
    in the setup. The test case expects all data remaining from previous test
    cases in the input and output queues of both the terminal device and
    the loopback device to be flushed in flushem() when tcflush(..., TCIOFLUSH)
    is executed.

    This test case will sometimes work and sometimes fail because it
    is timing dependent due to the way SVR4-based pseudo ttys are
    set up in XPG4. When the data is flushed from the loopback connection,
    it is possible that the process reading data from the tty connection
    has read some data from the stream head and has not yet written it to the
    loopback connection before the flush of the data on the loopback connection
    is executed. Similarly, when the data is flushed from the tty connection,
    it is possible that the process reading data from the loopback connection
    has read some data from the stream head and has not yet written it to the
    tty connection before the flush of the data on the tty connection is
    executed. The result of all data not being flushed is that it can be read
    by subsequent reads, causing the test case to fail.

    Test Output

    ************************************************************************
    /tset/POSIX.os/devclass/c_iflag/T.c_iflag 19 Failed

    Test Description:
    If general terminal interface supported:
    When IXOFF is set the system shall transmit one or more STOP
    characters as needed to prevent the number of characters in the
    input queue from exceeding its capacity. The system shall transmit
    one or more START characters as needed to start transmitting data.
    CONDITIONAL: If _POSIX_MAX_INPUT <= MAX_INPUT <= PCTS_MAX_INPUT
    assertion is base (type C) otherwise assertion is extended (type
    D).
    Posix Ref: Component Settable Parameters Assertion 7.1.2.2-32(C:D)
    Posix Ref: Component Settable Parameters Assertion 7.1.2.2-33(C:D)

    Test Strategy:
    OPEN and initialise terminal file and loop back file (having SAME
    parity)
    OBTAIN max_input from fpathconf(tty_fildes, _PC_MAX_INPUT)
    SET IXON, VMIN=0 and VTIME=10 in loop back control flags
    CLEAR ICANON in loop back control flags
    SET IXOFF, VMIN=0 and VTIME=10 in terminal control flags
    CLEAR ICANON in terminal control flags
    CREATE child process
    UNTIL a timeout occurs
    SET TIMEOUT of WAITTIME/2 seconds
    WRITE string to loop back file
    FLUSH output queue on loop back file using tcflush(fd, TCOFLUSH)
    READ entire input queue from terminal file
    SET capacity to the greater of the number of bytes read and
    max_input
    CLEAR IXON in loop back control flags
    UNTIL capacity bytes have been written
    WRITE string to loop back file
    SLEEP to allow data to transfer to terminal file
    READ from loop back file
    VERIFY that read() read at least one STOP character
    UNTIL capacity bytes have been read or a read error occurs
    READ from terminal file
    SLEEP to allow more data to become available
    VERIFY that capacity bytes in total were read
    READ from loop back file
    VERIFY that read() read at least one START character

    Test Information:
    after input queue filled to 1598 bytes, attempt
    to read() STOP character(s) returned 0, expected >= 1
    ************************************************************************

    ************************************************************************
    /tset/POSIX.os/devclass/c_iflag/T.c_iflag 20 Failed

    Test Description:
    If general terminal interface supported:
    When IGNCR and ICRNL are both clear, a received CR character is not
    altered during input processing.
    Posix Ref: Component Settable Parameters Assertion 7.1.2.2-27(C)

    Test Strategy:
    OPEN and initialise terminal file and loop back file (having SAME
    parity)
    SET VMIN to 1 and VTIME to 0
    CLEAR ICRNL, IGNCR and ICANON in terminal control flags
    WRITE one character CR to loop back file
    VERIFY that read() from terminal file returned 1
    VERIFY that read() read character CR

    Test Information:
    read() returned 48, expected 1
    ************************************************************************

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    This is the subject of a current POSIX interpretation and it is recommended
    that a temporary interpretation is granted pending the outcome of the
    discussions at the POSIX level.

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

    Problem Reporting System Options:

     

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