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Problem Report 0429 Details

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Report 0429 Actions

    Problem Report Number 0429
    Submitter's Classification Specification problem
    State Resolved
    Resolution Rejected (REJ)
    Problem Resolution ID REJ.X.0048
    Raised 1993-11-24 08:00
    Updated 2003-03-13 08:00
    Published null
    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
    Problem Summary PG4R.048 c_iflag 19 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. Th...
    Problem Text
    c_iflag 19

    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 fails due to the failure in the previous test case
    (c_iflag 19). It executes flushes (using tcflush(...., TCIOFLUSH)) on
    both loop and tty side of its loopback construct, and expects
    all data to now be removed. This is not the case, however, due
    to the way the loopback is constructed. This test case passes if
    test case 19 is not executed.

    The masters from both the loop side and the tty side are connected
    through the use of two user processes. One process reads from the
    loop side and writes to the tty side, and the other process does the
    opposite. This is where the trouble lies: The previous test case
    finds the "capacity" of the loopback by writing until the write()
    blocks, then reading all the data. Then it floods the loopback
    with this same amount of data, and fails for the reasons mentioned
    in the previous explanation. This leaves the loopback with all
    queues full, and also one of the user process that connects the two
    masters is blocked, waiting to write.

    Now, test case 20 tries to clear the construct, by flushing both the
    tty and loop side. However, this does not remove the data that
    is held by the connecting process which is blocked on write.
    The flushes clear all the queues. The process that had been blocked
    on the write now puts the 47 bytes left over from test case 19 into
    the read queue on the tty side. Thus, test 20 will always see the extra
    47 bytes of data (which is the string that was continually written in
    c_iflag 19), and will always 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
    A temporary interpretation has already been granted for these two tests
    pending a resolution of the interpretation via the IEEE interpretations
    process. This interpretation has not yet been completed.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Rejected (REJ)
    Review Conclusion
    This request is refused. Please refer to TIN4.007.

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