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Problem Report 0777 Details

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Report 0777 Actions

    Problem Report Number 0777
    Submitter's Classification Test Suite problem
    State Resolved
    Resolution Test Suite Deficiency (TSD)
    Problem Resolution ID TSD.X.0292
    Raised 1970-01-01 08:00
    Updated 2003-03-13 08:00
    Published 1998-09-18 08:00
    Product Standard Commands and Utilities V2 (UNIX 95)
    Certification Program The Open Brand certification program
    Test Suite VSC version 4.1.6
    Test Identification POSIX.annexA/lex 93
    Problem Summary TSD4C.00219 This test may core dump on implementations because input() calls yywrap() and may recurse.
    Problem Text
    This request is based on SR #2502.

    This test is failing because it depends on a particular implementation's
    input() function in a way that the standards are silent on.
    Specifically, it is calling the input() function from the test's
    yywrap() function. In the original lex implementation from AT&T this
    worked because input() was just a macro that read up to the end-of-file
    but no further. In another implementation, specifically flex version
    2.5.4, the input() function calls yywrap() when it reaches end-of-file.
    The leads to en infinite recursion with test #93 which eventually fails
    when the stack can't be grown any more. The standards have the following
    to say about yywrap() and input():

    The functions or macros defined below are accessible to user code
    included in the lex input. It is unspecified whether they appear in
    the C code output of lex or are accessible only through the -l l
    operand to c89 (the lex library).
    ...
    int input(void)
    Returns the next character from the input, or zero on end of
    file. It shall obtain input from the stream pointer yyin,
    although possibly via an intermediate buffer. Thus, once
    scanning has begun, the effect of altering the value of yyin is
    undefined. The character read is removed from the input stream
    of the scanner without any processing by the scanner.
    ...
    The following functions appear only in the lex library accessible
    through the -l l operand; they can therefore be redefined by a
    portable application:
    ...
    int yywrap(void)
    Called by yylex() at the end of file; the default yywrap()
    always shall return 1. If the application requires yylex() to
    continue processing with another source of input, then the
    application can include a function yywrap(), which associates
    another file with the external variable FILE *yyin and will
    return a value of zero.
    ...

    The specifications above seem to imply that input() will only read from
    the current yyin stream and that yywrap() will only be called by
    yylex(). However, neither of these two points are explicitly specified.
    Thus, test #93 is explicitly depending on undefined behavior from the
    standard.
    Test Output
    520|0 1 809689 1 1|Assertion #93 (C): Test input() behavior
    520|0 1 809689 1 11|Expected exit code = 0; Received 139
    520|0 1 809689 1 12|Standard output isn't the same as file 'lex_eso_93_1'
    520|0 1 809689 1 13|diff of "out.stdout" and "lex_eso_93_1":
    520|0 1 809689 1 14|*** out.stdout Thu Apr 9 09:20:08 1998
    520|0 1 809689 1 15|--- lex_eso_93_1 Thu Apr 9 09:20:06 1998
    520|0 1 809689 1 16|***************
    520|0 1 809689 1 17|*** 0 ****
    520|0 1 809689 1 18|--- 1,6 ----
    520|0 1 809689 1 19|+ rr
    520|0 1 809689 1 20|+ rpassed first input() test
    520|0 1 809689 1 21|+ ating
    520|0 1 809689 1 22|+ rr
    520|0 1 809689 1 23|+
    520|0 1 809689 1 24|+ passed second input() test
    220|0 1 1 09:24:08|FAIL

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    We agree this is a test suite deficiency in the test
    suite version(s) listed.

    Note that flex does not exhibit compliant behavior with this issue
    resolved. The test subsequently fails because input() returns -1
    instead of 0 due to differences in the processing of null characters.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Test Suite Deficiency (TSD)
    Review Conclusion
    This is an agreed Test Suite Deficiency.

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