[Csv] Something's fishy...

[Skip Montanaro]

I rearranged the dialect initialization stuff a bit earlier today, then
started getting segfaults from the interpreter.  From gdb I was able to
track it down to what looked like an invalid keyword_args parameter passed
to csv_parser():

    (gdb) p args
    $1 = (PyObject *) 0x418030
    (gdb) pyo args
    object  : ()
    type    : tuple
    refcount: 1911
    address : 0x418030
    $2 = void
    (gdb) p keyword_args
    $3 = (PyObject *) 0xb3b0c0
    (gdb) pyo keyword_args
    object  : {'delimiter': ',', 'escapechar': None, 'lineterminator': 
    Program received signal EXC_BAD_INSTRUCTION, Illegal instruction/operand.
    0x0067d940 in ?? ()
    The program being debugged was signaled while in a function called from GDB.
    GDB remains in the frame where the signal was received.
    To change this behavior use "set unwindonsignal on"
    Evaluation of the expression containing the function (_PyObject_Dump) will be abandoned.

pyo is a user-defined gdb command:

    define pyo
    print _PyObject_Dump($arg0)
    end

Figuring there was maybe something wrong there, I stuck a print statement in
csv.py:_OCcsv:__init__ just before the last line of the method:

    print ">>", parser_options

The segfault went away.  I was left with a lot of output and one error:

    % python test_csv.py
    >> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    ..>> {'delimiter': '\t', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    ...E>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': None, 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 0, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': '\\', 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 3, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': '\\', 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 3, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': '\\', 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 2, 'doublequote': True}
    .>> {'delimiter': ',', 'escapechar': '\\', 'lineterminator': '\r\n', 'skipinitialspace': False, 'quotechar': '"', 'quoting': 2, 'doublequote': True}
    .
    ======================================================================
    ERROR: test_register (__main__.TestDialects)
    ----------------------------------------------------------------------
    Traceback (most recent call last):
      File "test_csv.py", line 200, in test_register
        csv.unregister_dialect("myexceltsv")
    AttributeError: 'module' object has no attribute 'unregister_dialect'

    ----------------------------------------------------------------------
    Ran 38 tests in 0.314s

    FAILED (errors=1)

I added the missing function.  Everything seems fine once again.  I'm
checking in what I have, but _csv.c should probably be carefully inspected
to see if there's an argument out of place, a missing INCREF, an array
bounds violation, or something similar.  Errors don't just magically go
away.  Whatever was wrong is still wrong, just hiding.

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