It's possible to produce segfaults using two functions
from the
readline module by giving them negative values (GNU
readline 4.3-10),
at least in some circumstances.  

Python 2.5a0 (#10, Dec 15 2004, 19:53:33) 
[GCC 3.3.3 (Debian 20040401)] on linux2
Type "help", "copyright", "credits" or "license" for
more information.
>>> import readline
[25290 refs]
>>> readline.remove_history_item(-1)
Segmentation fault

>>> readline.replace_history_item(-1,'abc')
Segmentation fault

gdb reveals it happens because the (external)
remove_history and replace_history_entry don't return
NULL in these cases.  I'm not sure whether we're
responsible for checking the sanity of inputs or the
GNU code should be returning NULL and isn't, but at
least sometimes it doesn't.

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Hmm.  I can't reproduce this (also with readline 4.3).  Odd.

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FYI, I can reproduce this with :

- Python 2.4 & readline 4.3 under SuSE 9.1
- Python 2.5(snapshot as of 2004-12-17) & readline 4.3 under 
SuSE 9.1
- Python 2.4 & readline 4.3.5(?) under Cygwin

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Do you want to fix it then? :)  I can't imagine it's that hard, but it would 
be easier for someone who can test that their fix helps...

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I'm +1 for sanity checking rather than waiting for the GNU
readline to return NULL in these functions.

It's just adding a few lines of code right after 
PyArg_ParseTuple :

  if (entry_number < 0) {
    PyErr_SetString(PyExc_ValueError,
                    "index cannot be a negative value");
    return NULL;
  }

Then you can work around the problem without worrying 
about the return value of remove_history nor 
replace_history_entry.

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This one being simple enough for the likes of me to patch, I
did so -- 1093585.  Let the school of hard knocks begin!

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I can confirm the bug with readline 4.3 and Python 2.5a0
(#1, Jan 11 2005, 23:22:16). dsm001's patch fixes it.

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This should be now fixed with patch 1093585.