Hi all,

In working on the LLVM/LLDB project, I've been hitting a bug in the
embedded interpreter that causes a NULL dereference in the Python
readline module. There is a call to the history_get() function with an
assumption that it returns a non-NULL value. This is not guaranteed to
be true of the history_get function, and causes the readline module to
crash when it hits this condition.

I'm attaching a patch to the Python 2.7.6 source code that addresses
this issue. It adds an explicit NULL test of the history_get() return
value before accessing it.

This issue was discovered in top of tree LLDB (LLVM.org debugger project).  See here for details:

http://llvm.org/bugs/show_bug.cgi?id=18841