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Wed Jul 26 10:17:04 CEST 2006 · https://mail.python.org/pipermail/python-dev/2006-July/067706.html

Martin v. Löwis wrote:
> Neal Norwitz wrote:
>> # 61 Modules/_sqlite/cursor.c:599  Null pointer may be dereferenced
>>
>>     Null pointer 'self->statement' that comes from line 674 may be
>>     dereferenced by passing argument 1 to function
>>     'statement_mark_dirty' at line 599.
> 
> Looks like a problem. Maybe a break is missing after line 674?

The code is a bit complicated here, and admittedly not the nicest one, 
but I verified it and there is no problem here.

_query_execute() is designed to handle both executemany() and execute().

multiple is a local variable that is 1 if there is a set of tuples of 
SQL parameters (executemany) instead of a single tuple of SQL parameters 
(execute), in which case it's 0.

Before the while loop, the code makes sure that parameters_iter is an 
iterator that returns SQL parameter tuples. So if there is only a single 
parameter tuple, a temporary list is created an parameters_iter is an 
iterator over it.

So, if !multiple (referenced code in line 674), the while-loop will only 
be executed once, and in the second loop, the while-loop will exit 
because then the following code will break:

         parameters = PyIter_Next(parameters_iter);
         if (!parameters) {
             break;
         }

Code in line 599 is thus not executed with self->statement = 0.

-- Gerhard

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