[Python-Dev] recursion limit in marshal

"Martin v. Löwis" martin at v.loewis.de
Fri May 18 07:52:40 CEST 2007

> The point of this message is to see if anyone thinks 2000 is
> unreasonable.  It could probably be raised, but I'm not going to try
> it since I don't have access to a Windows box.  Testing this remotely
> sucks.

If this turns out ever to be a limitation, I would challenge the
reporter to rewrite marshal in a non-recursive manner.

It shouldn't be that difficult: w_object should operate a queue of
objects yet to be written, and Tuple, Dict, Set (why does marshal
support writing sets, anyway?) would all just add things to the
queue rather than recursively invoking w_object.

The only challenge would be code objects, which have a w_long
interspersed with the w_object calls. I would fix this by changing
the marshal format of code objects, to move the co_firstlineno to the

For reading, a heap-managed stack would be necessary, consisting
of a (type, value, position, next) linked list. Again, code
objects would need special casing, to allow construction with
NULL pointers at first, followed by indexed setting of the code
fields. For lists and tuples, position would define the next
index to be filled; for dictionaries, it would not be needed,
and for code objects, it would index the various elements of
the code object.


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