[Dev] Mac recursion limit?

[Phillip J. Eby]

Bug 2563 was causing core dumps on Mac OS X because of Python's recursion 
limit being set too high.  I don't have a Mac to test this on, but it's 
probably an indication that Chandler should lower Python's maximum 
recursion depth so that if such an error occurs, it will result in an 
exception rather than a core dump.  I found the following script that will 
test Python's recursion limit on a given platform:

http://cvs.sourceforge.net/viewcvs.py/python/python/dist/src/Misc/find_recursionlimit.py?rev=HEAD&view=auto

But it needs a couple of changes to work for what we're trying to do.  As 
written, it assumes that Python's default limit is safe, and only tests 
*higher* recursion limits.  It also only tests the main thread, and the 
issue in bug 2653 was that non-main threads have less stack space available.

So, maybe someone with a Mac could run this script with a couple of 
modifications: first, changing it to run the tests in a thread, and second, 
to start with a lower initial recursion limit (say 100) and smaller steps 
(maybe 10?) in order to find out where the crash point is.  The script is 
designed to output "Limit of 1000 is fine", "Limit of 1100 is fine", etc. 
until it crashes, so we would then have a measurement of what the limit 
should be set to on Mac OS X to prevent runaway recursion in a background 
thread from crashing Chandler.  This would be especially helpful in the 
case of third-party packages that might contain hidden runaway recursion, 
as bug 2653 was caused by ZaoBao's feedparser module.  With a safe memory 
limit, feedparser's behavior would not have caused any problems (which is 
why it worked on platforms where Python's default 1000 limit is safe).