[issue14507] Segfault with deeply nested starmap calls

[Raymond Hettinger]

Raymond Hettinger <raymond.hettinger at gmail.com> added the comment:

[Kristján]
> a = map(add, a, b) also crashes this.
> ...  What's happening here is just simple c recursion 
> trough function pointers, ending in stack overflow, ...

Thanks for the analysis.  ISTM, this bug report is getting less and less interesting (or at least, less actionable without heavy-handed interventions in multiple tools).

One other thought, the OPs isn't really recursive in the sense of a function calling itself repeatedly.  Instead, the OPs explicitly creates a heavily nested pile of distinct iterator objects and then runs the entire chain.  This isn't much different from someone writing:  os.system('cat somefile | ' + ' | '.join(['sort']*100000)).

The existing sys.max_recursion_depth was put in as a defense against the relatively common mistake of users writing a recursive function and getting the termination code wrong.   I don't think that logic would apply to intentionally deeply nested data structures or iterators.

Stackoverflows in C are hard to protect against.  We could take every iterator and set some limits on it, but that would be heavy handed and likely do more harm than good (C iterators have been around almost a decade and haven't done fine in the wild.  The itertools in particular were designed to gain speed through by-passing the eval-loop.  Slowing them down would be counter to their primary use case.)

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resolution:  -> later

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue14507>
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