New submission from Dan Snider <[email protected]>:
As far as I know, generators, set comprehensions, list comprehensions, and dict
comprehensions, (along with their asynchronous variants) are implemented by
first calling the GET_(A)ITER opcode and then building and calling a function
that acepts the resulting iterator as its sole argument.
Assigning the code object used to make that function (or using it in the
types.FunctionType constructor) and then calling it with a non-iterator
argument will obviously cause a crash since the FOR_ITER opcode rightly expects
that it will never have to deal with non-iterators and calls tp_iternext
without checking if it exists.
The 4-liner demonstrates the crash:
if 1:
fn = lambda: None
gi = (i for i in ())
fn.__code__ = gi.gi_code
[*fn("abc")]
----------
messages: 342797
nosy: bup
priority: normal
severity: normal
status: open
title: Calling "functions" used to implement generators/comps easily cause crash
type: crash
versions: Python 3.6, Python 3.7, Python 3.8
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Python tracker <[email protected]>
<https://bugs.python.org/issue36956>
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