New submission from Louie Lu:
This is a sub-problem of #9285, in #9285, we aim to provide cProfile and
profile a context manager, this will need to add code like this:
def __enter__(self):
self.set_cmd('')
sys.setprofile(self.dispatcher)
return self
Unfortunately, when setting up profiler via `sys.setprofile`, it will
immediately work on next line `return self`, which cause the assertion inside
`trace_dispatch_return` claim this is a "Bad return".
Technically, `profile.Profile` can not go return upper than it's frame inside
the frame stack. This behavior can be observed by this code:
def fib(n):
if n > 2:
return fib(n - 1) + fib(n - 2)
return n
def foo():
pr = profile.Profile()
# Profile was set in the `foo` frame, it can't get more upper than this
# that means, we can't return to global frame when this profile is set
sys.setprofile(pr.dispatcher)
fib(5)
# We didn't stop the profile here via sys.setprofile(None)
# So it will return 0xDEADBEAF to global frame and cause a bad return
return 0xDEADBEAF
foo()
Here this issue will provide the test of this behavior, then will make some
modify in #9285 to prevent this situation when using profile as a context
manager.
----------
components: Library (Lib)
messages: 291957
nosy: louielu, ncoghlan
priority: normal
severity: normal
status: open
title: Add profile test case for trace_dispatch_return assertion
type: enhancement
versions: Python 3.7
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Python tracker <[email protected]>
<http://bugs.python.org/issue30113>
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