[Python-Dev] cProfile with generator throwing

Georg Brandl g.brandl at gmx.net
Sat Jun 9 09:42:08 CEST 2007

Eyal Lotem schrieb:
> Hi. It seems that cProfile does not support throwing exceptions into
> generators properly, when an external timer routine is used.
> The problem is that _lsprof.c: ptrace_enter_call assumes that there
> are no exceptions set when it is called, which is not true when the
> generator frame is being gen_send_ex'd to send an exception into it
> (Maybe you could say that only CallExternalTimer assumes this, but I
> am not sure).  This assumption causes its eventual call to
> CallExternalTimer to discover that an error is set and assume that it
> was caused by its own work (which it wasn't).
> I am not sure what the right way to fix this is, so I cannot send a patch.
> Here is a minimalist example to reproduce the bug:
>>>> import cProfile
>>>> import time
>>>> p=cProfile.Profile(time.clock)
>>>> def f():
> ...   yield 1
> ...
>>>> p.run("f().throw(Exception())")
> Exception exceptions.Exception: Exception() in <cProfile.Profile
> object at 0xb7f5a304> ignored
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
>   File "/usr/lib/python2.5/cProfile.py", line 135, in run
>     return self.runctx(cmd, dict, dict)
>   File "/usr/lib/python2.5/cProfile.py", line 140, in runctx
>     exec cmd in globals, locals
>   File "<string>", line 1, in <module>
>   File "<stdin>", line 1, in f
> SystemError: error return without exception set

There might be a similar problem with trace functions, see bug #1733757 which
is quite obscure too.


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