[Python-Dev] Is core dump always a bug? Advice requested (original) (raw)

Tim Peters tim.one at comcast.net
Thu May 13 15:32:30 EDT 2004

[Michel Pelletier]

But just looking at some code here, is RETURNVALUE ever inside a SETUPEXCEPT block? The end of the SETUPEXCEPT block apears to ABSOLUTEJUMP past all the exception handlers to finally, and then to the RETURNVALUE, which doesn't seem to fall under the protection of a try/except.

I don't think I can understand what you're saying without a concrete example. Here's one:

""" def f(): try: return 42 finally: print 'yup'

from dis import dis dis(f) """

That displays:

""" 2 0 SETUP_FINALLY 8 (to 11)

3 3 LOAD_CONST 1 (42) 6 RETURN_VALUE 7 POP_BLOCK 8 LOAD_CONST 0 (None)

4 >> 11 LOAD_CONST 2 ('yup')

5 14 PRINT_ITEM 15 PRINT_NEWLINE 16 END_FINALLY 17 LOAD_CONST 0 (None) 20 RETURN_VALUE """

The RETURN_VALUE at 6 doesn't return right away, although that's not obvious from the byte code. The code at 11, 14, 15, 16 executes first, and that can't be guessed from staring at 6 in isolation. I think the code at 7, 8, 17 and 20 is actually unreachable -- and that's so not obvious I had to say "I think" .

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