[issue29096] Signal Handlers reliably cause UnboundLocalErrors

[Joe Jevnik]

Joe Jevnik added the comment:

The issue appears to be in ceval.c:unicode_concatenate (or the py2 equivalent)

The code sets the local variable on the lhs to NULL before doing a potentially inplace append to the string. This means that if a signal is raised during the concat, we never hit the STORE_FAST instruction following the INPLACE_ADD so the local or cell still holds NULL, triggering an error.

I am not really sure what can be done to prevent the failure while still allowing the optimization.

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components: +Interpreter Core
nosy: +llllllllll
type: crash -> 

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29096>
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