I created https://bugs.python.org/issue47185 to discuss this issue:
either recompute automatically co_exceptiontable, or at least document
the change.
Victor
On Fri, Apr 1, 2022 at 11:21 AM Victor Stinner <vstin...@python.org> wrote:
>
> ("Re: C API: Move PEP 523 "Adding a frame evaluation API to CPython"
> private C API to the internal C API")
>
> On Fri, Apr 1, 2022 at 11:01 AM Chris Angelico <ros...@gmail.com> wrote:
> >
> > On Fri, 1 Apr 2022 at 19:51, Victor Stinner <vstin...@python.org> wrote:
> > > In Python, sadly the types.CodeType type also has a public constructor
> > > and many projects break at each Python release because the API
> > > changes. Hopefully, it seems like the new CodeType.replace() method
> > > added to Python 3.8 mitigated the issue. IMO CodeType.replace() is a
> > > better abstraction and closer to what developers need in practice.
> >
> > It certainly has been for me. When I want to do bytecode hackery, I
> > usually start by creating a function with def/lambda, then construct a
> > modified function using f.__code__.replace(). It's the easiest way to
> > ensure that all the little details are correct.
>
> Python 3.11 added the concept of "exception table"
> (code.co_exceptiontable). You have to build this table, otherwise
> Python can no longer catch exceptions :-)
>
> I don't know how to build this exception table. It seems like
> currently there is no Python function in the stdlib to build this
> table.
>
> Example:
> ---
> def f():
> try:
> print("raise")
> raise ValueError
> except ValueError:
> print("except")
> else:
> print("else")
> print("exit func")
>
> def g(): pass
>
> if 1:
> code = f.__code__
> g.__code__ = g.__code__.replace(
> co_code=code.co_code,
> co_consts=code.co_consts,
> co_names=code.co_names,
> co_flags=code.co_flags,
> co_stacksize=code.co_stacksize)
> else:
> g.__code__ = f.__code__ # this code path works on Python 3.11
>
> g()
> ---
>
> Output with Python 3.10 (ok):
> ---
> raise
> except
> exit func
> ---
>
> Output with Python 3.11 (oops):
> ---
> raise
> Traceback (most recent call last):
> ...
> ValueError
> ---
>
> By the way, this change is not documented at all:
>
> * https://docs.python.org/dev/library/types.html#types.CodeType
> * https://docs.python.org/dev/whatsnew/3.11.html
>
> I understand that these changes come from the "Zero cost exception
> handling" change:
> https://bugs.python.org/issue40222
>
> Victor
> --
> Night gathers, and now my watch begins. It shall not end until my death.
--
Night gathers, and now my watch begins. It shall not end until my death.
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