[Python-ideas] Changes to the existing optimization levels

[Diana Clarke]

In the mean time, I've re-opened the following pull request that can
be merged independent of these changes (it's just additional test
coverage).

    trivial: add test coverage for the __debug__ case (optimization levels)
    https://github.com/python/cpython/pull/3450

Please let me know if I should create a bpo for it, if the commit
message is too long, or if you think I should otherwise change the
patch in any way.

As always, thanks for your time folks!

--diana

On Fri, Sep 29, 2017 at 2:24 PM, Diana Clarke
<diana.joan.clarke at gmail.com> wrote:
> Oh, I like this idea!
>
> I had very briefly considered treating the existing flag as a
> bitfield, but then promptly forgot to explore that line of thought
> further.
>
> I'll play with that approach next week, see where it takes me, and
> then report back.
>
> Thanks so much for taking the time to think this through with me –
> much appreciated.
>
> Cheers,
>
> --diana
>
> On Fri, Sep 29, 2017 at 1:33 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:
>> 2. We could reinterpret "optimize" as a bitfield instead of a regular
>> integer, special casing the already defined values:
>>
>> - all zero: no optimizations
>> - sign bit set: negative -> use global settings
>> - 0x0001: nodebug+noassert
>> - 0x0002: nodebug+noassert+nodocstrings
>> - 0x0004: nodebug
>> - 0x0008: noassert
>> - 0x0010: nodocstrings
>>
>> The "redefine optimizations as a bitfield" approach seems particularly
>> promising to me - it's a full integer, so even with all negative
>> numbers disallowed and the two low order bits reserved for the legacy
>> combinations, that's still 29 different optimisation flags given
>> 32-bit integers. We currently have 3, so that's room for an 866%
>> increase in the number of defined flags :)