[Python-Dev] Consolidate stateful runtime globals

[Gregory P. Smith]

On Wed, Sep 6, 2017 at 10:26 AM Benjamin Peterson <benjamin at python.org>
wrote:

>
> On Wed, Sep 6, 2017, at 10:08, Antoine Pitrou wrote:
> > On Wed, 06 Sep 2017 09:42:29 -0700
> > Benjamin Peterson <benjamin at python.org> wrote:
> > > On Wed, Sep 6, 2017, at 03:14, Antoine Pitrou wrote:
> > > >
> > > > Hello,
> > > >
> > > > I'm a bit concerned about
> > > >
> https://github.com/python/cpython/commit/76d5abc8684bac4f2fc7cccfe2cd940923357351
> > > >
> > > > My main gripe is that makes writing C code more tedious.  Simple C
> > > > global variables such as "_once_registry" are now spelled
> > > > "_PyRuntime.warnings.once_registry".  The most egregious example
> seems
> > > > to be "_PyRuntime.ceval.gil.locked" (used to be simply "gil_locked").
> > > >
> > > > Granted, C is more verbose than Python, but it doesn't have to become
> > > > that verbose.  I don't know about you, but when code becomes annoying
> > > > to type, I tend to try and take shortcuts.
> > >
> > > How often are you actually typing the names of runtime globals, though?
> >
> > Not very often, but if I want to experiment with some low-level
> > implementation details, it is nice to avoid the hassle.
>
> It seems like this could be remediated with some inline functions or
> macros, which would also help safely encapsulate state.
>
> >
> > There's also a readability argument: with very long names, expressions
> > can become less easy to parse.
> >
> > > If you are using a globals, perhaps the typing time will allow you to
> > > fully consider the gravity of the situation.
> >
> > Right, I needed to be reminded of how perilous the use of C globals is.
> > Perhaps I should contact the PSRT the next time I contemplate using a C
> > global.
>
> It's not just you but future readers.
>

I'm not concerned about moving things into a state structure rather than
wildly scattered globals declared all over the place.  It is good code
hygiene. It ultimately moves us closer (much more work to be done) to being
able to actually have multiple independent interpreters within the same
process (including potentially even of different Python versions).

For commonly typed things that get annoying,

#define _Py_grail   _PyRuntme.ceval.holy.grail

within the .c source file that does a lot of grail flinging seems fine to
me.

-gps
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