[Python-Dev] Add a developer mode to Python: -X dev command line option

Nick Coghlan ncoghlan at gmail.com
Thu Nov 16 08:05:35 EST 2017

On 16 November 2017 at 22:54, Antoine Pitrou <antoine at python.org> wrote:

> Hi Victor,
> Thanks for the answer!
> Le 16/11/2017 à 13:48, Victor Stinner a écrit :
> >
> > faulthandler has a negligible cost on performance/memory.
> >
> > For -W default, I guess that your question is the cost on emitting a
> > warning: overhead when a warning is displayed, and overhead when the
> > warning is filtered. Right?
> -Wdefault means -Wonce or -Walways? If the former, I don't expect many
> warnings to be emitted.

Confusingly, neither of these: default, once, module, and always are all
different settings.

once: once per process (regardless of location)
module: once per module (regardless of line)
default: once per location (line+module combination)
always: every time

Still, even with once-per-location behaviour, the warning overhead should
be minimal.


Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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