Re: [PATCH v2] grep: fall back to interpreter if JIT memory allocation fails

> Junio C Hamano <gitster@pobox.com> writes:
> 
>> If we were to keep that "die", it is absolutely required, I would
>> think.  Users who got their Git with JIT-enabled pcre2 may be
>> viewing JIT merely as "a clever optimization the implementation is
>> allowed to use when able", without knowing and more importantly
>> without wanting to know how to disable it from within their
>> patterns.
>>
>> But can't we drop that die() if we took the v1 route?
> 
> Having said all that, I do not mind queuing v2 if the "use *NO_JIT
> to disable" is added to the message to help users who are forced to
> redo the query.
> 
> And in practice, it shouldn't make that much difference, because the
> only scenario (other than the SELinux-like situation where JIT is
> compiled in but does not work at all) that the difference may matter
> would happen when a non-trivial portion of the patterns users use
> are not workable with JIT, but if that were the case, we would have
> written JIT off as not mature enough and not yet usable long time
> ago.  So, in practice, patterns refused by JIT would be a very tiny
> minority to matter in real life, and "failing fast to inconvenience
> users" would not be too bad.

> So while I still think v1's simplicity is the right thing to have
> here, I think it is waste of our braincell to compare v1 vs v2.  As
> v2 gives smaller incremental behaviour change perceived by end
> users, if somebody really wanted to, I'd expect that a low-hanging
> fruit #leftoverbit on top of such a patch, after the dust settles,
> would be to
> 
>  (1) rename pcre2_jit_functional() to fall_back_to_interpreter() or
>      something,
> 
>  (2) add a configuration variable to tell fall_back_to_interpreter()
>      that any form of JIT error is allowed to fall back to
>      interpreter().
> 
> and such a patch will essentially give back the simplicity of v1 to
> folks who opt into the configuration.