Re: [RFC PATCH v2] grep: allow for run time disabling of JIT in PCRE

> Hi,
>
> On Mon, 29 Jul 2019, Carlo Marcelo Arenas Belón wrote:
>
>>   $ git grep 'foo bar'
>>   fatal: Couldn't JIT the PCRE2 pattern 'foo bar', got '-48'
>
> My immediate reaction to this error message was: That's not helpful.
> What is `-48` supposed to mean? Why do we even think it sensible to
> throw such an error message at the end user? Can't we do a much better
> job translating that into something that makes actual sense without
> knowing implementation details?
>
> But then, I realized that -48 must be a well-known constant in PCRE2,
> and my reaction transformed into something much more hopeful: why don't
> we detect the situation where the JIT'ed code was not actually
> executable [*1*], and fall back to the non-JIT'ed code path ourselves,
> without troubling the end user (maybe warning, but maybe better not lest
> we annoy the user with something pointless)?
>
> Even after finding out that -48 disappointingly means
> PCRE2_ERROR_NOMEMORY (as opposed to something like
> PCRE2_ERROR_CANNOT_EXECUTE_JIT_CODE), I like the idea of not bothering
> end users and doing the sensible fallback under the hood.
>
> Ciao,
> Dscho
>
> Footnote *1*: Why anybody would think it sensible to build a PCRE2 with
> JIT on an OS that does not allow executing code that was written by the
> same process is beyond me. Or is there a mode in OpenBSD that *does*
> allow JIT'ed code to be executed?