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From: Johannes Schindelin <Johannes.Schindelin@gmx.de>
To: "Carlo Marcelo Arenas Belón" <carenas@gmail.com>
Cc: git@vger.kernel.org, avarab@gmail.com,
	sandals@crustytoothpaste.net, gitster@pobox.com,
	dev+git@drbeat.li
Subject: Re: [RFC PATCH v2] grep: allow for run time disabling of JIT in PCRE
Date: Wed, 31 Jul 2019 14:32:16 +0200 (CEST)
Message-ID: <nycvar.QRO.7.76.6.1907311426290.21907@tvgsbejvaqbjf.bet> (raw)
In-Reply-To: <20190729105955.44390-1-carenas@gmail.com>

[-- Attachment #1: Type: text/plain, Size: 1382 bytes --]

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?

  parent reply	other threads:[~2019-07-31 12:32 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-28 23:54 [RFC PATCH] " Carlo Marcelo Arenas Belón
2019-07-29  0:09 ` Carlo Arenas
2019-07-29  4:57 ` Junio C Hamano
2019-07-29  5:29   ` Carlo Arenas
2019-07-29  8:55 ` Ævar Arnfjörð Bjarmason
2019-07-29 10:26   ` Carlo Arenas
2019-07-29 12:38     ` Ævar Arnfjörð Bjarmason
2019-07-30 13:01       ` Carlo Arenas
2019-07-29 10:59 ` [RFC PATCH v2] " Carlo Marcelo Arenas Belón
2019-07-29 11:33   ` Carlo Arenas
2019-07-29 15:11   ` René Scharfe
2019-07-29 17:47     ` Junio C Hamano
2019-07-30  0:49       ` Carlo Arenas
2019-07-30 17:55         ` René Scharfe
2019-07-31 12:36         ` Johannes Schindelin
2019-07-31 16:18           ` Junio C Hamano
2019-07-31 12:32   ` Johannes Schindelin [this message]
2019-07-31 14:57     ` Ævar Arnfjörð Bjarmason
2019-08-04  0:25       ` Carlo Arenas
2019-08-04  3:14   ` [RFC PATCH v3] grep: treat PCRE2 jit compilation memory error as non fatal Carlo Marcelo Arenas Belón
2019-08-04  7:43     ` Carlo Arenas
2019-08-05 20:16       ` Junio C Hamano
2019-07-31 12:24 ` [RFC PATCH] grep: allow for run time disabling of JIT in PCRE Johannes Schindelin

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