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

["René Scharfe" <l.s.r@web.de>]

Am 29.07.19 um 12:59 schrieb Carlo Marcelo Arenas Belón:
> PCRE1 allowed for a compile time flag to disable JIT, but PCRE2 never
> had one, forcing the use of JIT if -P was requested.
>
> After ed0479ce3d (Merge branch 'ab/no-kwset' into next, 2019-07-15)
> the PCRE2 engine will be used more broadly and therefore adding this
> knob will allow users a escape from situations where JIT might be
> problematic.
>
> JIT will be used by default but it can be disabled with the --no-pcre-jit
> option in `git grep` or by setting 0/false into the pcre.jit config.
>
> If a value of -1 is used instead then the following error is prevented by
> using the interpreter when a JIT failure consistent with known security
> restrictions is found at regex compilation time.
>
>   $ git grep 'foo bar'
>   fatal: Couldn't JIT the PCRE2 pattern 'foo bar', got '-48'
>
> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
> ---
> V2: add command line to grep as suggested by Junio
>
>  Documentation/git-grep.txt | 11 +++++++++++
>  builtin/grep.c             |  4 ++++
>  grep.c                     | 30 ++++++++++++++++++++++++++----
>  grep.h                     |  1 +
>  4 files changed, 42 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
> index c89fb569e3..895c6b34ec 100644
> --- a/Documentation/git-grep.txt
> +++ b/Documentation/git-grep.txt
> @@ -13,6 +13,7 @@ SYNOPSIS
>  	   [-v | --invert-match] [-h|-H] [--full-name]
>  	   [-E | --extended-regexp] [-G | --basic-regexp]
>  	   [-P | --perl-regexp]
> +	   [-j | --[no]-pcre-jit]

Do users care?  Enough so to add a short option for this?

>  	   [-F | --fixed-strings] [-n | --line-number] [--column]
>  	   [-l | --files-with-matches] [-L | --files-without-match]
>  	   [(-O | --open-files-in-pager) [<pager>]]
> @@ -69,6 +70,12 @@ grep.fallbackToNoIndex::
>  	If set to true, fall back to git grep --no-index if git grep
>  	is executed outside of a git repository.  Defaults to false.
>
> +pcre.jit::
> +	If set to false, disable JIT when using PCRE.  Defaults to
> +	true.
> +	if set to -1 will try first to use JIT and fallback to the
> +	interpreter instead of returning an error.

Why not implement only -1, without adding this config setting?

> +
>
>  OPTIONS
>  -------
> @@ -175,6 +182,10 @@ providing this option will cause it to die.
>  	Use fixed strings for patterns (don't interpret pattern
>  	as a regex).
>
> +-j::
> +--[no-]pcre-jit::
> +	Diable JIT in PCRE with --no-pcre-jit.

"Disable".

René