Re: [RFC PATCH 2/2] grep: fallback to interpreter if JIT fails with pcre2

From: Junio C Hamano <gitster@pobox.com>
Date: Dec 10, 2018, 07:00 UTC
Message-ID: <xmqqh8flkgs2.fsf@gitster-ct.c.googlers.com>
In-Reply-To: <20181209230024.43444-3-carenas@gmail.com>

Carlo Marcelo Arenas Belón  <carenas@gmail.com> writes:

> starting with 10.23, and as a side effect of the work for bug1749[1] (grep
> -P crash with seLinux), pcre2grep was modified to ignore any errors from
> pcre2_jit_compile so the interpreter could be used as a fallback

That may (or may not---I do not know and I do not particularly feel the need to know or care about pcre2grep that is somebody else's project) describe what happened in the pcre2grep project, but it solicits a "so what?" response without the rest of the sentence you omitted.

I am guessing that the missing end of the sentence is "we should follow suit because ...", i.e. something like

    Starting from 10.23 [of what??? pcre2grep's version, libpcre's
    version, or something else???], pcre2grep falls back to
    interpreted pcre when JIT compilation fails.  We should follow
    suit in "git grep", because ...

Show 25 quoted lines

> [1] https://bugs.exim.org/show_bug.cgi?id=1749
>
> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
> ---
>  grep.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/grep.c b/grep.c
> index 5ccc0421a1..c751c8cc74 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -530,8 +530,11 @@ static void compile_pcre2_pattern(struct grep_pat *p, const struct grep_opt *opt
>  	pcre2_config(PCRE2_CONFIG_JIT, &p->pcre2_jit_on);
>  	if (p->pcre2_jit_on == 1) {
>  		jitret = pcre2_jit_compile(p->pcre2_pattern, PCRE2_JIT_COMPLETE);
> -		if (jitret)
> -			die("Couldn't JIT the PCRE2 pattern '%s', got '%d'\n", p->pattern, jitret);
> +		if (jitret) {
> +			/* JIT failed so fallback to the interpreter */
> +			p->pcre2_jit_on = 0;
> +			return;
> +		}
>  
>  		/*
>  		 * The pcre2_config(PCRE2_CONFIG_JIT, ...) call just