Subject: Re: [PATCH 21/29] grep: factor test for \0 in grep patterns into a function

From: Brandon Williams <[email-masked]>
Date: Thu, 11 May 2017 13:15:17 -0700

On 05/11, Ævar Arnfjörð Bjarmason wrote:
> Factor the test for \0 in grep patterns into a function. Since commit
> 9eceddeec6 ("Use kwset in grep", 2011-08-21) any pattern containing a
> \0 is considered fixed as regcomp() can't handle it.
> 
> This limitation was never documented, and other some regular
> expression engines are capable of compiling a pattern containing a
> \0. Factoring this out makes a subsequent change which does that
> smaller.
> 
> See a previous commit in this series ("grep: add tests to fix blind
> spots with \0 patterns", 2017-04-21) for further details & rationale.
> 
> Signed-off-by: Ævar Arnfjörð Bjarmason <[email-masked]>
> ---
>  grep.c | 19 ++++++++++++-------
>  1 file changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/grep.c b/grep.c
> index bf6c2494fd..27de615209 100644
> --- a/grep.c
> +++ b/grep.c
> @@ -394,12 +394,6 @@ static int is_fixed(const char *s, size_t len)
>  {
>  	size_t i;
>  
> -	/* regcomp cannot accept patterns with NULs so we
> -	 * consider any pattern containing a NUL fixed.
> -	 */
> -	if (memchr(s, 0, len))
> -		return 1;
> -
>  	for (i = 0; i < len; i++) {
>  		if (is_regex_special(s[i]))
>  			return 0;
> @@ -408,6 +402,17 @@ static int is_fixed(const char *s, size_t len)
>  	return 1;
>  }
>  
> +static int has_null(const char *s, size_t len)
> +{
> +	/* regcomp cannot accept patterns with NULs so when using it
> +	 * we consider any pattern containing a NUL fixed.
> +	 */

I commented on a later patch but really the comment should be fixed
here.  And why not simply move this to where you intend it to be at the
end of the series now?

> +	if (memchr(s, 0, len))
> +		return 1;
> +
> +	return 0;
> +}
> +
>  static void compile_fixed_regexp(struct grep_pat *p, struct grep_opt *opt)
>  {
>  	struct strbuf sb = STRBUF_INIT;
> @@ -451,7 +456,7 @@ static void compile_regexp(struct grep_pat *p, struct grep_opt *opt)
>  	 * simple string match using kws.  p->fixed tells us if we
>  	 * want to use kws.
>  	 */
> -	if (opt->fixed || is_fixed(p->pattern, p->patternlen))
> +	if (opt->fixed || has_null(p->pattern, p->patternlen) || is_fixed(p->pattern, p->patternlen))
>  		p->fixed = !icase || ascii_only;
>  	else
>  		p->fixed = 0;
> -- 
> 2.11.0
> 

-- 
Brandon Williams