linux-kernel - Re: [PATCH] scripts/kernel-doc: Fix the regex for matching -Werror flag

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Date:   Mon, 30 Oct 2023 10:53:12 -0600
From:   Jonathan Corbet <corbet@....net>
To:     Yujie Liu <yujie.liu@...el.com>, linux-doc@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Swarup Laxman Kotiaklapudi <swarupkotikalapudi@...il.com>,
        Akira Yokosawa <akiyks@...il.com>
Subject: Re: [PATCH] scripts/kernel-doc: Fix the regex for matching -Werror
 flag

Yujie Liu <yujie.liu@...el.com> writes:

> Swarup reported a "make htmldocs" warning:
>
>   Variable length lookbehind is experimental in regex;
>   marked by <-- HERE in m/(?<=^|\s)-Werror(?=$|\s)
>   <-- HERE / at ./scripts/kernel-doc line 188.
>
> Akira managed to reproduce it by perl v5.34.0.
>
> On second thought, it is not necessary to have the complicated
> "lookahead and lookbehind" things, and the regex can be simplified.
>
> Generally, the kernel-doc warnings should be considered as errors only
> when "-Werror" flag is set in KCFLAGS, but not when
> "-Werror=<diagnostic-type>" is set, which means there needs to be a
> space or start of string before "-Werror", and a space or end of string
> after "-Werror".
>
> The following cases have been tested to work as expected:
>
> * kernel-doc warnings are considered as errors:
>
>   $ KCFLAGS="-Werror" make W=1
>   $ KCFLAGS="-Wcomment -Werror" make W=1
>   $ KCFLAGS="-Werror -Wundef" make W=1
>   $ KCFLAGS="-Wcomment -Werror -Wundef" make W=1
>
> * kernel-doc warnings remain as warnings:
>
>   $ KCFLAGS="-Werror=return-type" make W=1
>   $ KCFLAGS="-Wcomment -Werror=return-type" make W=1
>   $ KCFLAGS="-Werror=return-type -Wundef" make W=1
>   $ KCFLAGS="-Wcomment -Werror=return-type -Wundef" make W=1
>
> The "Variable length lookbehind is experimental in regex" warning is
> also resolved by this patch.
>
> Fixes: 91f950e8b9d8 ("scripts/kernel-doc: match -Werror flag strictly")
> Reported-by: Swarup Laxman Kotiaklapudi <swarupkotikalapudi@...il.com>
> Cc: Akira Yokosawa <akiyks@...il.com>
> Signed-off-by: Yujie Liu <yujie.liu@...el.com>
> ---
>  scripts/kernel-doc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/kernel-doc b/scripts/kernel-doc
> index d660e1f4b483..08a3e603db19 100755
> --- a/scripts/kernel-doc
> +++ b/scripts/kernel-doc
> @@ -185,7 +185,7 @@ if (defined($ENV{'KBUILD_VERBOSE'}) && $ENV{'KBUILD_VERBOSE'} =~ '1') {
>  if (defined($ENV{'KCFLAGS'})) {
>  	my $kcflags = "$ENV{'KCFLAGS'}";
>  
> -	if ($kcflags =~ /(?<=^|\s)-Werror(?=$|\s)/) {
> +	if ($kcflags =~ /(\s|^)-Werror(\s|$)/) {
>  		$Werror = 1;

OK, I've applied this one and will sneak it into the 6.7 pull request,
thanks.

jon