From: D. Ben Knoble <ben.knoble+github@gmail.com>
Date: Tue, 17 Feb 2026 13:38:00 GMT
Subject: Re: [PATCH v4] meson: regenerate config-list.h when Documentation changes
Message-ID: <CALnO6CBqbJ3s6XO0s_bTagJxT0N8nseyJb1T-H7+B6qqWNKoUg@mail.gmail.com>
In-Reply-To: <833b54f7-bb6b-4bb7-a5ec-fc0fa679abf8@gmail.com>

On Tue, Feb 17, 2026 at 4:20 AM Phillip Wood <phillip.wood123@gmail.com> wrote:
> On 16/02/2026 22:28, D. Ben Knoble wrote:
> > +if test -n "$DEPFILE"
> > +then
> > +     for doc in "$SOURCE_DIR"/Documentation/*config.adoc \
> > +             "$SOURCE_DIR"/Documentation/config/*.adoc
> > +     do
> > +             printf "$OUTPUT: %s\n" "$(printf '%s\n' "$doc" | sed 's/[# ]/\\&/g')"\\
>
> This forks two processes for every file which is a bit inefficient and
> will be especially slow on windows.

Yeah. I couldn't find a way I trusted to behave in the presence of
strange characters, though…

> If we quote $OUTPUT first we should
> be able to use a single sed process for all the files
>
>         QUOTED_OUTPUT="$(printf '%s\n' "$OUTPUT"| sed 's|[/\]|\\&|g')"
>         printf '%s\n' "$SOURCE_DIR"/Documentation/*config.adoc \
>                 "$SOURCE_DIR"/Documentation/config/*.adoc |
>         sed -e 's/[# ]/\\&/g' -e "s/^/$QUOTED_OUTPUT: /" >"$DEPFILE"

…and this version matches a concept I considered. Let me think aloud.

To quote output, we backslash-escape any "/" and "\"; we are going to
use it in the replacement side of sed's substitute command with "/"
delimiters.

My manual says "&" and "\[0-9]" are also special in the replacement
string. We have no backreferences for the latter, but my sed on macOS
complains about bad backreferences in cases like

    echo abc | sed 's/^/foo\1/'

OTOH, escaping backslashes already covers such backreferences. So I
think we'd need something closer to

    sed 's,[&/\],\\&,g'

? If you agree with that reasoning, I'll include this in the next
version. (I'll also try this out a bit first.)

PS in patterns with so many "vertical" characters, I find the commas a
bit easier to read than pipes :)