Re: [PATCH] config: remove explicit undef of unset values

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, Jun 13, 2022 at 02:26:14PM +0200, David Marchand wrote:
> On Mon, Jun 13, 2022 at 11:54 AM Bruce Richardson
> <bruce.richardson@intel.com> wrote:
> > On Thu, Dec 16, 2021 at 11:14:30AM +0000, Bruce Richardson wrote:
> > > Rather than explicitly clearing any setting of undefined values in our
> > > rte_config.h file, it's better to instead just add a comment that the
> > > value is not set. Using a comment allows the user to set the value using
> > > CFLAGS or similar mechanism without the config file clearing the value
> > > again.
> > >
> > > The text used "<VALUE> is not set" is modelled after the kernel approach
> > > of doing the same thing.
> > >
> > > Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> > > ---
> > >
> > > Although DPDK coding convention forbids use of "//" for comments, using
> > > regular C comment style makes the config settings less clear, as they can
> > > be confused with regular comments in the file. Using "//" makes them stand
> > > out better, so I prefer it. However, if others feel strongly, they can be
> > > changed to standard.
> > >
> > > Note: this is a resubmission of patch [1] which was part of a rejected
> > > series. However, the reasons for rejection - values in config being out
> > > of sync with those used for building apps - are less relevant for
> > > many, if not all, of these setting, so I believe the benefits for
> > > testing outweigh the potential downsides. If any setting is likely
> > > problematic, I can keep the explicit undef for that case in a new patch
> > > version.
> > >
> > > [1] http://patches.dpdk.org/project/dpdk/patch/20200903144942.671870-2-bruce.richardson@intel.com/
> > > ---
> >
> > Ping for review or feedback for this patch. I'd like to see it move forward
> > into a DPDK release if possible.
> 
> I'd like a check like (below), to avoid new additions:
> 
> diff --git a/devtools/checkpatches.sh b/devtools/checkpatches.sh
> index 34a2e43845..8dae47165e 100755
> --- a/devtools/checkpatches.sh
> +++ b/devtools/checkpatches.sh
> @@ -158,6 +158,14 @@ check_forbidden_additions() { # <patch>
>                 -f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
>                 "$1" || res=1
> 
> +       # '// XXX is not set' must be preferred over '#undef XXX'
> +       awk -v FOLDERS='config/rte_config.h' \
> +               -v EXPRESSIONS='#undef' \
> +               -v RET_ON_FAIL=1 \
> +               -v MESSAGE='Using "#undef XXX", prefer "// XXX is not set"' \
> +               -f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
> +               "$1" || res=1
> +
>         return $res
>  }
> 
> Otherwise, the change lgtm.
> 
Good idea. Do you want me to add your check above as a patch to this to
make a two-patch set for v2?

/Bruce