linux-kernel - Re: [PATCH v3] scripts/setlocalversion: fix a bug when LOCALVERSION is empty

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Date:   Mon, 12 Jul 2021 23:17:35 +0200
From:   Nico Schottelius <nico-linuxsetlocalversion@...ottelius.org>
To:     Mikulas Patocka <mpatocka@...hat.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nico Schottelius <nico-linuxsetlocalversion@...ottelius.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] scripts/setlocalversion: fix a bug when LOCALVERSION
 is empty


Sorry to say, but I am not convinced by the patch.

While yes, we might have changed the behaviour slightly, reading
something on the line of

if [ -z ... ]

is significantly more simple, elegant and easier to maintain, than
a rather atypical special case for setting a variable to empty,
using

if [ "${LOCALVERSION+set}" != "set" ] ..

*and* because it is so atypical, adding a long comment for it, too.

Additonally, -z should be correct if the variable *is* truly empty. I
assume it actually isn't and contains whitespace, which is not the same
as being set and empty.

Instead of re-adding complexity, could you consider changing the build
flow so that LOCALVERSION is either unset or empty?

Nico

Executed in bash:

% touch empty
% a=$(cat empty)
% [ -z "$a" ]  && echo "really empty"
really empty


Mikulas Patocka <mpatocka@...hat.com> writes:

> On Mon, 12 Jul 2021, Greg Kroah-Hartman wrote:
>
>> On Mon, Jul 12, 2021 at 03:06:48PM -0400, Mikulas Patocka wrote:
>> >
>> >
>> > On Mon, 12 Jul 2021, Greg Kroah-Hartman wrote:
>> >
>> > > On Mon, Jul 12, 2021 at 10:00:59AM -0400, Mikulas Patocka wrote:
>> > > > The patch 042da426f8ebde012be9429ff705232af7ad7469
>> > > > ("scripts/setlocalversion: simplify the short version part") reduces the
>> > > > indentation. Unfortunatelly, it also changes behavior in a subtle way - if
>> > > > the user has empty "LOCALVERSION" variable, the plus sign is appended to
>> > > > the kernel version. It wasn't appended before.
>> > > >
>> > > > This patch reverts to the old behavior - we append the plus sign only if
>> > > > the LOCALVERSION variable is not set.
>> > > >
>> > > > Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
>> > > > Fixes: 042da426f8eb ("scripts/setlocalversion: simplify the short version part")
>> > > >
>> > > > ---
>> > > >  scripts/setlocalversion |    2 +-
>> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
>> > > >
>> > > > Index: linux-2.6/scripts/setlocalversion
>> > > > ===================================================================
>> > > > --- linux-2.6.orig/scripts/setlocalversion	2021-07-12 15:29:07.000000000 +0200
>> > > > +++ linux-2.6/scripts/setlocalversion	2021-07-12 15:50:29.000000000 +0200
>> > > > @@ -131,7 +131,7 @@ res="${res}${CONFIG_LOCALVERSION}${LOCAL
>> > > >  if test "$CONFIG_LOCALVERSION_AUTO" = "y"; then
>> > > >  	# full scm version string
>> > > >  	res="$res$(scm_version)"
>> > > > -elif [ -z "${LOCALVERSION}" ]; then
>> > > > +elif [ "${LOCALVERSION+set}" != "set" ]; then
>> > >
>> > > That's really subtle, can you add a comment here that this handles an
>> > > empty file?
>> > >
>> > > thanks,
>> > >
>> > > greg k-h
>> >
>> > OK.
>> >
>> >
>> > From: Mikulas Patocka <mpatocka@...hat.com>
>> >
>>
>> I can't take a patch like this :(
>>
>> > The patch 042da426f8ebde012be9429ff705232af7ad7469
>> > ("scripts/setlocalversion: simplify the short version part") reduces
>>
>> Properly quote commits, the documentation says you do not need to use
>> the full sha1.
>
>
>
> From: Mikulas Patocka <mpatocka@...hat.com>
>
> The commit 042da426f8eb ("scripts/setlocalversion: simplify the short
> version part") reduces indentation. Unfortunately, it also changes behavior
> in a subtle way - if the user has empty "LOCALVERSION" variable, the plus
> sign is appended to the kernel version. It wasn't appended before.
>
> This patch reverts to the old behavior - we append the plus sign only if
> the LOCALVERSION variable is not set.
>
> Signed-off-by: Mikulas Patocka <mpatocka@...hat.com>
> Fixes: 042da426f8eb ("scripts/setlocalversion: simplify the short version part")
>
> ---
>  scripts/setlocalversion |   13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> Index: linux-2.6/scripts/setlocalversion
> ===================================================================
> --- linux-2.6.orig/scripts/setlocalversion	2021-07-12 15:29:07.000000000 +0200
> +++ linux-2.6/scripts/setlocalversion	2021-07-12 21:00:59.000000000 +0200
> @@ -131,11 +131,14 @@ res="${res}${CONFIG_LOCALVERSION}${LOCAL
>  if test "$CONFIG_LOCALVERSION_AUTO" = "y"; then
>  	# full scm version string
>  	res="$res$(scm_version)"
> -elif [ -z "${LOCALVERSION}" ]; then
> -	# append a plus sign if the repository is not in a clean
> -	# annotated or signed tagged state (as git describe only
> -	# looks at signed or annotated tags - git tag -a/-s) and
> -	# LOCALVERSION= is not specified
> +elif [ "${LOCALVERSION+set}" != "set" ]; then
> +	# If the variable LOCALVERSION is not set, append a plus
> +	# sign if the repository is not in a clean annotated or
> +	# signed tagged state (as git describe only looks at signed
> +	# or annotated tags - git tag -a/-s).
> +	#
> +	# If the variable LOCALVERSION is set (including being set
> +	# to an empty string), we don't want to append a plus sign.
>  	scm=$(scm_version --short)
>  	res="$res${scm:++}"
>  fi


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