linux-kernel - Re: [PATCH 2/2] mkcompile_h: use printf for LINUX_COMPILE

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Date:   Tue, 17 Dec 2019 12:06:28 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mkcompile_h: use printf for LINUX_COMPILE_BY

On Fri, Dec 6, 2019 at 10:03 PM Masahiro Yamada <masahiroy@...nel.org> wrote:
>
> Commit 858805b336be ("kbuild: add $(BASH) to run scripts with
> bash-extension") shed light on portability issues. Here is another one.
>
> Since commit f07726048d59 ("Fix handling of backlash character in
> LINUX_COMPILE_BY name"), we must escape a backslash contained in
> LINUX_COMPILE_BY. This is not working on distros like Ubuntu.
>
> As the POSIX spec [1] says, if any of the operands contain a backslash
> ( '\' ) character, the results are implementation-defined.
>
> The actual shell of /bin/sh could be bash, dash depending on distros,
> and the behavior of builtin echo command is different among them.
>
> The bash builtin echo, unless -e is given, copies the arguments to
> output without expanding escape sequences (BSD-like behavior).
>
> The dash builtin echo, in contrast, adopts System V behavior, which
> does expand escape sequences without any option.
>
> Even non-builtin /bin/echo behaves differently depending on the system.
> Due to these variations, echo is considered as a non-portable command.
> Using printf is the common solution to avoid the portability issue.
>
> [1] https://pubs.opengroup.org/onlinepubs/009695399/utilities/echo.html
>
> Fixes: 858805b336be ("kbuild: add $(BASH) to run scripts with bash-extension")
> Reported-by: XXing Wei <xxing.wei@...soc.com>
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---

Applied to linux-kbuid.


>
>  scripts/mkcompile_h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
> index 3097fec1756a..3a5a4b210c86 100755
> --- a/scripts/mkcompile_h
> +++ b/scripts/mkcompile_h
> @@ -69,7 +69,7 @@ UTS_VERSION="$(echo $UTS_VERSION $CONFIG_FLAGS $TIMESTAMP | cut -b -$UTS_LEN)"
>
>    echo \#define UTS_VERSION \"$UTS_VERSION\"
>
> -  echo \#define LINUX_COMPILE_BY \"$LINUX_COMPILE_BY\"
> +  printf '#define LINUX_COMPILE_BY "%s"\n' "$LINUX_COMPILE_BY"
>    echo \#define LINUX_COMPILE_HOST \"$LINUX_COMPILE_HOST\"
>
>    echo \#define LINUX_COMPILER \"`$CC -v 2>&1 | grep ' version ' | sed 's/[[:space:]]*$//'`\"
> --
> 2.17.1
>


-- 
Best Regards
Masahiro Yamada