linux-kernel - Re: [PATCH] tty: vt: conmakehash: remove non-portable code printing comment header

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Message-ID: <ZrojDUbr1EvlARXK@toolbox>
Date: Mon, 12 Aug 2024 16:58:21 +0200
From: Max Krummenacher <max.oss.09@...il.com>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kbuild@...r.kernel.org,
	Max Krummenacher <max.krummenacher@...adex.com>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Daniel Gomez <da.gomez@...sung.com>,
	Jiri Slaby <jirislaby@...nel.org>, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH] tty: vt: conmakehash: remove non-portable code printing
 comment header

On Sat, Aug 10, 2024 at 01:07:20AM +0900, Masahiro Yamada wrote:
> Commit 6e20753da6bc ("tty: vt: conmakehash: cope with abs_srctree no
> longer in env") included <linux/limits.h>, which invoked another
> (wrong) patch that tried to address a build error on macOS.
> 
> According to the specification [1], the correct header to use PATH_MAX
> is <limits.h>.
> 
> The minimal fix would be to replace <linux/limits.h> with <limits.h>.
I can change that in a v2.

> 
> However, the following commits seem questionable to me:
> 
>  - 3bd85c6c97b2 ("tty: vt: conmakehash: Don't mention the full path of the input in output")
>  - 6e20753da6bc ("tty: vt: conmakehash: cope with abs_srctree no longer in env")
> 
> These commits made too many efforts to cope with a comment header in
> drivers/tty/vt/consolemap_deftbl.c:
> 
>   /*
>    * Do not edit this file; it was automatically generated by
>    *
>    * conmakehash drivers/tty/vt/cp437.uni > [this file]
>    *
>    */

This is the output you get when keeping the build artifacts within the
linux source tree.
However if you keep the artifacts outside the source tree
(make O=/somepath ...) the output looks like this:

    /*
     * Do not edit this file; it was automatically generated by
     *
     * conmakehash /path-to-kernel-source-tree/drivers/tty/vt/cp437.uni > [this file]
     *
     */

i.e. it does keep a reference to where in your filesystem the kernel
source did reside when building which is against the goal of having a
reproducable build.

> 
> With this commit, the header part of the generate C file will be
> simplified as follows:
> 
>   /*
>    * Automatically generated file; Do not edit.
>    */

This is not what I observed, for me with this proposed commit the
comment becomes with or without the 'O=somepath':

    /*
     * Do not edit this file; it was automatically generated by
     *
     * conmakehash cp437.uni > [this file]
     *
     */

i.e. it strips the directory path of the chartable source file used.

Regards
Max

> 
> BTW, another series of excessive efforts for a comment header can be
> seen in the following:
> 
>  - 5ef6dc08cfde ("lib/build_OID_registry: don't mention the full path of the script in output")
>  - 2fe29fe94563 ("lib/build_OID_registry: avoid non-destructive substitution for Perl < 5.13.2 compat")
> 
> [1]: https://pubs.opengroup.org/onlinepubs/009695399/basedefs/limits.h.html
> 
> Fixes: 6e20753da6bc ("tty: vt: conmakehash: cope with abs_srctree no longer in env")
> Reported-by: Daniel Gomez <da.gomez@...sung.com>
> Closes: https://lore.kernel.org/all/20240807-macos-build-support-v1-11-4cd1ded85694@samsung.com/
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
> 
>  drivers/tty/vt/conmakehash.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/tty/vt/conmakehash.c b/drivers/tty/vt/conmakehash.c
> index 82d9db68b2ce..a931fcde7ad9 100644
> --- a/drivers/tty/vt/conmakehash.c
> +++ b/drivers/tty/vt/conmakehash.c
> @@ -11,8 +11,6 @@
>   * Copyright (C) 1995-1997 H. Peter Anvin
>   */
>  
> -#include <libgen.h>
> -#include <linux/limits.h>
>  #include <stdio.h>
>  #include <stdlib.h>
>  #include <sysexits.h>
> @@ -79,7 +77,6 @@ int main(int argc, char *argv[])
>  {
>    FILE *ctbl;
>    const char *tblname;
> -  char base_tblname[PATH_MAX];
>    char buffer[65536];
>    int fontlen;
>    int i, nuni, nent;
> @@ -245,20 +242,15 @@ int main(int argc, char *argv[])
>    for ( i = 0 ; i < fontlen ; i++ )
>      nuni += unicount[i];
>  
> -  strncpy(base_tblname, tblname, PATH_MAX);
> -  base_tblname[PATH_MAX - 1] = 0;
>    printf("\
>  /*\n\
> - * Do not edit this file; it was automatically generated by\n\
> - *\n\
> - * conmakehash %s > [this file]\n\
> - *\n\
> + * Automatically generated file; Do not edit.\n\
>   */\n\
>  \n\
>  #include <linux/types.h>\n\
>  \n\
>  u8 dfont_unicount[%d] = \n\
> -{\n\t", basename(base_tblname), fontlen);
> +{\n\t", fontlen);
>  
>    for ( i = 0 ; i < fontlen ; i++ )
>      {
> -- 
> 2.43.0
>