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

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Message-ID: <CAK7LNARCRQ_K=4vAQxgQiq_w8ss5+uhGnY1L7nre=H3eWeq6zA@mail.gmail.com>
Date: Tue, 13 Aug 2024 00:44:40 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Max Krummenacher <max.oss.09@...il.com>
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 Mon, Aug 12, 2024 at 11:58 PM Max Krummenacher <max.oss.09@...il.com> wrote:
>
> 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.


You cannot.

Your buggy commit already landed in Linus' tree:

https://github.com/torvalds/linux/commit/6e20753da6bc651e02378a0cdb78f16c42098c88





> >
> > 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.



You do not need to educate me.

It is well described in commit 3bd85c6c97b2d232638594bf828de62083fe3389
and I know how it works.



> >
> > 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.



See my patch closely.

I deleted the line "* conmakehash %s > [this file]\n\"









> 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
> >



--
Best Regards

Masahiro Yamada