linux-kernel - Re: [PATCH v2] modpost: remove use of non-standard strsep() in HOSTCC code

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Message-ID: <CAK7LNASY18tKarE8gtmRd8o9uRPtF-7QAh_CLwrj8yvT_fEi0Q@mail.gmail.com>
Date:   Thu, 2 Jul 2020 00:50:27 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: [PATCH v2] modpost: remove use of non-standard strsep() in HOSTCC code

On Wed, Jul 1, 2020 at 3:18 PM H. Nikolaus Schaller <hns@...delico.com> wrote:
>
> strsep() is neither standard C nor POSIX and used outside
> the kernel code here. Using it here requires that the
> build host supports it out of the box which is e.g.
> not true for a Darwin build host and using a cross-compiler.
> This leads to:
>
> scripts/mod/modpost.c:145:2: warning: implicit declaration of function 'strsep' [-Wimplicit-function-declaration]
>   return strsep(stringp, "\n");
>   ^
>
> and a segfault when running MODPOST.
>
> See also: https://stackoverflow.com/a/7219504
>
> So let's replace this by strchr() instead of using strsep().
> It does not hurt kernel size or speed since this code is run
> on the build host.
>
> Fixes: ac5100f5432967 ("modpost: add read_text_file() and get_line() helpers")
> Co-developed-by: Masahiro Yamada <masahiroy@...nel.org>
> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
> ---

Applied to linux-kbuild.
Thanks.


>  scripts/mod/modpost.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 6aea65c657454..45f2ab2ec2d46 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -138,11 +138,19 @@ char *read_text_file(const char *filename)
>
>  char *get_line(char **stringp)
>  {
> +       char *orig = *stringp, *next;
> +
>         /* do not return the unwanted extra line at EOF */
> -       if (*stringp && **stringp == '\0')
> +       if (!orig || *orig == '\0')
>                 return NULL;
>
> -       return strsep(stringp, "\n");
> +       next = strchr(orig, '\n');
> +       if (next)
> +               *next++ = '\0';
> +
> +       *stringp = next;
> +
> +       return orig;
>  }
>
>  /* A list of all modules we processed */
> --
> 2.26.2
>


-- 
Best Regards
Masahiro Yamada