linux-kernel - Re: [PATCH v2 3/3] libsubcmd: Silence compiler warning

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Message-ID: <CAEf4BzbOMhw2yRTbN-n65TsDu+Zi8c-A6uVLN4SP7_Xpruttvg@mail.gmail.com>
Date: Tue, 22 Oct 2024 16:18:15 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Eder Zulian <ezulian@...hat.com>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, ast@...nel.org, 
	daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev, 
	eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, acme@...hat.com, vmalik@...hat.com, 
	williams@...hat.com
Subject: Re: [PATCH v2 3/3] libsubcmd: Silence compiler warning

On Tue, Oct 22, 2024 at 10:24 AM Eder Zulian <ezulian@...hat.com> wrote:
>
> Initialize the pointer 'o' in options__order to NULL to prevent a
> compiler warning/error which is observed when compiling with the '-Og'
> option, but is not emitted by the compiler with the current default
> compilation options.
>
> For example, when compiling libsubcmd with
>
>  $ make "EXTRA_CFLAGS=-Og" -C tools/lib/subcmd/ clean all
>
> Clang version 17.0.6 and GCC 13.3.1 fail to compile parse-options.c due
> to following error:
>
>   parse-options.c: In function ‘options__order’:
>   parse-options.c:832:9: error: ‘o’ may be used uninitialized [-Werror=maybe-uninitialized]
>     832 |         memcpy(&ordered[nr_opts], o, sizeof(*o));
>         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   parse-options.c:810:30: note: ‘o’ was declared here
>     810 |         const struct option *o, *p = opts;
>         |                              ^
>   cc1: all warnings being treated as errors
>
> Signed-off-by: Eder Zulian <ezulian@...hat.com>
> ---
>  tools/lib/subcmd/parse-options.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>

First two patches look good, we can take them through bpf-next. What
do we do with this one? Arnaldo, would you like us to take it through
bpf-next as well (if yes, please give your ack), or you'd like to take
it through your tree?

> diff --git a/tools/lib/subcmd/parse-options.c b/tools/lib/subcmd/parse-options.c
> index eb896d30545b..555d617c1f50 100644
> --- a/tools/lib/subcmd/parse-options.c
> +++ b/tools/lib/subcmd/parse-options.c
> @@ -807,7 +807,7 @@ static int option__cmp(const void *va, const void *vb)
>  static struct option *options__order(const struct option *opts)
>  {
>         int nr_opts = 0, nr_group = 0, nr_parent = 0, len;
> -       const struct option *o, *p = opts;
> +       const struct option *o = NULL, *p = opts;
>         struct option *opt, *ordered = NULL, *group;
>
>         /* flatten the options that have parents */
> --
> 2.46.2
>