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From:   Andrii Nakryiko <andrii.nakryiko@gmail.com>
Date:   Thu, 19 Sep 2019 13:02:40 -0700
Message-ID: <CAEf4BzbCjCYr5NMPctDkUggwpehnqZPVBSqZOsd9MvSq6WmnZQ@mail.gmail.com>
Subject: Re: [PATCH bpf] libbpf: fix version identification on busybox
To:     Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin Lau <kafai@fb.com>, Andrii Nakryiko <andriin@fb.com>,
        Yonghong Song <yhs@fb.com>,
        Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
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On Thu, Sep 19, 2019 at 11:22 AM Ivan Khoronzhuk
<ivan.khoronzhuk@linaro.org> wrote:
>
> It's very often for embedded to have stripped version of sort in
> busybox, when no -V option present. It breaks build natively on target
> board causing recursive loop.
>
> BusyBox v1.24.1 (2019-04-06 04:09:16 UTC) multi-call binary. \
> Usage: sort [-nrugMcszbdfimSTokt] [-o FILE] [-k \
> start[.offset][opts][,end[.offset][opts]] [-t CHAR] [FILE]...
>
> Lets modify command a little to avoid -V option.
>
> Fixes: dadb81d0afe732 ("libbpf: make libbpf.map source of truth for libbpf version")
>
> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
> ---
>
> Based on bpf/master
>
>  tools/lib/bpf/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
> index c6f94cffe06e..a12490ad6215 100644
> --- a/tools/lib/bpf/Makefile
> +++ b/tools/lib/bpf/Makefile
> @@ -3,7 +3,7 @@
>
>  LIBBPF_VERSION := $(shell \
>         grep -oE '^LIBBPF_([0-9.]+)' libbpf.map | \
> -       sort -rV | head -n1 | cut -d'_' -f2)
> +       cut -d'_' -f2 | sort -r | head -n1)

You can't just sort alphabetically, because:

1.2
1.11

should be in that order. See discussion on mailing thread for original commit.

>  LIBBPF_MAJOR_VERSION := $(firstword $(subst ., ,$(LIBBPF_VERSION)))
>
>  MAKEFLAGS += --no-print-directory
> --
> 2.17.1
>