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Date:   Wed, 15 Jan 2020 13:19:02 -0800
From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
To:     Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Cc:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>,
        Doug Ledford <dledford@redhat.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <jakub.kicinski@netronome.com>,
        Jesper Dangaard Brouer <brouer@redhat.com>,
        John Fastabend <john.fastabend@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Shuah Khan <shuah@kernel.org>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-rdma@vger.kernel.org, linux-kselftest@vger.kernel.org,
        clang-built-linux@googlegroups.com
Subject: Re: [PATCH bpf-next v2 00/10] tools: Use consistent libbpf include
 paths everywhere
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On Wed, Jan 15, 2020 at 03:12:48PM +0100, Toke H?iland-J?rgensen wrote:
> The recent commit 6910d7d3867a ("selftests/bpf: Ensure bpf_helper_defs.h are
> taken from selftests dir") broke compilation against libbpf if it is installed
> on the system, and $INCLUDEDIR/bpf is not in the include path.
> 
> Since having the bpf/ subdir of $INCLUDEDIR in the include path has never been a
> requirement for building against libbpf before, this needs to be fixed. One
> option is to just revert the offending commit and figure out a different way to
> achieve what it aims for. However, this series takes a different approach:
> Changing all in-tree users of libbpf to consistently use a bpf/ prefix in
> #include directives for header files from libbpf.

I don't think such approach will work in all cases.
Consider the user installing libbpf headers into /home/somebody/include/bpf/,
passing that path to -I and trying to build bpf progs
that do #include "bpf_helpers.h"...
In the current shape of libbpf everything will compile fine,
but after patch 8 of this series the compiler will not find bpf/bpf_helper_defs.h.
So I think we have no choice, but to revert that part of Andrii's patch.
Note that doing #include "" for additional library headers is a common practice.
There was nothing wrong about #include "bpf_helper_defs.h" in bpf_helpers.h.