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[2a01:cb08:8949:7e00:230:2090:c50a:60b9]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4900c16c744sm88940555e9.3.2026.05.18.11.49.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 May 2026 11:49:33 -0700 (PDT) Date: Mon, 18 May 2026 20:49:31 +0200 From: Paul Chaignon To: sashiko-reviews@lists.linux.dev Cc: bpf@vger.kernel.org Subject: Re: [PATCH bpf-next] selftests/bpf: Override EXTRA_LDFLAGS for static builds Message-ID: References: <714556da329c812988010ffe53173d9152570a78.1778669303.git.paul.chaignon@gmail.com> <20260514042304.EF3ECC2BCB7@smtp.kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20260514042304.EF3ECC2BCB7@smtp.kernel.org> On Thu, May 14, 2026 at 04:23:04AM +0000, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [Medium] The suggested workaround `EXTRA_LDFLAGS=-static` in README.rst breaks the bpftool build or silently disables LLVM support. > -- > > commit dcbd0d5d7a0eb4a9300ad0890d83b7e4cdfd3aeb > Author: Paul Chaignon > > selftests/bpf: Override EXTRA_LDFLAGS for static builds > > This commit updates the README.rst for BPF selftests to include > EXTRA_LDFLAGS=-static when recommending how to statically link, > in order to fix shared library loading errors with libLLVM.so > when running vmtest.sh. > > > diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst > > index 776fbe3cb8f9b..37164322a1023 100644 > > --- a/tools/testing/selftests/bpf/README.rst > > +++ b/tools/testing/selftests/bpf/README.rst > > @@ -77,7 +77,7 @@ In case of linker errors when running selftests, try using static linking: > > > > .. code-block:: console > > > > - $ LDLIBS=-static PKG_CONFIG='pkg-config --static' vmtest.sh > > + $ LDLIBS=-static EXTRA_LDFLAGS=-static PKG_CONFIG='pkg-config --static' vmtest.sh > > Can adding EXTRA_LDFLAGS=-static break the bpftool build or silently disable > LLVM support? > > In the bpftool Makefile, LLVM's --system-libs and -lstdc++ are only appended > to LIBS if llvm-config --shared-mode outputs 'static'. However, the > feature-llvm test in tools/build/feature/Makefile unconditionally includes > --system-libs and uses g++, which automatically includes -lstdc++. > > If a system has static LLVM libraries but llvm-config --shared-mode is set > to 'shared' (common on many distros), the feature-llvm test statically links > successfully, but bpftool's Makefile will attempt to build with LLVM support > using gcc -static while omitting --system-libs and -lstdc++. This can cause > the build to fail with undefined references. I'm not sure I'm following this, but I have static LLVM libraries with llvm-config --shared-mode set to "shared" and everything seems to build fine. > > Additionally, if static LLVM libraries are entirely absent, the feature test > fails, causing bpftool to silently build without LLVM support. > > -- > Sashiko AI review · https://sashiko.dev/#/patchset/714556da329c812988010ffe53173d9152570a78.1778669303.git.paul.chaignon@gmail.com?part=1