On Mon, Apr 12, 2021 at 7:29 AM Yonghong Song <yhs@xxxxxx> wrote:
>
> To build kernel with clang, people typically use
> make -j60 LLVM=1 LLVM_IAS=1
> LLVM_IAS=1 is not required for non-LTO build but
> is required for LTO build. In my environment,
> I am always having LLVM_IAS=1 regardless of
> whether LTO is enabled or not.
>
> After kernel is build with clang, the following command
> can be used to build selftests with clang:
> make -j60 -C tools/testing/selftests/bpf LLVM=1 LLVM_IAS=1
Thank you for the series Yonghong. When I test the above command with
your series applied, I observe:
/usr/bin/ld: cannot find -lcap
clang-13: error: linker command failed with exit code 1 (use -v to see
invocation)
I need to install libcap-dev, but this also seems to imply that BFD is
being used as the linker, not LLD. Perhaps if the compiler is being
used as the "driver" to also link executables, `-fuse-ld=lld` is
needed for the compiler flags.
Then there's:
tools/include/tools/libc_compat.h:11:21: error: static declaration of
'reallocarray' follows non-static declaration
static inline void *reallocarray(void *ptr, size_t nmemb, size_t size)
^
/usr/include/stdlib.h:559:14: note: previous declaration is here
extern void *reallocarray (void *__ptr, size_t __nmemb, size_t __size)
^
so perhaps the detection of
COMPAT_NEED_REALLOCARRAY/feature-reallocarray is incorrect?
>
> But currently, using the above command, some compilations
> still use gcc and there are also compilation errors and warnings.
> This patch set intends to fix these issues.
> Patch #1 and #2 fixed the issue so clang/clang++ is
> used instead of gcc/g++. Patch #3 fixed a compilation
> failure. Patch #4 and #5 fixed various compiler warnings.
>
> Changelog:
> v1 -> v2:
> . add -Wno-unused-command-line-argument and -Wno-format-security
> for clang only as (1). gcc does not exhibit those
> warnings, and (2). -Wno-unused-command-line-argument is
> only supported by clang. (Sedat)
>
> Yonghong Song (5):
> selftests: set CC to clang in lib.mk if LLVM is set
> tools: allow proper CC/CXX/... override with LLVM=1 in
> Makefile.include
> selftests/bpf: fix test_cpp compilation failure with clang
> selftests/bpf: silence clang compilation warnings
> bpftool: fix a clang compilation warning
>
> tools/bpf/bpftool/net.c | 2 +-
> tools/scripts/Makefile.include | 12 ++++++++++--
> tools/testing/selftests/bpf/Makefile | 7 ++++++-
> tools/testing/selftests/lib.mk | 4 ++++
> 4 files changed, 21 insertions(+), 4 deletions(-)
>
> --
> 2.30.2
>
--
Thanks,
~Nick Desaulniers
