[PATCH bpf-next v2 0/5] bpf: tools: support build selftests/bpf with clang

[Yonghong Song <yhs@fb.com>]

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

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