On 4/13/21 3:17 PM, Nick Desaulniers wrote:
On Tue, Apr 13, 2021 at 3:08 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
On Tue, Apr 13, 2021 at 8:34 AM Yonghong Song <yhs@xxxxxx> wrote:
With clang compiler:
make -j60 LLVM=1 LLVM_IAS=1 <=== compile kernel
make -j60 -C tools/testing/selftests/bpf LLVM=1 LLVM_IAS=1
Some linker flags are not used/effective for some binaries and
we have warnings like:
warning: -lelf: 'linker' input unused [-Wunused-command-line-argument]
We also have warnings like:
.../selftests/bpf/prog_tests/ns_current_pid_tgid.c:74:57: note: treat the string as an argument to avoid this
if (CHECK(waitpid(cpid, &wstatus, 0) == -1, "waitpid", strerror(errno)))
^
"%s",
.../selftests/bpf/test_progs.h:129:35: note: expanded from macro 'CHECK'
_CHECK(condition, tag, duration, format)
^
.../selftests/bpf/test_progs.h:108:21: note: expanded from macro '_CHECK'
fprintf(stdout, ##format); \
^
The first warning can be silenced with clang option -Wno-unused-command-line-argument.
For the second warning, source codes are modified as suggested by the compiler
to silence the warning. Since gcc does not support the option
-Wno-unused-command-line-argument and the warning only happens with clang
compiler, the option -Wno-unused-command-line-argument is enabled only when
clang compiler is used.
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
LGTM, please see the question below.
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
tools/testing/selftests/bpf/Makefile | 5 +++++
tools/testing/selftests/bpf/prog_tests/fexit_sleep.c | 4 ++--
tools/testing/selftests/bpf/prog_tests/ns_current_pid_tgid.c | 4 ++--
3 files changed, 9 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index dcc2dc1f2a86..c45ae13b88a0 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -28,6 +28,11 @@ CFLAGS += -g -Og -rdynamic -Wall $(GENFLAGS) $(SAN_CFLAGS) \
-Dbpf_load_program=bpf_test_load_program
LDLIBS += -lcap -lelf -lz -lrt -lpthread
+# Silence some warnings when compiled with clang
+ifneq ($(LLVM),)
This won't handle the case where someone does `make CC=clang`, right?
Do we care at all?
Right; it would be better to check CC=clang and have LLVM=1 enable
CC=clang from a higher level Makefile (since tools/build/Makefile
seems to override the top level $CC). See the top level Makefile
L448-456. Then it should work for CC=clang or LLVM=1.
I would consider LLVM=1 is recommended and should be supported
first. Support for CC=clang CXX=clang++ etc. can be done later
if people find cases where LLVM=1 does not fit their need.
+CFLAGS += -Wno-unused-command-line-argument
+endif
+
[...]
