[Changes from V1: - Build rule simplified, as there is no need to use $(if ...)] Certain BPF selftests contain code that, albeit being legal C, trigger warnings in GCC that cannot be disabled. This is the case for example for the tests progs/btf_dump_test_case_bitfields.c progs/btf_dump_test_case_namespacing.c progs/btf_dump_test_case_packing.c progs/btf_dump_test_case_padding.c progs/btf_dump_test_case_syntax.c which contain struct type declarations inside function parameter lists. This is problematic, because: - The BPF selftests are built with -Werror. - The Clang and GCC compilers sometimes differ when it comes to handle warnings. in the handling of warnings. One compiler may emit warnings for code that the other compiles compiles silently, and one compiler may offer the possibility to disable certain warnings, while the other doesn't. In order to overcome this problem, this patch modifies the tools/testing/selftests/bpf/Makefile in order to: 1. Enable the possibility of specifing per-source-file extra CFLAGS. This is done by defining a make variable like: <source-filename>-CFLAGS := <whateverflags> And then modifying the proper Make rule in order to use these flags when compiling <source-filename>. 2. Use the mechanism above to add -Wno-error to CFLAGS for the following selftests: progs/btf_dump_test_case_bitfields.c progs/btf_dump_test_case_namespacing.c progs/btf_dump_test_case_packing.c progs/btf_dump_test_case_padding.c progs/btf_dump_test_case_syntax.c Note the corresponding -CFLAGS variables for these files are defined only if the selftests are being built with GCC. Note that, while compiler pragmas can generally be used to disable particular warnings per file, this 1) is only possible for warning that actually can be disabled in the command line, i.e. that have -Wno-FOO options, and 2) doesn't apply to -Wno-error. Tested in bpf-next master branch. No regressions. Signed-off-by: Jose E. Marchesi <jose.marchesi@xxxxxxxxxx> Cc: Yonghong Song <yhs@xxxxxxxx> Cc: Eduard Zingerman <eddyz87@xxxxxxxxx> Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> Cc: david.faust@xxxxxxxxxx Cc: cupertino.miranda@xxxxxxxxxx --- tools/testing/selftests/bpf/Makefile | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile index fd15017ed3b1..1a3654bcb5dd 100644 --- a/tools/testing/selftests/bpf/Makefile +++ b/tools/testing/selftests/bpf/Makefile @@ -64,6 +64,15 @@ TEST_INST_SUBDIRS := no_alu32 ifneq ($(BPF_GCC),) TEST_GEN_PROGS += test_progs-bpf_gcc TEST_INST_SUBDIRS += bpf_gcc + +# The following tests contain C code that, although technically legal, +# triggers GCC warnings that cannot be disabled: declaration of +# anonymous struct types in function parameter lists. +progs/btf_dump_test_case_bitfields.c-CFLAGS := -Wno-error +progs/btf_dump_test_case_namespacing.c-CFLAGS := -Wno-error +progs/btf_dump_test_case_packing.c-CFLAGS := -Wno-error +progs/btf_dump_test_case_padding.c-CFLAGS := -Wno-error +progs/btf_dump_test_case_syntax.c-CFLAGS := -Wno-error endif ifneq ($(CLANG_CPUV4),) @@ -504,7 +513,8 @@ $(TRUNNER_BPF_OBJS): $(TRUNNER_OUTPUT)/%.bpf.o: \ $(wildcard $(BPFDIR)/*.bpf.h) \ | $(TRUNNER_OUTPUT) $$(BPFOBJ) $$(call $(TRUNNER_BPF_BUILD_RULE),$$<,$$@, \ - $(TRUNNER_BPF_CFLAGS)) + $(TRUNNER_BPF_CFLAGS) \ + $$($$<-CFLAGS)) $(TRUNNER_BPF_SKELS): %.skel.h: %.bpf.o $(BPFTOOL) | $(TRUNNER_OUTPUT) $$(call msg,GEN-SKEL,$(TRUNNER_BINARY),$$@) -- 2.30.2
