[PATCH bpf-next v1 2/7] selftests/bpf: don't pass clang-only warning flags to GCC
From: Vineet Gupta
Date: Tue Oct 27 2026 - 20:04:51 EST
The clang only togges are passed to every BPF object build, including
for BPF_GCC build.
GCC accepts an unknown -Wno-foo silently until some other diagnostic fires,
and then appends a note to it, so every warning in a bpf_gcc build comes with
two lines of noise:
cc1: note: unrecognized command-line option '-Wno-initializer-overrides' may have been intended to silence earlier diagnostics
cc1: note: unrecognized command-line option '-Wno-microsoft-anon-tag' may have been intended to silence earlier diagnostics
Collect them in CLANG_BPF_CFLAGS and hand them only to the clang
flavors, through the per-flavor BPF_CC_FLAGS that Makefile.skel appends
after BPF_CFLAGS.
Only these two are clang-only; -Wno-compare-distinct-pointer-types and
-fms-extensions are understood by GCC 14 and later and stay in
BPF_CFLAGS.
Signed-off-by: Vineet Gupta <vineet.gupta@xxxxxxxxx>
---
tools/testing/selftests/bpf/Makefile | 8 ++++----
tools/testing/selftests/bpf/Makefile.buildvars | 6 ++++--
2 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 1e4af62e8312..b5303c28973e 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -376,7 +376,7 @@ CLANG_TARGET_ARCH = --target=$(notdir $(CROSS_COMPILE:%-=%))
endif
CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG),$(CLANG_TARGET_ARCH))
-CLANG_CFLAGS = $(CLANG_SYS_INCLUDES)
+CLANG_CFLAGS = $(CLANG_SYS_INCLUDES) $(CLANG_BPF_CFLAGS)
# genkey writes both outputs. Pattern rules group them even on make
# versions before 4.3, preventing concurrent genkey invocations.
@@ -521,7 +521,7 @@ BINARY := test_progs
BPF_CC := $(CLANG)
BPF_CC_MSG := CLNG-BPF
BPF_SYS_INCLUDES := $(CLANG_SYS_INCLUDES)
-BPF_CC_FLAGS := -O2 $(BPF_TARGET_ENDIAN) -mcpu=v3
+BPF_CC_FLAGS := -O2 $(BPF_TARGET_ENDIAN) -mcpu=v3 $(CLANG_BPF_CFLAGS)
BPF_DEFINES := -DENABLE_ATOMICS_TESTS
include Makefile.skel
@@ -537,12 +537,12 @@ $(OUTPUT)/test_progs: $(RUNNER_PREREQS) $(BPF_OBJS) $(ALL_SKELS) FORCE
$(OUTPUT)/test_progs-no_alu32: $(RUNNER_PREREQS) FORCE
+$(Q)$(RUNNER_MAKE) RUNNER=test_progs FLAVOR=no_alu32 TESTS_DIR=prog_tests \
- $(CLANG_RUNNER_ARGS) BPF_CC_FLAGS='-O2 $(BPF_TARGET_ENDIAN) -mcpu=v2'
+ $(CLANG_RUNNER_ARGS) BPF_CC_FLAGS='-O2 $(BPF_TARGET_ENDIAN) -mcpu=v2 $(CLANG_BPF_CFLAGS)'
ifneq ($(CLANG_CPUV4),)
$(OUTPUT)/test_progs-cpuv4: $(RUNNER_PREREQS) FORCE
+$(Q)$(RUNNER_MAKE) RUNNER=test_progs FLAVOR=cpuv4 TESTS_DIR=prog_tests \
- $(CLANG_RUNNER_ARGS) BPF_CC_FLAGS='-O2 $(BPF_TARGET_ENDIAN) -mcpu=v4' \
+ $(CLANG_RUNNER_ARGS) BPF_CC_FLAGS='-O2 $(BPF_TARGET_ENDIAN) -mcpu=v4 $(CLANG_BPF_CFLAGS)' \
BPF_DEFINES=-DENABLE_ATOMICS_TESTS
endif
diff --git a/tools/testing/selftests/bpf/Makefile.buildvars b/tools/testing/selftests/bpf/Makefile.buildvars
index ff3476bc40a4..8ae2792c0c1e 100644
--- a/tools/testing/selftests/bpf/Makefile.buildvars
+++ b/tools/testing/selftests/bpf/Makefile.buildvars
@@ -157,13 +157,15 @@ BPF_CFLAGS = -g -Wall -Werror -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN) \
-I$(abspath $(OUTPUT)/../usr/include) \
-std=gnu11 \
-fno-strict-aliasing \
- -Wno-microsoft-anon-tag \
-fms-extensions \
-Wno-compare-distinct-pointer-types \
- -Wno-initializer-overrides \
#
# TODO: enable me -Wsign-compare
+# Warning flags that only clang has. GCC accepts an unknown -Wno-foo
+# silently and then notes it on the next diagnostic it emits.
+CLANG_BPF_CFLAGS := -Wno-microsoft-anon-tag -Wno-initializer-overrides
+
VERIFY_SIG_SETUP := $(CURDIR)/verify_sig_setup.sh
VERIFICATION_CERT := $(BUILD_DIR)/signing_key.der
PRIVATE_KEY := $(BUILD_DIR)/signing_key.pem
--
2.53.0-Meta