On 2017-12-06 22:26, Greg Kroah-Hartman wrote:
On Wed, Dec 06, 2017 at 01:24:51PM -0800, Sodagudi Prasad wrote:
Hi All,
When kernel compiled with clang, following line is disabling the
unused-variable warning. This is not the case with gcc.
KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable)
Are there any specific reasons for disabling unused-variable with
clang?
Try it and see why it is disabled :)
Hi Greg,
When I have enabled -Wunused-variable warnings with clang, observed both
-Wunused-variable and -Wunused-const-variable as expected.
It looks that, -Wunused-const-variable warnings are disabled explicitly
with GCC as well.
commit - c9c6837d39311b0c - "kbuild: move -Wunused-const-variable to
W=1 warning level"
I could see following warnings along with couple of -Wunused-variables
warnings with downstream code.
arch/arm64/crypto/sha1-ce-glue.c:118:1: warning: unused variable
'cpu_feature_match_SHA1' [-Wunused-const-variable]
include/linux/cpufeature.h:48:33: note: expanded from macro
'module_cpu_feature_match'
arch/arm64/crypto/sha2-ce-glue.c:148:1: warning: unused variable
'cpu_feature_match_SHA2' [-Wunused-const-variable]
arch/arm64/crypto/ghash-ce-glue.c:597:33: warning: unused variable
'ghash_cpu_feature' [-Wunused-const-variable]
arch/arm64/crypto/aes-ce-cipher.c:280:1: warning: unused variable
'cpu_feature_match_AES' [-Wunused-const-variable]
arch/arm64/crypto/aes-glue.c:674:1: warning: unused variable
'cpu_feature_match_AES' [-Wunused-const-variable]
kernel/trace/ftrace.c:1092:27: warning: unused variable
'ftrace_swapper_pid' [-Wunused-const-variable]
drivers/usb/host/ehci-platform.c:406:36: warning: unused variable
'ehci_acpi_match' [-Wunused-const-variable]
drivers/usb/host/xhci-plat.c:416:36: warning: unused variable
'usb_xhci_acpi_match' [-Wunused-const-variable]
So I have made following change and I will share patch for the same.
diff --git a/Makefile b/Makefile
index 4e6da2f..8a6c14e 100644
--- a/Makefile
+++ b/Makefile
@@ -711,7 +711,7 @@ endif
KBUILD_CFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC) -meabi gnu
KBUILD_AFLAGS += $(CLANG_TARGET) $(CLANG_GCC_TC)
KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
-KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable)
+KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
Please let me know if you have any concerns with this approach to
identify all unused local variables.
-Thanks, Prasad
--
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
Linux Foundation Collaborative Project
--
To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
