[PATCH 4.9 52/63] kbuild: clang: disable unused variable warnings only when constant

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sodagudi Prasad <psodagud@xxxxxxxxxxxxxx>

commit 0a5f41767444cc3b4fc5573921ab914b4f78baaa upstream.

Currently, GCC disables -Wunused-const-variable, but not
-Wunused-variable, so warns unused variables if they are
non-constant.

While, Clang does not warn unused variables at all regardless of
the const qualifier because -Wno-unused-const-variable is implied
by the stronger option -Wno-unused-variable.

Disable -Wunused-const-variable instead of -Wunused-variable so that
GCC and Clang work in the same way.

Signed-off-by: Prasad Sodagudi <psodagud@xxxxxxxxxxxxxx>
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 Makefile |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/Makefile
+++ b/Makefile
@@ -716,7 +716,6 @@ KBUILD_CFLAGS += $(stackp-flag)
 
 ifeq ($(cc-name),clang)
 KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
-KBUILD_CFLAGS += $(call cc-disable-warning, unused-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)
@@ -734,9 +733,9 @@ else
 # These warnings generated too much noise in a regular build.
 # Use make W=1 to enable them (see scripts/Makefile.extrawarn)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
-KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
 endif
 
+KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
 ifdef CONFIG_FRAME_POINTER
 KBUILD_CFLAGS	+= -fno-omit-frame-pointer -fno-optimize-sibling-calls
 else