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authorBehan Webster <behanw@converseincode.com>2013-09-03 22:27:23 -0400
committerBehan Webster <behanw@converseincode.com>2014-04-09 13:44:34 -0700
commit61163efae02040f66a95c8ed17f4407951ba58fa (patch)
treef4153900fa31a58ff6efeafc9db53b45cb71cfb4
parentMerge branch 'i2c/for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux (diff)
downloadlinux-dev-61163efae02040f66a95c8ed17f4407951ba58fa.tar.xz
linux-dev-61163efae02040f66a95c8ed17f4407951ba58fa.zip
kbuild: LLVMLinux: Add Kbuild support for building kernel with Clang
Add support to toplevel Makefile for compiling with clang, both for HOSTCC and CC. Use cc-option to prevent gcc option from breaking clang, and from clang options from breaking gcc. Clang 3.4 semantics are the same as gcc semantics for unsupported flags. For unsupported warnings clang 3.4 returns true but shows a warning and gcc shows a warning and returns false. Signed-off-by: Behan Webster <behanw@converseincode.com> Signed-off-by: Jan-Simon Möller <dl9pf@gmx.de> Signed-off-by: Mark Charlebois <charlebm@gmail.com> Cc: PaX Team <pageexec@freemail.hu>
-rw-r--r--Makefile30
1 files changed, 29 insertions, 1 deletions
diff --git a/Makefile b/Makefile
index cf3e07516a04..10812e495e8d 100644
--- a/Makefile
+++ b/Makefile
@@ -248,6 +248,11 @@ HOSTCXX = g++
HOSTCFLAGS = -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 -fomit-frame-pointer
HOSTCXXFLAGS = -O2
+ifeq ($(shell $(HOSTCC) -v 2>&1 | grep -c "clang version"), 1)
+HOSTCFLAGS += -Wno-unused-value -Wno-unused-parameter \
+ -Wno-missing-field-initializers -fno-delete-null-pointer-checks
+endif
+
# Decide whether to build built-in, modular, or both.
# Normally, just do built-in.
@@ -324,6 +329,14 @@ endif
export quiet Q KBUILD_VERBOSE
+ifneq ($(CC),)
+ifeq ($(shell $(CC) -v 2>&1 | grep -c "clang version"), 1)
+COMPILER := clang
+else
+COMPILER := gcc
+endif
+export COMPILER
+endif
# Look for make include files relative to root of kernel src
MAKEFLAGS += --include-dir=$(srctree)
@@ -383,7 +396,7 @@ KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
-fno-strict-aliasing -fno-common \
-Werror-implicit-function-declaration \
-Wno-format-security \
- -fno-delete-null-pointer-checks
+ $(call cc-option,-fno-delete-null-pointer-checks,)
KBUILD_AFLAGS_KERNEL :=
KBUILD_CFLAGS_KERNEL :=
KBUILD_AFLAGS := -D__ASSEMBLY__
@@ -623,9 +636,24 @@ endif
endif
KBUILD_CFLAGS += $(stackp-flag)
+ifeq ($(COMPILER),clang)
+KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
+KBUILD_CPPFLAGS += $(call cc-option,-Wno-unknown-warning-option,)
+KBUILD_CFLAGS += $(call cc-disable-warning, unused-variable)
+KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
+KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
+# Quiet clang warning: comparison of unsigned expression < 0 is always false
+KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare)
+# CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
+# source of a reference will be _MergedGlobals and not on of the whitelisted names.
+# See modpost pattern 2
+KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,)
+else
+
# This warning generated too much noise in a regular build.
# Use make W=1 to enable this warning (see scripts/Makefile.build)
KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
+endif
ifdef CONFIG_FRAME_POINTER
KBUILD_CFLAGS += -fno-omit-frame-pointer -fno-optimize-sibling-calls