Commit 30a77297 authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

kbuild: use -MMD instead of -MD to exclude system headers from dependency 



This omits system headers from the generated header dependency.

System headers are not updated unless you upgrade the compiler. Nor do
they contain CONFIG options, so fixdep does not need to parse them.

Having said that, the effect of this optimization will be quite small
because the kernel code generally does not include system headers
except <stdarg.h>. Host programs include a lot of system headers,
but there are not so many in the kernel tree.

At first, keeping system headers in .*.cmd files might be useful to
detect the compiler update, but there is no guarantee that <stdarg.h>
is included from every file. So, I implemented a more reliable way in
the previous commit.

Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
parent 8b59cd81

scripts/Kbuild.include

+1 −1
Original line number Diff line number Diff line
@@ -16,7 +16,7 @@ pound := \# 
dot-target = $(dir $@).$(notdir $@)



###

# The temporary file to save gcc -MD generated dependencies must not

# The temporary file to save gcc -MMD generated dependencies must not

# contain a comma

depfile = $(subst $(comma),_,$(dot-target).d)

scripts/Makefile.host

+2 −2
Original line number Diff line number Diff line
@@ -88,8 +88,8 @@ _hostcxx_flags += -I $(objtree)/$(obj) 
endif

endif



hostc_flags    = -Wp,-MD,$(depfile) $(_hostc_flags)

hostcxx_flags  = -Wp,-MD,$(depfile) $(_hostcxx_flags)

hostc_flags    = -Wp,-MMD,$(depfile) $(_hostc_flags)

hostcxx_flags  = -Wp,-MMD,$(depfile) $(_hostcxx_flags)



#####

# Compile programs on the host

scripts/Makefile.lib

+4 −4
Original line number Diff line number Diff line
@@ -171,22 +171,22 @@ modkern_aflags = $(if $(part-of-module), \ 
			$(KBUILD_AFLAGS_MODULE) $(AFLAGS_MODULE),	\

			$(KBUILD_AFLAGS_KERNEL) $(AFLAGS_KERNEL))



c_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \

c_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \

		 -include $(srctree)/include/linux/compiler_types.h       \

		 $(_c_flags) $(modkern_cflags)                           \

		 $(basename_flags) $(modname_flags)



a_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \

a_flags        = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \

		 $(_a_flags) $(modkern_aflags)



cpp_flags      = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \

cpp_flags      = -Wp,-MMD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \

		 $(_cpp_flags)



ld_flags       = $(KBUILD_LDFLAGS) $(ldflags-y) $(LDFLAGS_$(@F))



DTC_INCLUDE    := $(srctree)/scripts/dtc/include-prefixes



dtc_cpp_flags  = -Wp,-MD,$(depfile).pre.tmp -nostdinc                    \

dtc_cpp_flags  = -Wp,-MMD,$(depfile).pre.tmp -nostdinc                    \

		 $(addprefix -I,$(DTC_INCLUDE))                          \

		 -undef -D__DTS__

usr/include/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -8,7 +8,7 @@ 
# We cannot go as far as adding -Wpedantic since it emits too many warnings.

UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration



override c_flags = $(UAPI_CFLAGS) -Wp,-MD,$(depfile) -I$(objtree)/usr/include

override c_flags = $(UAPI_CFLAGS) -Wp,-MMD,$(depfile) -I$(objtree)/usr/include



# The following are excluded for now because they fail to build.

#

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