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. Theoretically, fixdep does not need to cater to host programs because they should not contain CONFIG options in the first place. fixdep actually does just because Kbuild reuses if_changed_dep for host programs. 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: Masahiro Yamada <masahiroy@xxxxxxxxxx> --- Changes in v2: None scripts/Kbuild.include | 2 +- scripts/Makefile.host | 4 ++-- scripts/Makefile.lib | 8 ++++---- 3 files changed, 7 insertions(+), 7 deletions(-) diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 6cabf20ce66a..0c3dc983439b 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -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) diff --git a/scripts/Makefile.host b/scripts/Makefile.host index 2045855d0b75..c8a4a033dc3e 100644 --- a/scripts/Makefile.host +++ b/scripts/Makefile.host @@ -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 diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 97547108ee7f..a94c1e741df9 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -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__ -- 2.25.1
