| Message ID | 1510072307-16819-2-git-send-email-yamada.masahiro@socionext.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Masahiro. Thanks for picking this up. > A key point is, the parent Makefile knows whether built-in.o is needed > or not. If a subdirectory needs to create built-in.o, its parent can > tell the fact when Kbuild descends into it. Good observation! > > diff --git a/Makefile b/Makefile > index 008a4e5..cc0b618 100644 > --- a/Makefile > +++ b/Makefile > @@ -1003,7 +1003,7 @@ $(sort $(vmlinux-deps)): $(vmlinux-dirs) ; > > PHONY += $(vmlinux-dirs) > $(vmlinux-dirs): prepare scripts > - $(Q)$(MAKE) $(build)=$@ > + $(Q)$(MAKE) $(build)=$@ need-builtin=1 The need-bultin may also be required for the shortcuts that allows one to use: make <dir>/ example: make net/ And maybe selftest, documentation shortcuts too? Other than that - looks good. Reviewed-by: Sam Ravnborg <sam@ravnborg.org> Sam -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Sam, Thanks for your review. 2017-11-09 14:35 GMT+09:00 Sam Ravnborg <sam@ravnborg.org>: > Hi Masahiro. > > Thanks for picking this up. > >> A key point is, the parent Makefile knows whether built-in.o is needed >> or not. If a subdirectory needs to create built-in.o, its parent can >> tell the fact when Kbuild descends into it. > Good observation! >> >> diff --git a/Makefile b/Makefile >> index 008a4e5..cc0b618 100644 >> --- a/Makefile >> +++ b/Makefile >> @@ -1003,7 +1003,7 @@ $(sort $(vmlinux-deps)): $(vmlinux-dirs) ; >> >> PHONY += $(vmlinux-dirs) >> $(vmlinux-dirs): prepare scripts >> - $(Q)$(MAKE) $(build)=$@ >> + $(Q)$(MAKE) $(build)=$@ need-builtin=1 > > The need-bultin may also be required for the shortcuts > that allows one to use: > > make <dir>/ > > example: > > make net/ I do not want to add need-builtin=1 for single targets. make scripts/ would create false scripts/built-in.o This is odd. I wrote the solution in the commit log: $(obj-y) should be still checked to support the single target "%/". If net/Makefile contains at least one obj-y, "make net/" will create built-in.o > And maybe selftest, documentation shortcuts too? > Other than that - looks good. > > Reviewed-by: Sam Ravnborg <sam@ravnborg.org> > > Sam > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Masahiro. On Thu, Nov 09, 2017 at 02:53:04PM +0900, Masahiro Yamada wrote: > Hi Sam, > > Thanks for your review. > > 2017-11-09 14:35 GMT+09:00 Sam Ravnborg <sam@ravnborg.org>: > > Hi Masahiro. > > > > Thanks for picking this up. > > > >> A key point is, the parent Makefile knows whether built-in.o is needed > >> or not. If a subdirectory needs to create built-in.o, its parent can > >> tell the fact when Kbuild descends into it. > > Good observation! > >> > >> diff --git a/Makefile b/Makefile > >> index 008a4e5..cc0b618 100644 > >> --- a/Makefile > >> +++ b/Makefile > >> @@ -1003,7 +1003,7 @@ $(sort $(vmlinux-deps)): $(vmlinux-dirs) ; > >> > >> PHONY += $(vmlinux-dirs) > >> $(vmlinux-dirs): prepare scripts > >> - $(Q)$(MAKE) $(build)=$@ > >> + $(Q)$(MAKE) $(build)=$@ need-builtin=1 > > > > The need-bultin may also be required for the shortcuts > > that allows one to use: > > > > make <dir>/ > > > > example: > > > > make net/ > > > I do not want to add need-builtin=1 for single targets. > > > make scripts/ > would create false scripts/built-in.o > This is odd. > > I wrote the solution in the commit log: > $(obj-y) should be still checked to support the single target "%/". I missed this bit in the commit log, but I almost commented on this in the patch itself. Good way to do it. Sam -- To unsubscribe from this list: send the line "unsubscribe linux-kbuild" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
2017-11-08 1:31 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>: > "obj-y += foo/" syntax requires Kbuild to visit the "foo" subdirectory > and link built-in.o from that directory. This means foo/Makefile is > responsible for creating built-in.o even if there is no object to > link (in this case, built-in.o is an empty archive). > > We have had several fixups like commit 4b024242e8a4 ("kbuild: Fix > linking error built-in.o no such file or directory"), then ended up > with a complex condition as follows: > > ifneq ($(strip $(obj-y) $(obj-m) $(obj-) $(subdir-m) $(lib-target)),) > builtin-target := $(obj)/built-in.o > endif > > We still have more cases not covered by the above, so we need to add > obj- := dummy.o > in several places just for creating empty built-in.o. > > A key point is, the parent Makefile knows whether built-in.o is needed > or not. If a subdirectory needs to create built-in.o, its parent can > tell the fact when Kbuild descends into it. > > If non-empty $(need-builtin) flag is passed from the parent, built-in.o > should be created. $(obj-y) should be still checked to support the > single target "%/". All of ugly tricks will go away. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > --- > Applied to linux-kbuild/kbuild.
diff --git a/Makefile b/Makefile index 008a4e5..cc0b618 100644 --- a/Makefile +++ b/Makefile @@ -1003,7 +1003,7 @@ $(sort $(vmlinux-deps)): $(vmlinux-dirs) ; PHONY += $(vmlinux-dirs) $(vmlinux-dirs): prepare scripts - $(Q)$(MAKE) $(build)=$@ + $(Q)$(MAKE) $(build)=$@ need-builtin=1 define filechk_kernel.release echo "$(KERNELVERSION)$$($(CONFIG_SHELL) $(srctree)/scripts/setlocalversion $(srctree))" diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 061d0c3..e1c6efd 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -84,7 +84,7 @@ lib-target := $(obj)/lib.a obj-y += $(obj)/lib-ksyms.o endif -ifneq ($(strip $(obj-y) $(obj-m) $(obj-) $(subdir-m) $(lib-target)),) +ifneq ($(strip $(obj-y) $(need-builtin)),) builtin-target := $(obj)/built-in.o endif @@ -569,7 +569,7 @@ targets += $(multi-used-y) $(multi-used-m) PHONY += $(subdir-ym) $(subdir-ym): - $(Q)$(MAKE) $(build)=$@ + $(Q)$(MAKE) $(build)=$@ need-builtin=$(if $(findstring $@,$(subdir-obj-y)),1) # Add FORCE to the prequisites of a target to force it to be always rebuilt. # ---------------------------------------------------------------------------
"obj-y += foo/" syntax requires Kbuild to visit the "foo" subdirectory and link built-in.o from that directory. This means foo/Makefile is responsible for creating built-in.o even if there is no object to link (in this case, built-in.o is an empty archive). We have had several fixups like commit 4b024242e8a4 ("kbuild: Fix linking error built-in.o no such file or directory"), then ended up with a complex condition as follows: ifneq ($(strip $(obj-y) $(obj-m) $(obj-) $(subdir-m) $(lib-target)),) builtin-target := $(obj)/built-in.o endif We still have more cases not covered by the above, so we need to add obj- := dummy.o in several places just for creating empty built-in.o. A key point is, the parent Makefile knows whether built-in.o is needed or not. If a subdirectory needs to create built-in.o, its parent can tell the fact when Kbuild descends into it. If non-empty $(need-builtin) flag is passed from the parent, built-in.o should be created. $(obj-y) should be still checked to support the single target "%/". All of ugly tricks will go away. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- Makefile | 2 +- scripts/Makefile.build | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-)