diff options
authorMasahiro Yamada <yamada.masahiro@socionext.com>2017-11-08 01:31:46 +0900
committerMasahiro Yamada <yamada.masahiro@socionext.com>2017-11-18 11:38:58 +0900
commitf7adc3124da019878186f1ebe98a13a1af041afd (patch)
parent16f8259ca77d04f95e5ca90be1b1894ed45816c0 (diff)
kbuild: create built-in.o automatically if parent directory wants it
"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 descending. 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> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
2 files changed, 3 insertions, 3 deletions
diff --git a/Makefile b/Makefile
index 533fc1d0f283..b248be104ee0 100644
--- a/Makefile
+++ b/Makefile
@@ -1009,7 +1009,7 @@ $(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 f171225383cc..fc7f312bc0a7 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -76,7 +76,7 @@ lib-target := $(obj)/lib.a
obj-y += $(obj)/lib-ksyms.o
-ifneq ($(strip $(obj-y) $(obj-m) $(obj-) $(subdir-m) $(lib-target)),)
+ifneq ($(strip $(obj-y) $(need-builtin)),)
builtin-target := $(obj)/built-in.o
@@ -561,7 +561,7 @@ targets := $(filter-out $(PHONY), $(targets))
PHONY += $(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.
# ---------------------------------------------------------------------------