[Qemu-devel] [RFC PATCH v2 1/6] make.rule: fix $(obj) to a real relative path

[Fam Zheng <famz@redhat.com>]

Makefile.target includes rule.mak and unnested common-obj-y, then prefix
them with '../', this will ignore object specific QEMU_CFLAGS in subdir
Makefile.objs:

    $(obj)/curl.o: QEMU_CFLAGS += $(CURL_CFLAGS)

Because $(obj) here is './block', instead of '../block'. This doesn't
hurt compiling because we basically build all .o from top Makefile,
before entering Makefile.target, but it will affact arriving per-object
libs support.

The starting point of $(obj) is fixed in $(obj-base) before including
./Makefile.objs, to get consistency with nested Makefile rules in target
rule and variable definition.

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 Makefile.target | 3 ++-
 rules.mak       | 7 ++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/Makefile.target b/Makefile.target
index 9a49852..0ab60bd 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -144,12 +144,13 @@ endif # CONFIG_SOFTMMU
 %/translate.o: QEMU_CFLAGS += $(TRANSLATE_OPT_CFLAGS)
 
 nested-vars += obj-y
+obj-base := ..
 
 # This resolves all nested paths, so it must come last
 include $(SRC_PATH)/Makefile.objs
 
 all-obj-y = $(obj-y)
-all-obj-y += $(addprefix ../, $(common-obj-y))
+all-obj-y += $(addprefix $(obj)/, $(common-obj-y))
 
 ifndef CONFIG_HAIKU
 LIBS+=-lm
diff --git a/rules.mak b/rules.mak
index 4499745..eef1b71 100644
--- a/rules.mak
+++ b/rules.mak
@@ -103,7 +103,7 @@ clean: clean-timestamp
 
 # magic to descend into other directories
 
-obj := .
+obj = $(obj-base)
 old-nested-dirs :=
 
 define push-var
@@ -119,9 +119,10 @@ endef
 
 define unnest-dir
 $(foreach var,$(nested-vars),$(call push-var,$(var),$1/))
-$(eval obj := $(obj)/$1)
+$(eval old-obj := $(obj))
+$(eval obj := $(if $(obj),$(obj)/$1,$1))
 $(eval include $(SRC_PATH)/$1/Makefile.objs)
-$(eval obj := $(patsubst %/$1,%,$(obj)))
+$(eval obj := $(old-obj))
 $(foreach var,$(nested-vars),$(call pop-var,$(var),$1/))
 endef
 
-- 
1.8.3.1