kbuild: change *FLAGS_<basetarget>.o to take the path relative to $(obj)

Kbuild provides per-file compiler flag addition/removal:

  CFLAGS_<basetarget>.o
  CFLAGS_REMOVE_<basetarget>.o
  AFLAGS_<basetarget>.o
  AFLAGS_REMOVE_<basetarget>.o
  CPPFLAGS_<basetarget>.lds
  HOSTCFLAGS_<basetarget>.o
  HOSTCXXFLAGS_<basetarget>.o

The <basetarget> is the filename of the target with its directory and
suffix stripped.

This syntax comes into a trouble when two files with the same basename
appear in one Makefile, for example:

  obj-y += foo.o
  obj-y += dir/foo.o
  CFLAGS_foo.o := <some-flags>

Here, the <some-flags> applies to both foo.o and dir/foo.o

The real world problem is:

  scripts/kconfig/util.c
  scripts/kconfig/lxdialog/util.c

Both files are compiled into scripts/kconfig/mconf, but only the
latter should be given with the ncurses flags.

It is more sensible to use the relative path to the Makefile, like this:

  obj-y += foo.o
  CFLAGS_foo.o := <some-flags>
  obj-y += dir/foo.o
  CFLAGS_dir/foo.o := <other-flags>

At first, I attempted to replace $(basetarget) with $*. The $* variable
is replaced with the stem ('%') part in a pattern rule. This works with
most of cases, but does not for explicit rules.

For example, arch/ia64/lib/Makefile reuses rule_as_o_S in its own
explicit rules, so $* will be empty, resulting in ignoring the per-file
AFLAGS.

I introduced a new variable, target-stem, which can be used also from
explicit rules.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Marc Zyngier <maz@kernel.org>

3 files changed, 23 insertions, 20 deletions

diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index b402c619147d..4c51c95d40f4 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -80,9 +80,9 @@ host-cxxshobjs	:= $(addprefix $(obj)/,$(host-cxxshobjs))
 # Handle options to gcc. Support building with separate output directory
 
 _hostc_flags   = $(KBUILD_HOSTCFLAGS)   $(HOST_EXTRACFLAGS)   \
-                 $(HOSTCFLAGS_$(basetarget).o)
+                 $(HOSTCFLAGS_$(target-stem).o)
 _hostcxx_flags = $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
-                 $(HOSTCXXFLAGS_$(basetarget).o)
+                 $(HOSTCXXFLAGS_$(target-stem).o)
 
 # $(objtree)/$(obj) for including generated headers from checkin source files
 ifeq ($(KBUILD_EXTMOD),)
@@ -102,7 +102,7 @@ hostcxx_flags  = -Wp,-MD,$(depfile) $(_hostcxx_flags)
 # host-csingle -> Executable
 quiet_cmd_host-csingle  = HOSTCC  $@
       cmd_host-csingle  = $(HOSTCC) $(hostc_flags) $(KBUILD_HOSTLDFLAGS) -o $@ $< \
-                $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(@F))
+                $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
 $(host-csingle): $(obj)/%: $(src)/%.c FORCE
         $(call if_changed_dep,host-csingle)
 
@@ -110,8 +110,8 @@ $(host-csingle): $(obj)/%: $(src)/%.c FORCE
 # host-cmulti -> executable
 quiet_cmd_host-cmulti   = HOSTLD  $@
       cmd_host-cmulti   = $(HOSTCC) $(KBUILD_HOSTLDFLAGS) -o $@ \
-                          $(addprefix $(obj)/,$($(@F)-objs)) \
-                          $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(@F))
+                          $(addprefix $(obj)/, $($(target-stem)-objs)) \
+                          $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
 $(host-cmulti): FORCE
         $(call if_changed,host-cmulti)
 $(call multi_depend, $(host-cmulti), , -objs)
@@ -128,8 +128,8 @@ $(host-cobjs): $(obj)/%.o: $(src)/%.c FORCE
 quiet_cmd_host-cxxmulti = HOSTLD  $@
       cmd_host-cxxmulti = $(HOSTCXX) $(KBUILD_HOSTLDFLAGS) -o $@ \
                           $(foreach o,objs cxxobjs,\
-                          $(addprefix $(obj)/,$($(@F)-$(o)))) \
-                          $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(@F))
+                          $(addprefix $(obj)/, $($(target-stem)-$(o)))) \
+                          $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
 $(host-cxxmulti): FORCE
         $(call if_changed,host-cxxmulti)
 $(call multi_depend, $(host-cxxmulti), , -objs -cxxobjs)
@@ -161,8 +161,8 @@ $(host-cxxshobjs): $(obj)/%.o: $(src)/%.c FORCE
 # *.o -> .so shared library (host-cshlib)
 quiet_cmd_host-cshlib   = HOSTLLD -shared $@
       cmd_host-cshlib   = $(HOSTCC) $(KBUILD_HOSTLDFLAGS) -shared -o $@ \
-                          $(addprefix $(obj)/,$($(@F:.so=-objs))) \
-                          $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(@F))
+                          $(addprefix $(obj)/, $($(target-stem)-objs)) \
+                          $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem).so)
 $(host-cshlib): FORCE
         $(call if_changed,host-cshlib)
 $(call multi_depend, $(host-cshlib), .so, -objs)
@@ -171,8 +171,8 @@ $(call multi_depend, $(host-cshlib), .so, -objs)
 # *.o -> .so shared library (host-cxxshlib)
 quiet_cmd_host-cxxshlib = HOSTLLD -shared $@
       cmd_host-cxxshlib = $(HOSTCXX) $(KBUILD_HOSTLDFLAGS) -shared -o $@ \
-                          $(addprefix $(obj)/,$($(@F:.so=-objs))) \
-                          $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(@F))
+                          $(addprefix $(obj)/, $($(target-stem)-objs)) \
+                          $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem).so)
 $(host-cxxshlib): FORCE
         $(call if_changed,host-cxxshlib)
 $(call multi_depend, $(host-cxxshlib), .so, -objs)
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 7ab17712ab24..380a7d11a573 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -101,6 +101,9 @@ modname-multi = $(subst $(space),:,$(sort $(foreach m,$(multi-used),\
 
 modname = $(if $(modname-multi),$(modname-multi),$(basetarget))
 
+# target with $(obj)/ and its suffix stripped
+target-stem = $(basename $(patsubst $(obj)/%,%,$@))
+
 # These flags are needed for modversions and compiling, so we define them here
 # $(modname_flags) defines KBUILD_MODNAME as the name of the module it will
 # end up in (or would, if it gets compiled in)
@@ -109,12 +112,12 @@ basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
 modname_flags  = -DKBUILD_MODNAME=$(call name-fix,$(modname))
 
 orig_c_flags   = $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) \
-                 $(ccflags-y) $(CFLAGS_$(basetarget).o)
-_c_flags       = $(filter-out $(CFLAGS_REMOVE_$(basetarget).o), $(orig_c_flags))
+                 $(ccflags-y) $(CFLAGS_$(target-stem).o)
+_c_flags       = $(filter-out $(CFLAGS_REMOVE_$(target-stem).o), $(orig_c_flags))
 orig_a_flags   = $(KBUILD_CPPFLAGS) $(KBUILD_AFLAGS) \
-                 $(asflags-y) $(AFLAGS_$(basetarget).o)
-_a_flags       = $(filter-out $(AFLAGS_REMOVE_$(basetarget).o), $(orig_a_flags))
-_cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(@F))
+                 $(asflags-y) $(AFLAGS_$(target-stem).o)
+_a_flags       = $(filter-out $(AFLAGS_REMOVE_$(target-stem).o), $(orig_a_flags))
+_cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(target-stem).lds)
 
 #
 # Enable gcov profiling flags for a file, directory or for all files depending
diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index bed7a5a2fbe9..ef2f2336c469 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -166,15 +166,15 @@ $(obj)/nconf.o $(obj)/nconf.gui.o: $(obj)/nconf-cfg
 
 # mconf: Used for the menuconfig target based on lxdialog
 hostprogs-y     += mconf
-lxdialog        := checklist.o inputbox.o menubox.o textbox.o util.o yesno.o
-mconf-objs      := mconf.o $(addprefix lxdialog/, $(lxdialog)) $(common-objs)
+lxdialog        := $(addprefix lxdialog/, \
+                     checklist.o inputbox.o menubox.o textbox.o util.o yesno.o)
+mconf-objs      := mconf.o $(lxdialog) $(common-objs)
 
 HOSTLDLIBS_mconf = $(shell . $(obj)/mconf-cfg && echo $$libs)
 $(foreach f, mconf.o $(lxdialog), \
   $(eval HOSTCFLAGS_$f = $$(shell . $(obj)/mconf-cfg && echo $$$$cflags)))
 
-$(obj)/mconf.o: $(obj)/mconf-cfg
-$(addprefix $(obj)/lxdialog/, $(lxdialog)): $(obj)/mconf-cfg
+$(addprefix $(obj)/, mconf.o $(lxdialog)): $(obj)/mconf-cfg
 
 # qconf: Used for the xconfig target based on Qt
 hostprogs-y     += qconf