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>

1 files changed, 4 insertions, 4 deletions

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