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, 8 insertions, 5 deletions

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