[PATCH 4/5] kbuild: hdrtest: place header test files in .hdrtest subdirectories

[Jani Nikula <jani.nikula@intel.com>]

The header tests track whether headers have been checked using empty
*.hdrtest files in the build tree. This pollutes the build directories,
as the files live in the same "name space" as the real output files,
messing with TAB completion among other things.

Hide the disgusting turds by placing them in .hdrtest subdirectories.

Note that it would be somewhat nicer to have the basename of the
.hdrtest files be dot-prefixed instead of using subdirectories. However,
it's challenging to come up with a pattern rule for that, as we can list
headers to test in the subdirectories of $(src) too, without requiring
Makefiles and kbuild to descend to each of them.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Closes: https://lore.kernel.org/r/CAHk-=wjMrqzuUmH-mFbR_46EWEFS=bB=J7h9ABMVy56Vi81PKQ@mail.gmail.com
Fixes: fcbb8461fd23 ("kbuild: remove header compile test")
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

---

Cc: linux-kbuild@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: intel-xe@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
---
 usr/include/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/usr/include/Makefile b/usr/include/Makefile
index e3d6b03527fe..4fb574fd3fec 100644
--- a/usr/include/Makefile
+++ b/usr/include/Makefile
@@ -71,7 +71,7 @@ endif
 # asm-generic/*.h is used by asm/*.h, and should not be included directly
 no-header-test += asm-generic/%
 
-always-y := $(patsubst $(obj)/%.h,%.hdrtest, $(shell find $(obj) -name '*.h' 2>/dev/null))
+always-y := $(patsubst $(obj)/%.h,.hdrtest/%.hdrtest, $(shell find $(obj) -name '*.h' 2>/dev/null))
 
 # Include the header twice to detect missing include guard.
 quiet_cmd_hdrtest = HDRTEST $<
@@ -81,7 +81,7 @@ quiet_cmd_hdrtest = HDRTEST $<
 		$(PERL) $(src)/headers_check.pl $(obj) $<; \
 		touch $@
 
-$(obj)/%.hdrtest: $(obj)/%.h FORCE
+$(obj)/.hdrtest/%.hdrtest: $(obj)/%.h FORCE
 	$(call if_changed_dep,hdrtest)
 
 # Since GNU Make 4.3, $(patsubst $(obj)/%/,%,$(wildcard $(obj)/*/)) works.
-- 
2.39.5