[Xen-devel] [PATCH for-4.9] xen/test/Makefile: Fix clean target, broken by pattern rule

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

In "xen/test/livepatch: Regularise Makefiles" we reworked
xen/test/Makefile to use a pattern rule.  However, there are two
problems with this.  Both are related to the way that xen/Rules.mk is
implicitly part of this Makefile because of the way that Makefiles
under xen/ are invoked by their parent directory Makefiles.

Firstly, the Rules.mk `clean' target overrides the pattern rule in
xen/test/Makefile.  The result is that `make -C xen clean' does not
actually run the livepatch clean target.

The Rules.mk clean target does have provision for recursing into
subdirectories, but that feature is tangled up with complex object
file iteration machinery which is not desirable here.  However, we can
extend the Rules.mk clean target since it is a double-colon rules.

Sadly this involves duplicating the SUBDIR iteration boilerplate.  (A
make function could be used but the cure would be worse than the
disease.)

Secondly, Rules.mk has a number of -include directives.  make likes to
try to (re)build files mentioned in includes.  With the % pattern
rule, this applies to those files too.

As a result, make -C xen clean would try to build `.*.d' (for example)
in xen/test.  This would fail with an error message.  The error would
be ignored because of the `-', but it's annoying and ugly.

Solve this by limiting the % pattern rule to the targets we expect it
to handle.  These are those listed in the top-level Makefile, apart
from: those which are subdir- or component-qualified; clean targets
(which are handled specially, even distclean); and dist,
src-tarball-*, etc. (which are converted to install by an earlier
Makefile).

Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
---
 xen/test/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/xen/test/Makefile b/xen/test/Makefile
index aa1a23b..aaa4996 100644
--- a/xen/test/Makefile
+++ b/xen/test/Makefile
@@ -7,7 +7,12 @@ ifneq ($(XEN_TARGET_ARCH),x86_32)
 SUBDIRS += livepatch
 endif
 
-%:
+install build subtree-force-update uninstall: %:
        set -e; for s in $(SUBDIRS); do \
                $(MAKE) -f $(BASEDIR)/Rules.mk -C $$s $*; \
        done
+
+clean::
+       set -e; for s in $(SUBDIRS); do \
+               $(MAKE) -f $(BASEDIR)/Rules.mk -C $$s $@; \
+       done
-- 
2.1.4


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