When doing an out-of-tree build, and thus setting VPATH,
GNU Make 3.81 on Ubuntu Trusty complains about Circular dependency of
include/Makefile and include/xlat.lst and drop them. The build fails
later due to headers malformed.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---

Notes:
    v8:
    - make use of the new "$(srcdir)" shortcut
    - move the patch ahead of the problematic patch:
        build: adding out-of-tree support to the xen build

 xen/include/Makefile | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/xen/include/Makefile b/xen/include/Makefile
index 6e80ef276fd9..f64bc293c7f4 100644
--- a/xen/include/Makefile
+++ b/xen/include/Makefile
@@ -45,19 +45,19 @@ public-$(CONFIG_ARM) := $(wildcard $(srcdir)/public/arch-arm/*.h $(srcdir)/publi
 .PHONY: all
 all: $(addprefix $(obj)/,$(headers-y))
 
-$(obj)/compat/%.h: $(obj)/compat/%.i $(src)/Makefile $(srctree)/tools/compat-build-header.py
+$(obj)/compat/%.h: $(obj)/compat/%.i $(srcdir)/Makefile $(srctree)/tools/compat-build-header.py
 	$(PYTHON) $(srctree)/tools/compat-build-header.py <$< $(patsubst $(obj)/%,%,$@) >>$@.new; \
 	mv -f $@.new $@
 
-$(obj)/compat/%.i: $(obj)/compat/%.c $(src)/Makefile
+$(obj)/compat/%.i: $(obj)/compat/%.c $(srcdir)/Makefile
 	$(CPP) $(filter-out -Wa$(comma)% -include %/include/xen/config.h,$(XEN_CFLAGS)) $(cppflags-y) -o $@ $<
 
-$(obj)/compat/%.c: $(src)/public/%.h $(src)/xlat.lst $(src)/Makefile $(srctree)/tools/compat-build-source.py
+$(obj)/compat/%.c: $(src)/public/%.h $(srcdir)/xlat.lst $(srcdir)/Makefile $(srctree)/tools/compat-build-source.py
 	mkdir -p $(@D)
 	$(PYTHON) $(srctree)/tools/compat-build-source.py $(srcdir)/xlat.lst <$< >$@.new
 	mv -f $@.new $@
 
-$(obj)/compat/.xlat/%.h: $(obj)/compat/%.h $(obj)/compat/.xlat/%.lst $(srctree)/tools/get-fields.sh $(src)/Makefile
+$(obj)/compat/.xlat/%.h: $(obj)/compat/%.h $(obj)/compat/.xlat/%.lst $(srctree)/tools/get-fields.sh $(srcdir)/Makefile
 	export PYTHON=$(PYTHON); \
 	while read what name; do \
 		$(SHELL) $(srctree)/tools/get-fields.sh "$$what" compat_$$name $< || exit $$?; \
@@ -65,7 +65,7 @@ $(obj)/compat/.xlat/%.h: $(obj)/compat/%.h $(obj)/compat/.xlat/%.lst $(srctree)/
 	mv -f $@.new $@
 
 .PRECIOUS: $(obj)/compat/.xlat/%.lst
-$(obj)/compat/.xlat/%.lst: $(src)/xlat.lst $(src)/Makefile
+$(obj)/compat/.xlat/%.lst: $(srcdir)/xlat.lst $(srcdir)/Makefile
 	mkdir -p $(@D)
 	grep -v '^[[:blank:]]*#' $< | sed -ne 's,@arch@,$(compat-arch-y),g' -re 's,[[:blank:]]+$*\.h[[:blank:]]*$$,,p' >$@.new
 	$(call move-if-changed,$@.new,$@)
@@ -73,7 +73,7 @@ $(obj)/compat/.xlat/%.lst: $(src)/xlat.lst $(src)/Makefile
 xlat-y := $(shell sed -ne 's,@arch@,$(compat-arch-y),g' -re 's,^[?!][[:blank:]]+[^[:blank:]]+[[:blank:]]+,,p' $(srcdir)/xlat.lst | uniq)
 xlat-y := $(filter $(patsubst compat/%,%,$(headers-y)),$(xlat-y))
 
-$(obj)/compat/xlat.h: $(addprefix $(obj)/compat/.xlat/,$(xlat-y)) $(obj)/config/auto.conf $(src)/Makefile
+$(obj)/compat/xlat.h: $(addprefix $(obj)/compat/.xlat/,$(xlat-y)) $(obj)/config/auto.conf $(srcdir)/Makefile
 	cat $(filter %.h,$^) >$@.new
 	mv -f $@.new $@
 
@@ -100,7 +100,7 @@ PUBLIC_C99_HEADERS := $(addprefix $(public-hdrs-path)/, $(public-c99-headers))
 $(src)/public/io/9pfs.h-prereq := string
 $(src)/public/io/pvcalls.h-prereq := string
 
-$(obj)/headers.chk: $(PUBLIC_ANSI_HEADERS) $(src)/Makefile
+$(obj)/headers.chk: $(PUBLIC_ANSI_HEADERS) $(srcdir)/Makefile
 	for i in $(filter %.h,$^); do \
 	    $(CC) -x c -ansi -Wall -Werror -include stdint.h \
 	          -S -o /dev/null $$i || exit 1; \
@@ -108,7 +108,7 @@ $(obj)/headers.chk: $(PUBLIC_ANSI_HEADERS) $(src)/Makefile
 	done >$@.new
 	mv $@.new $@
 
-$(obj)/headers99.chk: $(PUBLIC_C99_HEADERS) $(src)/Makefile
+$(obj)/headers99.chk: $(PUBLIC_C99_HEADERS) $(srcdir)/Makefile
 	rm -f $@.new
 	$(foreach i, $(filter %.h,$^),                                        \
 	    echo "#include "\"$(i)\"                                          \
@@ -118,7 +118,7 @@ $(obj)/headers99.chk: $(PUBLIC_C99_HEADERS) $(src)/Makefile
 	    || exit $$?; echo $(i) >> $@.new;)
 	mv $@.new $@
 
-$(obj)/headers++.chk: $(PUBLIC_HEADERS) $(src)/Makefile
+$(obj)/headers++.chk: $(PUBLIC_HEADERS) $(srcdir)/Makefile
 	rm -f $@.new
 	if ! $(CXX) -v >/dev/null 2>&1; then                                  \
 	    touch $@.new;                                                     \
-- 
Anthony PERARD

On 25.11.2021 14:39, Anthony PERARD wrote:
> When doing an out-of-tree build, and thus setting VPATH,
> GNU Make 3.81 on Ubuntu Trusty complains about Circular dependency of
> include/Makefile and include/xlat.lst and drop them. The build fails
> later due to headers malformed.

A circular dependency would mean that besides the expected dependency
there is also one of include/Makefile on include/xlat.lst. Where is
that? I'm not aware of anything include/Makefile depends on. Is there
any dependency being introduced in this series, perhaps by way of new
(generated) dependency files? It would be good to have a clear
understanding of the issue - as you describe it, it could as well be
a make flaw.

The adjustments themselves look okay to me, but of course they don't
help readability.

Jan

On Tue, Dec 21, 2021 at 03:16:25PM +0100, Jan Beulich wrote:
> On 25.11.2021 14:39, Anthony PERARD wrote:
> > When doing an out-of-tree build, and thus setting VPATH,
> > GNU Make 3.81 on Ubuntu Trusty complains about Circular dependency of
> > include/Makefile and include/xlat.lst and drop them. The build fails
> > later due to headers malformed.
> 
> A circular dependency would mean that besides the expected dependency
> there is also one of include/Makefile on include/xlat.lst. Where is
> that? I'm not aware of anything include/Makefile depends on. Is there
> any dependency being introduced in this series, perhaps by way of new
> (generated) dependency files? It would be good to have a clear
> understanding of the issue - as you describe it, it could as well be
> a make flaw.

I've got a bunch of:
make[2]: Circular include/compat/arch-x86_32.i <- include/Makefile dependency dropped.


Maybe the issue is with:
    make[2]: Circular include/compat/.xlat/arch-x86/pmu.lst <- include/xlat.lst dependency dropped.
    make[2]: Circular include/compat/.xlat/arch-x86/pmu.lst <- include/Makefile dependency dropped.

with rule
     $(obj)/compat/.xlat/%.lst:  $(src)/xlat.lst $(src)/Makefile

at that mean %.lst have no prerequisite left, so $< is empty in
"grep pattern $<" so there's nothing to grep.

But that doesn't happen every time.

I can't think of anything or find anything which would introduce a
prerequisite for "xlat.lst".

The build seems to work if I only change this rule, to avoid make
looking into VPATH to find $(src)/xlat.lst. Changing this to
"$(srcdir)/xlat.lst" works. But of course, make still complain about
circular dependencies on include/Makefile.

I think I've look for this issue online at the time, but I probably
found the workaround rather than a bug report.

Cheers,

-- 
Anthony PERARD