Hello Simon,
I was thinking about the comment in $(TOP)/libraries/Makefile:27-30:
# make doesn't give us an easy way to get the libraries built in
# dependency order the first time, but not rebuild base (for example)
# when we want to rebuild another library later.
# So for now we just don't do anything in parallel in here.
due to running over a list when you need to show Make the list as a
set of dependancies. It is not noted in $(TOP)/Makefile but that has
the same problem for Make; it does not manifest itself because it is
hidden by a shell script:
$(TOP)/Makefile:92-98:
for i in $(SUBDIRS_BUILD); do \
echo
"-----------------------------------------------------------------------
-"; \
echo "== $(MAKE) boot $(MFLAGS);"; \
echo " in $(shell pwd)/$$i"; \
echo
"-----------------------------------------------------------------------
-"; \
$(MAKE) --no-print-directory -C $$i $(MFLAGS) boot; \
if [ $$? -eq 0 -o $$x_on_err -eq 0 ] ; then true; else exit 1; fi; \
There is a good solution for this that, as I have tested it, works
with GNU Make 3.80 (you do not need 3.81): do a recursive eval for
the targets so, as Make evaluates each target in the list it produces
a rule. (This would also eliminate the 'for' block in $(TOP)/
Makefile.) Here is a simple demonstration:
--- test Makefile
dirs := one two three four five six
.PHONY : all
all : $(dirs)
% : $(dirs)
# $(call one_target,target)
define one_target
$(1) :
@echo "$(1)"
endef
# for $(word n,text), if n > num words, evaluates to empty
# $(call depend_rec,first_target,rest)
define depend_rec
$$(eval $$(if $$(word 2, $(2)),\
$$(call depend_rec,\
$$(firstword $(2)),$$(wordlist 2, $$(words $(2)), $(2))),\
$$(call one_target,$(2))))
$(1) : $(2)
@echo "$(1)"
endef
$(eval $(call depend_rec,$(firstword $(dirs)),\
$(wordlist 2,$(words $(dirs)),$(dirs))))
--- end test Makefile
At the end of this Make will have created targets for each of the
items in the list in reverse order:
six :
[commands]
five : six
[commands]
...
one : two three four five six
[commands]
Following this, Make would easily be able to handle building in
parallel for libraries/Makefile. If you like the idea I will
implement it and send a patch. The only catch is the base Make
version required would go up to 3.80.
Cheers,
Pete
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