On Sat, Apr 9, 2011 at 2:32 PM, Philip Prindeville
<phil...@redfish-solutions.com> wrote:
> [philipp@builder ~/openwrt2]$ make -j5 -f /tmp/Makefile
> MAKEFLAGS=
> MFLAGS=
> MAKE=make
> PBUILD=
> MAKEFLAGS=w
> MFLAGS=-w
> MAKE=make
> make[1]: Entering directory `/home/philipp/openwrt2'
> make[1]: Nothing to be done for `stop'.
> make[1]: Leaving directory `/home/philipp/openwrt2'
> [philipp@builder ~/openwrt2]$
>
> Not sure what I'm missing...
Unfortunately it appears that MAKEFLAGS is composed on the fly when
forking a command (aka job). See the following makefile:
% cat /tmp/Makefile
$(info MAKEFLAGS='$(MAKEFLAGS)')
.PHONY: all
all:
@echo "MAKEFLAGS='$(MAKEFLAGS)' (recipe)"
% make -f /tmp/Makefile -j2
MAKEFLAGS=''
MAKEFLAGS=' --jobserver-fds=3,4 -j' (recipe)
So it's not available to $(info) and other functions outside of a
recipe. There's probably a way to trick make into doing a simple
recursion to harvest the data. Or if you're dealing with an
automated/nightly build you could set MAKEFLAGS yourself to turn on
parallelism:
MAKEFLAGS=-j8 make ...
but at that point you might as well just take control yourself
PARALLEL=YES make -j8 ...
Here's a hack which will work by calling make recursively once, but
note that it will only work when no explicit target is mentioned:
% cat Makefile
.PHONY: all
all:
ifndef PARALLEL
.PHONY: _is_parallel
.DEFAULT_GOAL := _is_parallel
_is_parallel:
+@PARALLEL=`PARALLEL=tbd $(MAKE) -s -f $(MAKEFILE_LIST)
_is_parallel2` &&\
PARALLEL=$$PARALLEL $(MAKE) --no-print-directory -f
$(MAKEFILE_LIST) $(MAKECMDGOALS)
else
.PHONY: _is_parallel2
_is_parallel2: ; @echo "$(if $(findstring -j,$(MAKEFLAGS)),YES,NO)"
endif
all:
@echo "We $(if $(findstring YES,$(PARALLEL)),ARE,ARE NOT)
building in parallel"
David Boyce
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