I can finally give a good concrete case where I might need to do this (or
need some other very clever solution).
I have created a distcheck command for BRL-CAD that has a lot of
responsibilities, including doing a complete configure and build of BRL-CAD
from a source archive expanded from a CPack tarball. The distcheck rule
uses cmake to fire off the build (this is to try and be future proof against
using other tools than Make to do a distcheck) but I need to pass the
parallel build setting -j from Make down to the ${CMAKE_COMMAND} build
launched by the distcheck rule, and there doesn't seem to be any way to do
it.
This is the subset of the distcheck rule (somewhat edited for clarity):
ADD_CUSTOM_TARGET(distcheck
COMMAND ${CMAKE_COMMAND} -E echo "Stage 1: Create source tgz, tbz2
and zip archives from toplevel archive."
COMMAND cpack --config
${CMAKE_CURRENT_BINARY_DIR}/CPackSourceConfig.cmake
COMMAND ${CMAKE_COMMAND} -E echo "Stage 2: Expand tgz archive and
prepare to build from archive sources."
COMMAND ${CMAKE_COMMAND} -E tar xvzf
${CPACK_SOURCE_PACKAGE_FILE_NAME}.tar.gz
COMMAND ${CMAKE_COMMAND} -E make_directory
_${CPACK_SOURCE_PACKAGE_FILE_NAME}-build
COMMAND ${CMAKE_COMMAND} -E make_directory
_${CPACK_SOURCE_PACKAGE_FILE_NAME}-install
COMMAND ${CMAKE_COMMAND} -E chdir
_${CPACK_SOURCE_PACKAGE_FILE_NAME}-build ${CMAKE_COMMAND}
../${CPACK_SOURCE_PACKAGE_FILE_NAME}
-DCMAKE_INSTALL_PREFIX=${CMAKE_CURRENT_BINARY_DIR}/_${CPACK_SOURCE_PACKAGE_FILE_NAME}-install
COMMAND ${CMAKE_COMMAND} -E echo "Stage 3: Compile using source from
tgz archive."
COMMAND ${CMAKE_COMMAND} --build
_${CPACK_SOURCE_PACKAGE_FILE_NAME}-build
)
This can be successfully fired off by "make distcheck", which is the desired
behavior. However, the --build option doesn't respect (naturally) any -jN
options fed to make, since they aren't specified at CMake time when the
distcheck Makefile target is being generated.
Perversely enough, if I'm understanding the issue correctly I won't be able
to use the -jN value itself in any case, even if the Makefile can be taught
to do something smart:
http://old.nabble.com/MAKEFLAGS-var-does-not-show-%22-j%22-param-----td15983337.html
The best idea I can come up with so far is for the CMake generated Makefile
to write out a variable containing some CPU related variable (e.g. make
CPUS=8 and write the value of $(CPUS) to CMakeFiles/make_cpu_flag or some
such) and then convert the distcheck commands above into a series of
EXECUTE_PROCESS lines in a rundistcheck.cmake file that is launched by the
distcheck rule with a ${CMAKE_COMMAND}. In rundistcheck.cmake, I can check
for the presence of the make_cpu_flag file and if found add the -j parallel
flag to the --build line before running it. That will mean a parallel
distcheck will have to use a different make syntax than the standard make
-j, but at least it would be something. Unfortunately, that means I still
need the Makefile to let me know what was passed in up front, which means
tweaking the CMake generated output somehow (not really sure how yet).
Does anybody else have a mechanism for passing parallel build instructions
from make down to child ${CMAKE_COMMAND} --build instances?
Cheers,
CY
On Wed, Feb 2, 2011 at 4:32 PM, Michael Hertling <mhertl...@online.de>wrote:
> On 02/02/2011 03:34 PM, Clifford Yapp wrote:
> > Is there any way to customize the Makefile output from CMake to
> > include user-defined lines (say, something like "#include
> > Makefile.inc") at the end of each Make file?
>
[snip]
> However, this approach is neither portable nor clean
> nor <your-expectation-here>, so I would ask Eric's questions, too. ;)
>
> Regards,
>
> Michael
>
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