[CMake] ExternalProject_Add, dependencies and Make

[Ben Pope]

On 04/07/13 04:15, Brad King wrote:
> On 07/02/2013 11:59 PM, Ben Pope wrote:
>> I've got a number of libraries I depend on, I use ExternalProject_Add to 
>> ./configure and build them, I set the DEPENDS field to another 
>> ExternalProject_Add target.
> 
> We do this commonly and use "make -j" to build multiple external
> projects in parallel subject to their dependencies.  The DEPENDS
> option should say "bring the dependency completely up to date
> before starting to build the dependent".
> 
> Can you post an example CMakeLists.txt, along with the cmake and
> make command lines you use to build it?

Yeah, I figured out what caused it and how to fix it:

*****
cmake_minimum_required (VERSION 2.8)

project(parallel_build_test)

include (ExternalProject)

ExternalProject_Add(parallel
	DOWNLOAD_COMMAND sleep 1
	CONFIGURE_COMMAND sleep 1
	BUILD_COMMAND sleep 1
	INSTALL_COMMAND touch parallel
)

ExternalProject_Add(depends1
	DOWNLOAD_COMMAND sleep 1
	CONFIGURE_COMMAND sleep 1
	BUILD_COMMAND sleep 1
	INSTALL_COMMAND touch depends1
	DEPENDS parallel
)

ExternalProject_Add(project1
	DOWNLOAD_COMMAND sleep 1
	CONFIGURE_COMMAND sleep 1
	BUILD_COMMAND sleep 1
	INSTALL_COMMAND touch project1
	DEPENDS depends1
)

ExternalProject_Add(depends2
	DOWNLOAD_COMMAND sleep 1
	CONFIGURE_COMMAND sleep 1
	BUILD_COMMAND sleep 1
	INSTALL_COMMAND touch depends2
	DEPENDS parallel
)

ExternalProject_Add(project2
	DOWNLOAD_COMMAND sleep 1
	CONFIGURE_COMMAND sleep 1
	BUILD_COMMAND sleep 1
	INSTALL_COMMAND touch project2
	DEPENDS depends2
)

add_custom_target(build_stuff
	DEPENDS project1 project2
)
*****

make -j project1 project2 # BROKEN (also reaches 158% complete :P)
make -j build_stuff       # fine


The only problem now is that the output is interleaved, I might see
something like:
[ 78%] [ 78%] [ 80%] [ 80%] [ 80%] [ 81%] Building....

But I guess that's for performance reasons?

Ben