CMake ExternalProject_Add and parallel builds - c++

Question

With the following CMakeLists.txt build script:
include( ExternalProject )
ExternalProject_Add( framework SOURCE_DIR ${framework_SOURCE}
PREFIX framework_build
INSTALL_DIR ${framework_DISTRIBUTION} )
...
add_library( ${PROJECT_NAME} SHARED ${BUILD_MANIFEST} )
add_dependencies( ${PROJECT_NAME} framework )
When I attempt to perform a parallel build (make -j5) it will occasionally fail due to a build artefact from the framework not being present. The order of the build, fixed by add_dependencies, is not being adhered to.
Have I misunderstood the documentation around add_dependencies?
Output from cmake --graphviz=graph.dot

Answer 1

Ok, so an updated version of CMake has warned me that the framework dependency is not present. ExternalProject_Add and add_dependencies can not be used with each other, as ExternalProject_Add has not actually built and therefore registered the framework as a high-level target.
Note:
Anyone encountering this problem in future. I've found another SO post by #matiu that resolved my issue.

Answer 2

Maybe ExternalProject_Add_StepDependencies could solve that and create a dependency between the externalproject_add and the imported target?

Answer 3

This is a minimal working example adding Google test as a dependency.
cmake_minimum_required(VERSION 2.8)
project(ExampleProject)
# Set the build type if it isn't already
if(NOT CMAKE_BUILD_TYPE)
set(CMAKE_BUILD_TYPE Debug)
endif()
include(ExternalProject)
set(GOOGLE_TEST GoogleTest)
set(GTEST_PREFIX "${CMAKE_CURRENT_BINARY_DIR}/${GOOGLE_TEST}")
ExternalProject_Add(${GOOGLE_TEST}
GIT_REPOSITORY https://chromium.googlesource.com/external/googletest
PREFIX ${GTEST_PREFIX}
CMAKE_ARGS -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
INSTALL_COMMAND ""
)
# Specify include directory
ExternalProject_Get_Property(${GOOGLE_TEST} source_dir)
include_directories(${source_dir}/include)
set(LIBPREFIX "${CMAKE_STATIC_LIBRARY_PREFIX}")
set(LIBSUFFIX "${CMAKE_STATIC_LIBRARY_SUFFIX}")
set(GTEST_LOCATION "${GTEST_PREFIX}/src/${GOOGLE_TEST}-build")
set(GTEST_LIBRARY "${GTEST_LOCATION}/${LIBPREFIX}gtest${LIBSUFFIX}")
set(EXECUTABLE_NAME ${CMAKE_PROJECT_NAME})
add_executable(${EXECUTABLE_NAME} main.cpp)
add_dependencies(${EXECUTABLE_NAME} ${GOOGLE_TEST})
target_link_libraries(
${EXECUTABLE_NAME}
${GTEST_LIBRARY}
-lpthread
)
enable_testing()
set(TEST_NAME ${EXECUTABLE_NAME})
add_test(${EXECUTABLE_NAME} ${TEST_NAME})
And this is the dependency graph:
In this case without add_dependencies a parallel build will always fail, because of missing the dependency.