[CMake] using ExternalProject_Add when cmake is launched

[Petr Kmoch]

Hi Stephane.

ExternalProject is designed to run at *build* time, not at *CMake* time. It
is not really intended for mixing with normal, non-ExternalProject targets
(such as those created by add_library).

When using ExternalProject, the canonical form of operation is a
SuperBuild-style project: your master CMakeLists.txt will contain only
ExternalProject_Add() calls, *including one for your normal project.* Your
normal project becomes just another project managed by the SuperBuild. The
SuperBuild's purpose is to download, configure, build, etc., all the
subprojects. So you generate the SuperBuild and then build it once to get
all the dependencies in place. The you switch to using just the YourProject
"child" of the SuperBuild and do normal development there.

I think googling "CMake ExternalProject_Add superbuild" will give you
enough details to get you going.

Petr

On 2 May 2018 at 10:31, Stéphane Ancelot <sancelot at numalliance.com> wrote:

> include(ExternalProject)
>
> ExternalProject_Add(
>     WIN32DEPSV2
>     PREFIX ${CMAKE_CURRENT_BINARY_DIR}/WIN32DEPSV2
>     DOWNLOAD_DIR .
>     STAMP_DIR ./stamps
>     SOURCE_DIR   WIN32DEPSV2
>     GIT_REPOSITORY git at numagit.numalliance.com:THIRD_PARTIES/WIN32DEPS.git
>     CONFIGURE_COMMAND ""
>     BUILD_COMMAND ""
>     BUILD_IN_SOURCE 1
>     INSTALL_COMMAND ""
> )
>
> add_library(your_other_target ...)
>
> add_dependencies(your_other_target WIN32DEPSV2)
>
> find_package(Freetype REQUIRED QUIET)
>
> Launching cmake does not clone the git folder , but continues and fails
> with the find_package command
>
> CMake Error at /usr/local/cmake-3.10.3-Linux-x86_64/share/cmake-3.10/
> Modules/FindPackageHandleStandardArgs.cmake:137 (message):
>   Could NOT find Freetype (missing: FREETYPE_LIBRARY FREETYPE_INCLUDE_DIRS)
> Call Stack (most recent call first):
>   /usr/local/cmake-3.10.3-Linux-x86_64/share/cmake-3.10/Modules/
> FindPackageHandleStandardArgs.cmake:378 (_FPHSA_FAILURE_MESSAGE)
>   /usr/local/cmake-3.10.3-Linux-x86_64/share/cmake-3.10/Modules/FindFreetype.cmake:157
> (find_package_handle_standard_args)
>   FOX64/CMakeLists.txt:919 (find_package)
>
> Le 02/05/2018 à 09:32, Kai Wolf a écrit :
>
> You probably need to manually add a dependency from your ExternalProject
> to your target that needs the libraries.
> For instance
>
>     ExternalProject_Add(fetch_win32_libs ...)
>     add_library(your_other_target ...)
>
>
> Greetings
>
> Kai Wolf
>
> http://kai-wolf.me/
> kai.wolf at gmail.com
>
> 2018-05-02 8:47 GMT+02:00 Stéphane Ancelot <sancelot at numalliance.com>:
>
>> Hi,
>>
>> I have got some win32 libraries dependencies stored in a project .
>>
>> Then I added ExternalProject_Add at beginning of my cmakelists file in
>> order to clone this dependency to be available.
>>
>> and then provide the root path as follow:
>>
>> SET(CMAKE_FIND_ROOT_PATH /usr/i586-mingw32msvc
>> ${CMAKE_CURRENT_SOURCE_DIR}/WIN32DEPS/JPEGLIB/jpegsrc-9c
>> ${CMAKE_CURRENT_SOURCE_DIR}/WIN32DEPS/zlib-1.2.3-lib
>> ${CMAKE_CURRENT_SOURCE_DIR}/WIN32DEPS/libpng-1.2.37-lib
>> ${CMAKE_CURRENT_SOURCE_DIR}/WIN32DEPS/ftgl-binary
>> ${CMAKE_CURRENT_SOURCE_DIR}/WIN32DEPS/freetype-dev_2.4.2-1
>> ${CMAKE_CURRENT_SOURCE_DIR}/WIN32DEPS/iconv-1.9.2.1
>>                         )
>>
>>
>> unfortunately, the project is not cloned when cmake is launched and the
>> next dependencies don't find the packages :-(
>>
>> What Can I do ?
>>
>> Regards,
>>
>> S.Ancelot
>> --
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>
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>
> Powered by www.kitware.com
>
> Please keep messages on-topic and check the CMake FAQ at:
> http://www.cmake.org/Wiki/CMake_FAQ
>
> Kitware offers various services to support the CMake community. For more
> information on each offering, please visit:
>
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>
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