[CMake] adding external project

[Nicholas Braden]

I think the issue you are running into is order of execution - when
using external projects it is often a good idea to have all the
ExternalProject_Add commands in a superproject file with your own
project source directory as one of the external projects. This way you
can use the DEPENDS parameter to guarantee order of execution - this
also makes it so people can just build your project from the source
directory if they already have the dependencies, and you can use
things like find_package and such.

On Tue, Dec 15, 2015 at 4:57 AM, Owen Hogarth II <gurenchan at gmail.com> wrote:
> oh, that was it a typo!
>
> A few more questions. I build the project like this:
> ExternalProject_Add(sdl
>     HG_REPOSITORY http://hg.libsdl.org/SDL
>     UPDATE_COMMAND ""
>
>     CMAKE_ARGS -DSDL_STATIC:BOOL=FALSE
>     -DCMAKE_INSTALL_PREFIX:PATH=${CMAKE_BINARY_DIR}/lib
>
>     SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/SDL
>
>     INSTALL_DIR ${CMAKE_CURRENT_BINARY_DIR}/bin
>     )
>
> That seems to build everything and put everything in the right place.
> Another thing that I did with other parts of my code was add these lines to
> the end of the cmakelists.txt files
>
> TARGET_INCLUDE_DIRECTORIES(mylib PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/headers)
>
> so that I can just #include "mylib" instead of the path to the file. With
> this setup, I can't do target_include_directories from the
> external_project_add command, how do I get those headers?
>
> On Tue, Dec 15, 2015 at 6:26 PM, Nicholas Braden
> <nicholas11braden at gmail.com> wrote:
>>
>> What's the word "clone" doing in there? That should be a URL, not
>> command parameters.
>>
>> On Tue, Dec 15, 2015 at 2:01 AM, Owen Hogarth II <gurenchan at gmail.com>
>> wrote:
>> > I have been reading this:
>> > https://cmake.org/cmake/help/v3.0/module/ExternalProject.html
>> >
>> > trying to add sdl external project but I am  having issues. I created a
>> > new
>> > cmake project to test.
>> >
>> > I already downloaded the sdl library and can build it correctly by
>> > manually
>> > calling cmake commands but this is how I'd like to distribute sdl w/ my
>> > library.
>> >
>> > here's my new test cmake:
>> >
>> > cmake_minimum_required(VERSION2.8)
>> > project(sdl_external)
>> >
>> > include(ExternalProject)
>> >
>> > ExternalProject_Add(sdl
>> >     HG_REPOSITORY clone http://hg.libsdl.org/SDL
>> >     # PREFIX ${CMAKE_SOURCE_DIR}/sdl
>> >
>> >     # SOURCE_DIR ${CMAKE_SOURCE_DIR}/sdl
>> >
>> >     # INSTALL_COMMAND cmake ../ PREFIX=${CMAKE_CURRENT_BINARY_DIR}
>> >     )
>> >
>> > I get this build output:
>> > cmake ../
>> > -- The C compiler identification is GNU 4.9.2
>> > -- The CXX compiler identification is GNU 4.9.2
>> > -- Check for working C compiler: /usr/bin/cc
>> > -- Check for working C compiler: /usr/bin/cc -- works
>> > -- Detecting C compiler ABI info
>> > -- Detecting C compiler ABI info - done
>> > -- Check for working CXX compiler: /usr/bin/c++
>> > -- Check for working CXX compiler: /usr/bin/c++ -- works
>> > -- Detecting CXX compiler ABI info
>> > -- Detecting CXX compiler ABI info - done
>> > -- Found Hg: /usr/bin/hg (found version "3.1.2")
>> > -- Configuring done
>> > -- Generating done
>> > -- Build files have been written to: /home/blubee/sdk/test/build
>> > Scanning dependencies of target sdl
>> > [ 12%] Creating directories for 'sdl'
>> > [ 25%] Performing download step (hg clone) for 'sdl'
>> > -- Avoiding repeated hg clone, stamp file is up to date:
>> > '/home/blubee/sdk/_b/build/test/
>> > build/sdl-prefix/src/sdl-stamp/sdl-hginfo.txt'
>> > [ 37%] No patch step for 'sdl'
>> > [ 50%] Performing update step (hg pull) for 'sdl'
>> > abort: no repository found in '
>> > /home/blubee/sdk/test/build/sdl-prefix/src/sdl' (
>> > .hg not found)!
>> > CMakeFiles/sdl.dir/build.make:89: recipe for target
>> > 'sdl-prefix/src/sdl-stamp/sdl-update'
>> >  failed
>> > make[2]: *** [sdl-prefix/src/sdl-stamp/sdl-update] Error 255
>> > CMakeFiles/Makefile2:60: recipe for target 'CMakeFiles/sdl.dir/all'
>> > failed
>> > make[1]: *** [CMakeFiles/sdl.dir/all] Error 2
>> > Makefile:76: recipe for target 'all' failed
>> > make: *** [all] Error 2
>> >
>> > my external build file isn't very verbose but I don't get the error
>> >
>> > why is it reporting that no repository found.
>> > abort: no repository found in
>> > '/home/blubee/sdk/test/build/sdl-prefix/src/sdl' (
>> > .hg not found)!
>> >
>> > Why isn't the mercurial project not being downloaded?
>> >
>> > --
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