[CMake] Create main and sub-projects; be able to compile them together and individually.

[Nicholas Braden]

Example simple usages from my personal projects:
https://github.com/LB--/events/blob/499ba78b923b40f77cc832b6a5d414240209ac96/CMakeLists.txt
https://github.com/LB--/simple-platformer/blob/1bba3dd2d8ed1cdae74ce1b77c4ab99878fa59a6/CMakeLists.txt

More complex usage in hunter:
https://github.com/ruslo/hunter

With ExternalProject you can have it either download from version control /
source archive, or you can use a local existing folder. I think in your
case you just need to point it to your existing project folders and forward
the appropriate arguments. There is a lot of customizability to it
(customizing each step, for example). If you want I could make an example
exactly like your provided example directory structure, but I think both of
my personal usages closely match what you are wanting to do.

On Tue, Mar 8, 2016 at 7:02 PM, Muhammad Osama <osama94 at gmail.com> wrote:

> Thank you for your suggestion Nicholas, I have never used
> ExternalProject_Add before and can't find a related example to my project.
> Would you know an example that uses it?
>
> On Tue, Mar 8, 2016 at 10:38 AM, Nicholas Braden <
> nicholas11braden at gmail.com> wrote:
>
>> Have you looked into ExternalProject_Add? It allows just using a local
>> path instead of downloading a remote repository:
>>
>> https://cmake.org/cmake/help/latest/module/ExternalProject.html
>>
>> On Tue, Mar 8, 2016 at 12:12 PM, Muhammad Osama <osama94 at gmail.com>
>> wrote:
>>
>>> Hi Jan,
>>>
>>> Thank you for your reply, I am in the similar situation, have a very
>>> similar implementation using *target_*** *but since I don't do that for
>>> ALL the dependencies, I am unable to cmake or compile individual projects
>>> in the sub directories. So, few questions;
>>>
>>> 1. This still requires me to run cmake on the root CMakeLists.txt to set
>>> the flags and what not before I run the sub project to make it correct?
>>> 1a. If so, how can I make the CMakeLists.txts in the sub directories
>>> independent of the root one if I want to just compile the sub-project and
>>> not cmake the whole thing?
>>> 2. Another question is that your implementation, does it not include a
>>> config file? In theory you're copy pasting most of the dependencies in the
>>> CMakeLists.txt of root into the sub-dir ones? Is there a better way to do
>>> this?
>>>
>>> Thank you!
>>>
>>> On Tue, Mar 8, 2016 at 2:02 AM, 🐋 Jan Hegewald <jan.hegewald at awi.de>
>>> wrote:
>>>
>>>> Hi Muhammad,
>>>>
>>>> > On 08.03.2016, at 06:17, Muhammad Osama <osama94 at gmail.com> wrote:
>>>> >
>>>> > Hi, I am new to cmake and really hope am doing this correctly. I
>>>> asked stackoverflow but didn't get a good enough answer for my specific
>>>> problem here;
>>>> >
>>>> > If I want root/sub-directories/ as separate sub-projects that can be
>>>> compiled using the individualCMakeLists.txts in their folders I find myself
>>>> literally copy pasting almost the entire root file CMakeLists.txt per
>>>> sub-directory.
>>>> >
>>>> > I was wondering if there is a better way to have a main project and
>>>> then sub-projects that get the shared dependencies from main project and
>>>> can be compiled without cmake-ing the root CMakeLists.txt. My directory
>>>> structure is;
>>>> >
>>>> > CMakeLists.txt (root project)
>>>> > | __ sub_dir-1
>>>> > | __ | __ CMakeLists.txt (sub-project)
>>>> > | __ sub_dir-2
>>>> > | __ | __ CMakeLists.txt (sub-project)
>>>> > | __ sub_dir-3
>>>> > | __ | __ CMakeLists.txt (sub-project)
>>>>
>>>> I basically have the same project structure as you describe. I am also
>>>> not sure what the best practice is here, but this is what I currently do:
>>>> I set all dependencies where they are required: right in the local
>>>> CMakeLists.txt, i.e. sub_dir-1/CMakeLists.txt. Then "export" all required
>>>> include/define/compiler flags dependencies via INTERFACE or PUBLIC flags of
>>>> the various target_*** cmake functions, as appropriate. The sub-projects
>>>> are added via add_subdirectory in cmake.
>>>> This way I can build each CMakeLists.txt individually if needed but
>>>> still have everything DRYish.
>>>>
>>>> HTH,
>>>> Jan
>>>>
>>>> --
>>>>
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>>>
>>>
>>>
>>> --
>>> *Muhammad Osama*
>>> Graduate Student
>>> Department of Electrical and Computer Engineering
>>> University of California, Davis
>>>
>>> --
>>>
>>> Powered by www.kitware.com
>>>
>>> Please keep messages on-topic and check the CMake FAQ at:
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>>>
>>> Kitware offers various services to support the CMake community. For more
>>> information on each offering, please visit:
>>>
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>>
>>
>
>
> --
> *Muhammad Osama*
> Graduate Student
> Department of Electrical and Computer Engineering
> University of California, Davis
>
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