In my pet project, I am using some C++ libraries. The main file/function is also C++. All of it successfully compiles with cmake. Now I want to add some functionality by calling my own D functions (which use some other modules/projects/phobos).

My questions is, what is the "proper" building tool/way.
Do I extend my CMakeFile.txt with additional instructions, which basically do a "dmd -c ...".
Do I use dub to compile the D part as a library, and use that in the cmake file?
Do I use dub to compile the C++ part as well?

Surely somebody has done something similar.
Can you pinpoint me to some examples? I could go from there.

On Wednesday, 29 April 2020 at 10:25:31 UTC, Jan Hönig wrote:
> In my pet project, I am using some C++ libraries. The main file/function is also C++. All of it successfully compiles with cmake. Now I want to add some functionality by calling my own D functions (which use some other modules/projects/phobos).
>
> My questions is, what is the "proper" building tool/way.
> Do I extend my CMakeFile.txt with additional instructions, which basically do a "dmd -c ...".
> Do I use dub to compile the D part as a library, and use that in the cmake file?
> Do I use dub to compile the C++ part as well?
>
> Surely somebody has done something similar.
> Can you pinpoint me to some examples? I could go from there.

LDC is a (somewhat complex) project with D and C++ code (and external C++ libraries).
I think it will help you if your main() is in D (such that druntime is automatically initialized for you).
https://github.com/ldc-developers/ldc

-Johan

On Wednesday, 29 April 2020 at 11:38:16 UTC, Johan wrote:
> LDC is a (somewhat complex) project with D and C++ code (and external C++ libraries).
> I think it will help you if your main() is in D (such that druntime is automatically initialized for you).
> https://github.com/ldc-developers/ldc
>
> -Johan

Hmmm, a D main means i need to do quite some C++ bindings, with which I have 0 experience. I cannot even say if it will be possible.

I will probably need:
https://github.com/jupyter-xeus/xeus/blob/master/include/xeus/xkernel.hpp
https://github.com/jupyter-xeus/xeus/blob/master/include/xeus/xkernel_configuration.hpp
c++ stdlib's unique_ptr.
And then i need to subclass a C++ class and extern this D subclass.

It sounds easier to me, to manually initialize D's runtime (i imagine it being some function calls), build everything with C++, and just call D functions from C++.

Or do you think it is worth the hassle with bindings?

I have done C++ bindings once,years ago in python and it was a not pleasent.

On Wednesday, 29 April 2020 at 13:02:36 UTC, Jan Hönig wrote:
> I will probably need:
Also this thing: https://github.com/nlohmann/json

On Wednesday, 29 April 2020 at 13:02:36 UTC, Jan Hönig wrote:
> On Wednesday, 29 April 2020 at 11:38:16 UTC, Johan wrote:
>> LDC is a (somewhat complex) project with D and C++ code (and external C++ libraries).
>> I think it will help you if your main() is in D (such that druntime is automatically initialized for you).
>> https://github.com/ldc-developers/ldc
>>
>> -Johan
>
> Hmmm, a D main means i need to do quite some C++ bindings, with which I have 0 experience. I cannot even say if it will be possible.
>
> I will probably need:
> https://github.com/jupyter-xeus/xeus/blob/master/include/xeus/xkernel.hpp
> https://github.com/jupyter-xeus/xeus/blob/master/include/xeus/xkernel_configuration.hpp
> c++ stdlib's unique_ptr.
> And then i need to subclass a C++ class and extern this D subclass.
>
> It sounds easier to me, to manually initialize D's runtime (i imagine it being some function calls), build everything with C++, and just call D functions from C++.

Manually initializing D's runtime is also possible. You need to call rt_init and rt_term: https://dlang.org/phobos/core_runtime.html#.rt_init

What I meant is to
- add a `int main(....)` in a D source file
- rename your current `main` in the C++ source file to something like `the_real_main`
- add a forward reference to the D file: `extern(C) int the_real_main(....);`
- call `the_real_main` from the `main` in the D file

That way you don't have to think about how to correctly initialize D's runtime.

-Johan

On Wednesday, 29 April 2020 at 13:12:50 UTC, Johan wrote:
> Manually initializing D's runtime is also possible. You need to call rt_init and rt_term: https://dlang.org/phobos/core_runtime.html#.rt_init
>
> What I meant is to
> - add a `int main(....)` in a D source file
> - rename your current `main` in the C++ source file to something like `the_real_main`
> - add a forward reference to the D file: `extern(C) int the_real_main(....);`
> - call `the_real_main` from the `main` in the D file
>
> That way you don't have to think about how to correctly initialize D's runtime.
>
> -Johan

I thought it was a good idea to ask in the forum!
This actually helps me a lot, thanks!

On Wednesday, 29 April 2020 at 10:25:31 UTC, Jan Hönig wrote:
> In my pet project, I am using some C++ libraries. The main file/function is also C++. All of it successfully compiles with cmake. Now I want to add some functionality by calling my own D functions (which use some other modules/projects/phobos).
>
> My questions is, what is the "proper" building tool/way.
> Do I extend my CMakeFile.txt with additional instructions, which basically do a "dmd -c ...".
> Do I use dub to compile the D part as a library, and use that in the cmake file?
> Do I use dub to compile the C++ part as well?
>
> Surely somebody has done something similar.
> Can you pinpoint me to some examples? I could go from there.

For mixed language project use Cmake only, you do not need to involve dub.

You extend Cmake to compile D files. You add these files with the contents.

CMakeDCompiler.cmake.in:
set(CMAKE_D_COMPILER "@CMAKE_D_COMPILER@")
set(CMAKE_D_COMPILER_LOADED 1)
set(CMAKE_D_SOURCE_FILE_EXTENSIONS @CMAKE_D_SOURCE_FILE_EXTENSIONS@)
set(CMAKE_D_OUTPUT_EXTENSION @CMAKE_D_OUTPUT_EXTENSION@)
set(CMAKE_D_COMPILER_ENV_VAR "@CMAKE_D_COMPILER_ENV_VAR@")


CMakeDetermineDCompiler.cmake:
# Find the D compiler
find_program(
    CMAKE_D_COMPILER
        NAMES "ldc2"
        HINTS "${CMAKE_SOURCE_DIR}"
        DOC "LDC compiler"
)
mark_as_advanced(CMAKE_D_COMPILER)

set(CMAKE_D_SOURCE_FILE_EXTENSIONS d)
set(CMAKE_D_OUTPUT_EXTENSION .obj)
set(CMAKE_D_COMPILER_ENV_VAR "D")

# Configure variables set in this file for fast reload later on
configure_file(${CMAKE_CURRENT_LIST_DIR}/CMakeDCompiler.cmake.in
               ${CMAKE_PLATFORM_INFO_DIR}/CMakeDCompiler.cmake)


CMakeDInformation.cmake:
if(NOT CMAKE_D_COMPILE_OBJECT)
    set(CMAKE_D_COMPILE_OBJECT "<CMAKE_D_COMPILER> ${CMAKE_D_FLAGS} -c --of=<OBJECT> <SOURCE>")
endif()
set(CMAKE_D_INFORMATION_LOADED 1)


CMakeTestDCompiler.cmake:
# For now just do nothing in here
set(CMAKE_D_COMPILER_WORKS 1 CACHE INTERNAL "")


Put these files somewhere and tell Cmake were to find them.

set(CMAKE_MODULE_PATH "${CMAKE_MODULE_PATH}" ${THE_PATH_TO_THE_FILES}" CACHE INTERNAL "")

You need to enable D language to use it with.

enable_language(D)



You can make this more complex but this will make you start quickly. Now Cmake will compile D files as soon as it encounters source files with the .d extension. You can gladly mix C++ and D files and it will link them all together.