Hello,

I am trying to compile an application with both C++ and D source code.

First I have main.d:

extern (C++) void init();
extern (C++) void draw(int row, int column, int x, int y);
extern (C++) void render();

void main() {
    init();
    draw(3, 3, 0, 0);
    draw(3, 3, 2, 2);
    draw(3, 3, 1, 1);
    render();
}

And I have viewer.cpp:

void init() { ... }
void draw() { ... }
void render() { ... }

Lastly, I have CMakeLists.txt:

cmake_minimum_required (VERSION 3.0)
set(CMAKE_BUILD_TYPE Debug)

# Below line is for using C++14 standard
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")

# Our project name
project (framework)

add_executable(framework main.o viewer.cpp)

# DLang
#INCLUDE(main.o)

# For finding our SDL2 package!
INCLUDE(FindPkgConfig)

# Searching SDL2 package.
PKG_SEARCH_MODULE(SDL2 REQUIRED sdl2)

# Including our external library's directory for header files!
INCLUDE_DIRECTORIES(${SDL2_INCLUDE_DIRS})

# Linking SDL2 library with our project.
target_link_libraries(framework ${SDL2_LIBRARIES})

I execute the following lines in my terminal:

dmd -c main.d
cd build
cmake ..
make

And I get this error:

/usr/bin/ld: ../main.o: in function `main':
main.d:(.text.main[main]+0xc): undefined reference to `_d_run_main'
/usr/bin/ld: ../main.o:(.text.d_dso_init[.data.d_dso_rec]+0x22): undefined reference to `_d_dso_registry'

So something goes wrong with linking, but I dont know what.

On Thursday, 4 August 2022 at 20:29:30 UTC, Jan Allersma wrote:

Execute dmd -v on some test program. It will output the linker line at the end of the output, the line starting with cc yourcode.o -o yourcode .... On that linker line you will see what libraries to add in your CMake script, such that when linking the C++ program and D object files, it pulls in the libraries that D expects (standard library).

cheers,
Johan

On Thursday, 4 August 2022 at 20:59:50 UTC, Johan wrote:

It's nice feature in D that we can mix C code with it, because I know C is so jealous language.

On Thursday, 4 August 2022 at 20:59:50 UTC, Johan wrote:

Thanks Johan!
All I needed to do was to pass phobos2 as argument for target_link_libraries.

Now I am getting some errors on running:

double free or corruption (fasttop)
Afgebroken (geheugendump gemaakt)

But that is an issue about something completely different, I presume. Thanks for the help!

I forgot that I have to add some DUB dependencies. So I have to use dub instead of dmd.
My strategy is to

1. Create a D function which will be called in C++.
2. Build a static library containing the D function (using dub build).
3. Build an executable file with CMake.

However, I get an ld error:

/usr/bin/ld: ../libhello-sdl.a(app_1_144.o):(.text.d_dso_init[.data.d_dso_rec]+0x22): undefined reference to `_d_dso_registry'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/framework.dir/build.make:85: framework] Fout 1
make[1]: *** [CMakeFiles/Makefile2:76: CMakeFiles/framework.dir/all] Fout 2
make: *** [Makefile:84: all] Fout 2

I do not know what _d_dso_registry is. Therefore, I don't know how to solve this problem.

On Saturday, 6 August 2022 at 13:52:28 UTC, Jan Allersma wrote:

/usr/bin/ld: ../libhello-sdl.a(app_1_144.o):(.text.d_dso_init[.data.d_dso_rec]+0x22): undefined reference to `_d_dso_registry'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/framework.dir/build.make:85: framework] Fout 1
make[1]: *** [CMakeFiles/Makefile2:76: CMakeFiles/framework.dir/all] Fout 2
make: *** [Makefile:84: all] Fout 2

I figured out a strategy to solve te problem:

1. Create a C++ function which will be called in D.
2. Build a static C++ library with CMake and add dependencies (In my case: SDL libraries)
3. Create a new project (dub init).
4. Add these lines to dub.json:

	"dflags": ["-L-lstdc++"],
	"lflags": ["-Lbuild", "-lframework", "-lSDL2"],

• -L-lstdc++ is needed to use standard C++ functions.
• -Lbuild is to add the build directory a library path (this is the directory where my earlier compiled C++ library is in).
• -lframework is used to link my earlier compiled C++ library libframework.a.
• And finally -lSDL2 because that is a dependency used by my C++ library.

Now I can add dependencies for my D code as well using dub add!

On Saturday, 6 August 2022 at 18:22:45 UTC, Jan Allersma wrote:

	"dflags": ["-L-lstdc++"],
	"lflags": ["-Lbuild", "-lframework", "-lSDL2"],

Thank you for posting the solution! And you were fast enough to find
it yourself before anyone can arrive with the solution ;)

Happy coding my friend!