nim host and guest

host.cpp

#include <iostream>
#include <dlfcn.h>


typedef void (*target_t)();

void target()
{
  std::cout << "host: target\n";
}

int main() {
  void *handle;
  typedef void (*init_t)(target_t);
  init_t init;
  const char *err;
  
  handle = dlopen("plugin.cpp.so", RTLD_NOW);
  init = (init_t) dlsym(handle, "init");
  err = dlerror();
  if (err) {
    std::cerr << "dlsym failed: " << err << '\n';
    return 1;
  }
  init(&target);
  dlclose(handle);

  handle = dlopen("plugin.nim.so", RTLD_NOW);
  init = (init_t) dlsym(handle, "init");
  err = dlerror();
  if (err) {
    std::cerr << "dlsym failed: " << err << '\n';
    return 1;
  }
  init(&target);
  dlclose(handle);

  return 0;
}

Makefile

all: host plugin.cpp.so plugin.nim.so

host: host.cpp
	g++ host.cpp -ldl -o host

plugin.cpp.so: plugin.cpp
	g++ -fpic -c plugin.cpp -o plugin.o
	g++ -shared -o plugin.cpp.so plugin.o

plugin.nim.so: plugin.nim
	nim cpp --app=lib -o:plugin.nim.so plugin.nim

clean:
	rm -f plugin.cpp.so plugin.nim.so plugin.o host nimcache/*
	rmdir nimcache

plugin.cpp

#include <iostream>

typedef void (*target_t)();

extern "C" {
  void init(target_t target) {
    std::cout << "plugin.cpp: init\n";
    target();
  }
}

plugin.nim

type
  target_t* = proc ()

proc init(target: target_t) {.cdecl,exportc,dynlib.} =
  echo "plugin.nim: init"
  target()