A library to convert any C++ callable into a C function pointer using a dynamically generated libffi trampoline.

#include <voidstar.h>

// Third-party library
extern "C" {
  typedef int (*example_callback)(float);
  void example_function(example_callback);
}

int main() {
  float param;
  int result = 42;

  auto closure =
    voidstar::make_closure<example_callback>([&](float p) {
      param = p;
      return result;
    });

  // No global or thread_local variables
  example_function(closure.get());

  // example_callback works until `closure` is destroyed
}

Check out a more complete example or see full library reference.

The library is implemented and tested on amd64 Linux with g++ 12 and clang++-14. It has not yet been used in a real production environment.

Compile-time features tested with g++-11, -12, -13, clang++-14, -18, MSVC 19, libffi 3.4.2, 3.4.4, 3.4.6.

• Struct layout guessing via structured bindings (Boost.PFR?)

sudo apt install g++ make cmake
sudo apt install libffi-dev libgtest-dev
cmake -B build
cmake --build build

conan install . -s build_type=Debug --build=missing
cmake --preset conan-debug
cmake --build --preset conan-debug

On systems with CMake version below 3.23, --preset won't work. See output of conan install for details.

See also Conan recipe for repositories in packaging/conan/.