Neko Dlls in Haxe C++ target - c++

Question

I am trying to use Neko dlls (written in C++) with the C++ target of Haxe. I am able to call the functions in haxe but not able to pass values.
This is the C++ code -
value Hello(value h)
{
cout << val_int(h);
return val_int(1);
}DEFINE_PRIM(Hello, 1);
This is the Haxe code -
class Main
{
var load = cpp.Lib.loadLazy( "ndll" , "Hello", 1 );
static function main()
{
load(1);
}
}
It executes only if the function does not take parameters. Also, the value that is returned form the C++ function to Haxe is null.
This code actually works perfectly when I compile for the neko target, but it doesn't seem to work with the cpp target.
Any help is appreciated.

Answer 1

Here's the fully corrected C++ code :
#define IMPLEMENT_API
/* Will be compatible with Neko on desktop targets. */
#if defined(HX_WINDOWS) || defined(HX_MACOS) || defined(HX_LINUX)
#define NEKO_COMPATIBLE
#endif
#include <hx/CFFI.h>
#include <stdio.h>
/* Your hello function. */
value hello(value h)
{
printf("%i\n", val_int(h));
return alloc_int(1);
}
DEFINE_PRIM(hello, 1);
/* Main entry point. */
extern "C" void mylib_main()
{
// Initialization code goes here
}
DEFINE_ENTRY_POINT(mylib_main);
What's important is that every value given as an argument to a primitive or returned by a primitive must be of the type value. That's why your parameter and return didn't work.
val_int is used to convert a value into a native C type, so your printing code was correct. But your return was wrong : you can't return a C int type when the function expects you to return a value to Haxe. You need to create a new Haxe Int type and return it. This is done with the help of alloc_int.
Here's the Haxe part of the code as a reference :
class Main
{
static var hello = cpp.Lib.load("myLib", "hello", 1);
static function main()
{
var myReturnedInt:Int = hello(1);
}
}
A few helpful links :
Neko C FFI
Neko FFI tutorial
CPP FFI notes

Answer 2

In order for this to work, you'll have to add to the header of your cpp file:
#define IMPLEMENT_API
#include <hx/CFFI.h>
(instead of neko's headers)
If you want the ndll to run on both neko and hxcpp, you should also add
#define NEKO_COMPATIBLE
before the hx/CFFI.h include.
You can compile using whatever is best for you, but I recommend using a Build.xml to generate your ndll, since it will automatically add the include and lib paths correctly for hxcpp's headers. You can see an example of a very simple Build.xml here:
http://pastebin.com/X9rFraYp
You can see more documentation about hxcpp's CFFI here: http://haxe.org/doc/cpp/ffi