OpenEuphoria

One issue with this is that he wants to pass a double. Euphoria callbacks can't handle doubles being natively passed. They can only take 31-bit integers (or Euphoria Atoms or Sequences).

The desired signature is:

Public Declare Function MyFunction Lib "c:\MyDLLs\MyDLL.dll" _  
  (ByVal a As Double, ByVal b As Double) As Double  

If you translate (I did this on Linux, but should be similar), you should get some thing like :

$ euc -makefile-full -dll vb.e 
 
// inside vb.c: 
int _1MyFunction(int _a_144, int _b_145) 
{ 
    int _c_146 = 0; 
    int _0, _1, _2; 
     
 
    /** 	atom c = a * b*/ 
    if (IS_ATOM_INT(_a_144) && IS_ATOM_INT(_b_145)) { 
        if (_a_144 == (short)_a_144 && _b_145 <= INT15 && _b_145 >= -INT15) 
        _c_146 = _a_144 * _b_145; 
        else 
        _c_146 = NewDouble(_a_144 * (double)_b_145); 
    } 
    else { 
        if (IS_ATOM_INT(_a_144)) { 
            _c_146 = NewDouble((double)_a_144 * DBL_PTR(_b_145)->dbl); 
        } 
        else { 
            if (IS_ATOM_INT(_b_145)) { 
                _c_146 = NewDouble(DBL_PTR(_a_144)->dbl * (double)_b_145); 
            } 
            else 
            _c_146 = NewDouble(DBL_PTR(_a_144)->dbl * DBL_PTR(_b_145)->dbl); 
        } 
    } 
 
    /** 	return c*/ 
    DeRef(_a_144); 
    DeRef(_b_145); 
    return _c_146; 
    ; 
} 

The easiest thing to do here is probably to write a wrapper function right below the above code:

double MyFunctionDbl( double ad, double bd ){ 
	object a, b, c; 
	double cd; 
	 
	a = NewDouble( ad ); 
	b = NewDouble( bd ); 
	 
	c = _1MyFunction( a, b ); 
	cd = DBL_PTR( c )->dbl; 
	DeRefDS( a ); 
	DeRefDS( b ); 
	DeRefDS( c ); 
	printf("MyFunctionDbl ad %f  bd %f cd %f\n", ad, bd, cd ); 
	return cd; 
} 

And then call that. I wrote this test program to use it:

include std/dll.e 
 
constant 
	VB = open_dll( "/home/matt/eu/test/vb.so" ), 
	MYFUNC = define_c_func( VB, "MyFunctionDbl", {C_DOUBLE, C_DOUBLE}, C_DOUBLE ) 
 
? c_func( MYFUNC, { 0.5, 0.25 }) 
? c_func( MYFUNC, {1, 1 })