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I have 2 arrays in C# and one API in c++ (provided library, no source)

public struct POS_DATA_2D
{
    public UInt32 u32_opt;
    public Int32 i32_x;
    public Int32 i32_y;
    public Int32 i32_theta;
}
public struct PNT_DATA_2D
{
    public UInt32 u32_opt;
    public Int32 i32_x;
    public Int32 i32_y;
    public Int32 i32_theta;
    public Int32 i32_acc;
    public Int32 i32_dec;
    public Int32 i32_vi; 
    public Int32 i32_vm;
    public Int32 i32_ve;
}
int cnt = 58;
POS_DATA_2D[] pPosarr = new POS_DATA_2D[cnt];
PNT_DATA_2D[] pPntarr = new PNT_DATA_2D[cnt];

The problem is when I call the below API the program crashed. I guessed it accessed array element which isn't correct.

ADCNC_W32.APS168.VelocityPlanning(cnt, ref pPosarr[0], ref pPntarr[0]);

The description of that API

 [DllImport("ADCNC.dll")]public static extern Int32 
VelocityPlanning(
    System.UInt32 PosCount    // [IN ] position array count, [1,4294967295]
 ,  ref POS_DATA_2D PosArray    // [IN ] position array start pointer, [!NULL]
 ,  ref PNT_DATA_2D PntArray    // [OUT] point array start pointer, [!NULL]
 );

Please help me to point out the incorrect points. Thanks!

Improve this question
5
  • possible duplicate of How to marshal an array of structure In C#? Commented Feb 4, 2015 at 16:20
  • Can you post the C method declaration so we can check if the DllImport is written correctly? Commented Feb 4, 2015 at 16:24
  • This is structure in C++ I32 __stdcall VelocityPlanning( U32 PosCount , POS_DATA_2DPosArray, PNT_DATA_2D PntArray ); Commented Feb 4, 2015 at 17:12
  • That C++ doesn't look like it is accepting an array. It looks like it is accepting a single POS_DATA_2D object, passed by value on the stack. But your C# code clearly is passing a pointer to an array element. I can't tell entirely without seeing the definition of POS_DATA_2D in the C++ code. Can you post that too? Also: Make sure you check the structure size and alignment. Commented Feb 5, 2015 at 21:39
  • This is truct of POS_DATA_2D public struct POS_DATA_2D { public UInt32 u32_opt; public Int32 i32_x; public Int32 i32_y; public Int32 i32_theta; } Commented Feb 10, 2015 at 13:15
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