Marching arrays from C # to C ++ and vice versa: PInvokeStackImbalance

Question

I have a C ++ function with which I would like to access from C #. The problem is that I keep getting PInvokeStackImbalance exceptions, and I don't know why. Everything works fine and is expected to verify that the exception is disabled.

Signature of my C ++ function:

extern "C" double solveQP(
    int32_t n, int32_t mE, int32_t mI,
    double *p_G, double *p_g0,
    double *p_CE, double *p_ce0,
    double *p_CI, double *p_ci0,
    double *p_x)

and what I used to access it:

        [DllImport("libQuadProg.dll")]
        [return: MarshalAs(UnmanagedType.R8)]
        private static extern double solveQP(
            [In, MarshalAs(UnmanagedType.I4)] int n,
            [In, MarshalAs(UnmanagedType.I4)] int mE,
            [In, MarshalAs(UnmanagedType.I4)] int mI,
            [In, MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.R8)] double[] p_G,
            [In, MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.R8)] double[] p_g0,
            [In, MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.R8)] double[] p_CE,
            [In, MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.R8)] double[] p_ce0,
            [In, MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.R8)] double[] p_CI,
            [In, MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.R8)] double[] p_ci0,
            [In, MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.R8)] double[] p_x);

I also tried it with the UnmanagedType.LPArray option and nothing at all. I believe there is one detail about PInvoke that I just don't get, and I would appreciate it if someone pointed this out.

Answer 1

DllImport CallingConvention. Cdecl , C __stdcall. [MarshalAs], , , . :

    [DllImport("libQuadProg.dll", CallingConvention = CallingConvention.Cdecl)]
    private static extern double solveQP(
        int n, int mE, int mI,
        double[] p_G,
        // etc...
    }