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POC# Calling C++ DLL Function which returns a struct
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  1. POC# Calling C++ DLL Function which returns a struct
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    copied!<p>I have an C++ dll which defines a struct and an dll call like this:</p> <pre><code>typedef const char* FString; typedef struct { FString version; FString build_no; FString build_type; FString build_date; FString build_info; FString comment; } FVersionInfo; extern "C" FAPI_EXPORT FVersionInfo CALLINGCONV fGetVersion(void); </code></pre> <p>On the c# side i using an dynamic loading:</p> <pre><code> [DllImport("kernel32.dll", EntryPoint = "LoadLibrary")] static extern int LoadLibrary( [MarshalAs(UnmanagedType.LPStr)] string lpLibFileName); [DllImport("kernel32.dll", EntryPoint = "GetProcAddress")] static extern IntPtr GetProcAddress(int hModule, [MarshalAs(UnmanagedType.LPStr)] string lpProcName); [DllImport("kernel32.dll", EntryPoint = "FreeLibrary")] static extern bool FreeLibrary(int hModule); [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct FVersionInfo { public string Version; public string Build_No; public string Build_Type; public string Build_Date; public string Build_Info; public string Comment; } [UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Ansi)] public delegate FVersionInfo fGetVersion(); public fGetVersion GetVersion; FHandle = LoadLibrary(@pName); IntPtr intPtr; intPtr = GetProcAddress(FHandle, "fGetVersion"); GetVersion = (fGetVersion)Marshal.GetDelegateForFunctionPointer(intPtr, typeof(fGetVersion)); </code></pre> <p>The calling code should be:</p> <pre><code>FVersionInfo version = new FVersionInfo(); version = GetVersion(); </code></pre> <p>My first problem is, that i become an "System.Runtime.InteropServices.MarshalDirectiveException" on the call of Marshal.GetDelegateForFunctionPointer in the c# loading part. </p> <p>I have then tested using IntPtr as struct return parameter like that:</p> <pre><code>[UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Ansi)] public delegate IntPtr fGetVersion(); </code></pre> <p>So i got the Marshal.GetDelegateForFunctionPointer to work, but later i've got the same problems with marshaling:</p> <pre><code>IntPtr DllValue = new IntPtr(); FVersionInfo version = new FVersionInfo(); DllValue = fGetVersion(); Marshal.PtrToStructure(DllValue, FVersionInfo); </code></pre> <p>Here it crashes at the fGetVersion() call with "Managed Debugging Assistant 'PInvokeStackImbalance'". I think it means, that the stack is corrupted (imbalanced).</p> <p>I have tested with many variants of the structure definition, but no result.</p> <p>Any ideas or suggestions would be welcome!</p>
 

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