Develop Reference

How to fix 'Cannot marshal 'return value': Invalid managed/unmanaged type combination (Int/UInt must be paired with SysInt or SysUInt).'

I'm trying to return a struct from a C++ callback from C# and I get the error as described in the title.
I appreciate there is a lot of information, but I wanted to include too much rather than not enough.
I've tried returning the function as a structure, but then read it may be easier to return the function as an IntPtr and use Marshal.PtrtoStructure.
The function that I want to call is from a .dll that comes from a different source and the input is:
C++:
rVDACQ_Connect(int, tVDACQ_CallBackProc, void*, short*, int)
the function in the sample (C++) code returns a struct (rACQ_CallBackRec) which is as follows:
rACQ_CallBackRec = theApp.m_Intf.rVDACQ_Connect(cVDACQ_FBright, CALLBACK_Acquisition, this, m_FrmBuffer, 0);
//rACQ_CallBackRec is the struct type tVDACQ_CallBackRec (as described below)
With CALLBACK_Aquisition being:
extern "C" {
__declspec(dllexport) void _stdcall CALLBACK_Acquisition(tVDACQ_CallBackRec* AR)
{
tVDACQ_CallBackProc test;
((CPreviewDlg*)AR->rUserParam)->My_ACQ_CallBack(AR, test);
}
}
The layout of the struct is as follows:
typedef struct {
int rFlags, // combination of cVDACQ_Fxxxx
rType, // cVDACQ_ETxxx
rEvent, // cVDACQ_Exxx
rSocket; // 0:no relation to a 'socket'; otherwise socket's ID>0 (event's source ID)
TCHAR rMsg[256]; // message (trace, wrn, err)
int rFrameWidth, // full frame width
rFrameHeight; // full frame height
short* rFrameBuffer; // user supplied frame buffer "AFrameBuffer"
union {
int rCaptureRows; // # of received rows (for single frame acquisition)
int rCaptureFrames; // # of received full frames (for framegrabber)
};
int rCapturePercent; // received data in percents
void* rUserCallBackProc, // user supplied "ACallBackProc"
* rUserParam; // user supplied "AUserParam"
int rAborted; // 1: VDACQ_Abort -1:internally
void* rPacketData; // pointer to received packet; usually it is nil
int rFGControl; // frame-grabber's control flags
} tVDACQ_CallBackRec;
typedef void(_stdcall* tVDACQ_CallBackProc)(tVDACQ_CallBackRec*); //The Callback
C#
I've created the callback procedure in C#, as well as the struct and PInvoke:
[UnmanagedFunctionPointer(CallingConvention.StdCall)]
public delegate void tVDACQ_CallBackProc(tVDACQ_CallBackRec AR);
[DllImport("C:\\Users\\jch\\source\\repos\\FlatPanelSensor\\x64\\Debug\\VADAV_AcqS.dll", EntryPoint = "CALLBACK_Acquisition", CallingConvention = CallingConvention.Cdecl)]
public unsafe static extern void CALLBACK_Acquisition(tVDACQ_CallBackRec AR);
[DllImport("C:\\Users\\jch\\source\\repos\\FlatPanelSensor\\FlatPanelSensor\\bin\\Debug\\VADAV_FGM_64.dll", EntryPoint = "VDACQ_Connect", CallingConvention = CallingConvention.Cdecl)]
[return: MarshalAs(UnmanagedType.I4)]
public unsafe static extern IntPtr VDACQ_Connect(int i, [MarshalAs(UnmanagedType.FunctionPtr)] tVDACQ_CallBackProc proc, dynamic n, IntPtr[] buffer, int j);
Struct:
[StructLayout(LayoutKind.Sequential)]
public struct tVDACQ_CallBackRec
{
public int rFlags;
public int rType;
public int rEvent;
public int rSocket;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]
public string rMsg;
public int rFrameWidth;
public int rFrameHeight;
public IntPtr rFrameBuffer;
public int rCaptureRows;
public int rCaptureFrames;
public int rCapturePercent;
public IntPtr rUserCallBackProc;
public IntPtr rUserParam;
public int rAborted;
public IntPtr rPacketData;
public int rFGControl;
}
CallBack:
tVDACQ_CallBackProc callBack =
(AR) =>
{
CALLBACK_Acquisition(AR); //Don't know how necessary this
is
};
Function call:
IntPtr work = VDACQ_Connect(0, callBack, this, m_FrmBuffer, 0);
//I know 'this' isn't defined as a void* in my DLLImport,
//but making it an IntPtr didn't work either so
//the only type I could think of was dynamic.
If I could return this as a IntPtr or, even better, the struct I defined in my C# code that would be great.
If you need anymore information then please let me know, as I think I included everything.

Passing a C++ Array to C# Layer through Net Core

I have a native library and what I'm trying to do is to write a .NET Core wrapper to this native library.
On the native side i have an event called OnSpeechEnded :
virtual void OnSpeechEnded(SpeechEndInfo seInfo) = 0;
and native struct SpeechEndInfo has the following structure:
struct SpeechEndInfo
{
std::vector<AudioData> UntouchedData;
std::vector<AudioData> AudioAfterPostSpeechUntilSilenceTrigger;
};
Corresponding .NET Standard Class:
public struct SpeechEndedInfo
{
public SpeechEndedInfo(short[] untouchedData, short[] audioAfterPostSpeechUntilSilenceTrigger)
{
UntouchedData = new short[untouchedData.Length];
untouchedData.CopyTo(UntouchedData, 0);
AudioAfterPostSpeechUntilSilenceTrigger = new short[audioAfterPostSpeechUntilSilenceTrigger.Length];
audioAfterPostSpeechUntilSilenceTrigger.CopyTo(AudioAfterPostSpeechUntilSilenceTrigger, 0);
}
public short[] UntouchedData { get; set; }
public short[] AudioAfterPostSpeechUntilSilenceTrigger { get; set; }
};
On .NET Standard side, the following delegate is defined:
delegate void OnSpeechEndedInter(
[In, MarshalAs(UnmanagedType.LPArray)] short[] untouched,
int untouchedSize,
[In, MarshalAs(UnmanagedType.LPArray)] short[] audioAfterPostSpeechUntilSilenceTrigger,
int audioAfterPostSpeechUntilSilenceTriggerSize);
Declaring pinvoke:
[DllImport("VadLite.Pinvokable.dll", CallingConvention = CallingConvention.Cdecl)]
private static extern void RegisterToSpeechEndedEvent(IntPtr parameters, [MarshalAs(UnmanagedType.FunctionPtr)]OnSpeechEndedInter onSpeechEndedInter);
Declaring _onSpeechEndedInter:
private OnSpeechEndedInter _onSpeechEndedInter;
Assigning a method to the event:
_onSpeechEndedInter = invokedMethod;
...
void invokedMethod(short[] untouchedData,
int untouchedSize,
short[] audioAfterPostSpeechUntilSilenceTrigger,
int audioAfterPostSpeechUntilSilenceTriggerSize)
{
OnSpeechEnded?.Invoke(new SpeechEndedInfo(untouchedData, audioAfterPostSpeechUntilSilenceTrigger));
}
Finally, the code where native arrays are sent:
RegisterToSpeechEndedEvent(
void * possiblyOperations,
void __stdcall onSpeechEndedListener(const int16_t* pUntouchedData, int pUntouchedDataSize, const int16_t *vAudioAfterPostSpeechUntilSilenceTrigger, int vAudioAfterPostSpeechUntilSilenceTriggerSize))
{
auto op = (OperationParameters *)possiblyOperations;
op->OnSpeechEnded([onSpeechEndedListener](SpeechEndInfo ssInfo) {
std::vector<int16_t> untouchedData;
std::vector<int16_t> audioAfterPostSpeechUntilSilenceTrigger;
for (auto & audioData : ssInfo.UntouchedData)
{
untouchedData.insert(untouchedData.end(), audioData.Samples, audioData.Samples + audioData.SampleCount);
}
for (auto & audioData : ssInfo.AudioAfterPostSpeechUntilSilenceTrigger)
{
audioAfterPostSpeechUntilSilenceTrigger.insert(audioAfterPostSpeechUntilSilenceTrigger.end(), audioData.Samples, audioData.Samples + audioData.SampleCount);
}
onSpeechEndedListener(untouchedData.empty() ? nullptr : untouchedData.data(),
(int)untouchedData.size(),
audioAfterPostSpeechUntilSilenceTrigger.empty() ? nullptr : audioAfterPostSpeechUntilSilenceTrigger.data(),
(int)audioAfterPostSpeechUntilSilenceTrigger.size());
});
After running the test program and getting meaningful array sizes on the native side, C# arrays UntouchedData and AudioAfterPostSpeechUntilSilenceTrigger always seem to have size 1.
Probably there is a detail I have missed. I can provide further detail if it is required. Thanks.

Great!, Finally I have found out the problem. In the delegate declaration, I just had to introduce parameter SizeParamIndex :
delegate void OnSpeechEndedInter(
[In, MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] short[] untouched,
int untouchedSize,
[In, MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] short[] audioAfterPostSpeechUntilSilenceTrigger,
int audioAfterPostSpeechUntilSilenceTriggerSize);
Because the marshaler cannot determine the size of an unmanaged array, we have to pass it in as a separate parameter considering the signature of the method and zero based indexing.

How to assign value to a char array (C-String) within C++ DLL through C# code

I have a DLL developed in C++ that performs some computations. I am trying to link this DLL into my C# application.
I have a struct within a struct which contains a char array (C string). I have a pointer to the object created by the C++ DLL within my C# application.
namespace Test
[StructLayout(LayoutKind.Sequential)]
public unsafe struct Child
{
public float number1;
public float number2;
[MarshalAs(UnmanagedType.LPArray)]
public char[] name;
}
[StructLayout(LayoutKind.Sequential)]
public unsafe struct DataStructure
{
public Child child;
...
}
.
.
.
public unsafe partial class Form1:Form {
[DllImport("Calculation.dll", CallingConvention = CallingConvention.Cdecl)]
unsafe public static extern IntPtr createInstance();
[DllImport("Calculation.dll", CallingConvention = CallingConvention.Cdecl)]
unsafe public static extern DataStructure* processData(IntPtr source); // Setup of data
[DllImport("Calculation.dll", CallingConvention = CallingConvention.Cdecl)]
unsafe public static extern int calculate(IntPtr calc); // Perform calculation
.
.
public Form2()
{
private void button1_Click_1(object sender, EventArgs e)
{
// test functions
unsafe
{
IntPtr ptr1 = createInstance(); // Returns pointer to the instance
DataStructure* data = processData(ptr1); // Returns pointer to DataStructure object created through DllImport
data->child.number1 = 1.234F; // Works
data->child.number1 = 9.876F; // Works
data->child.name = "......" // This doesn't work!!
int result = calculate(ptr1); // Returns value when name commented
}
}
}
}
If I don't comment name, I get the Error - Cannot take the address of managed object.
If I comment name, I am able to run the calculation without issue.
I wish to update the value of the char array name but can't seem to figure out the solution. Below is my usual C solution. Thanks!
#include "DataStructure.h"
#define DLLNAME "Calculation.dll"
int main(int argc, char** argv) {
HINSTANCE dllHandle = LoadLibraryA(fileNameDll);
const void* ptr1 = 0;
int result = 0;
DataStructure *data;
ptr1 = createInstance();
data = processData(ptr1);
data->child.number1 = 1.234;
data->child.number2 = 9.876;
sprintf(data->child.name, "3104-03");
result = calculate(ptr1);
}

How to convert c++ QString parameter to c# string

I'm trying to hook the QPainter::drawText function in another application by injecting my DLL and detour the QPainter::drawText function to my own application. I'm doing this because the other application does not expose a usable API and I want to do some basic statistical analysis on the data I'm getting.
All is working fine: I see the QPainter::drawText functions being called, but I'm unable to convert the QString parameter to anything useful. All I get is two characters when I Marshall the QString parameter as LPWStr.
I'm no C++ superhero, so I'm a bit lost. I think I'm looking at some pointer or reference because of the two characters I get for each call, but I'm not sure. After a few nights trying to make sense of it I'm close to the point of giving up.
I've demangled the QPainter::drawText function (found using Dependency Walker: ?drawText#QPainter##QAEXABVQRect##HABVQString##PAV2##Z) with https://demangler.com/ and it comes up with this function declaration:
public: void __thiscall QPainter::drawText(class QRect const &,int,class QString const &,class QRect *)
I've converted this into the following DllImport (I substituted the QRect and Qstring classes to IntPtr, because I have no idea how to convert them to C#).
[DllImport("Qt5Gui.dll", SetLastError = true, CharSet = CharSet.Unicode, CallingConvention = CallingConvention.ThisCall, EntryPoint = "?drawText#QPainter##QAEXABVQRect##HABVQString##PAV2##Z")]
public static extern void QPainter_drawText(IntPtr obj, IntPtr p1, int p2, IntPtr p3, IntPtr p4);
This is what I have so far:
Detouring Qt QPainter::drawText
LocalHook QPainter_drawTextHook;
[DllImport("Qt5Gui.dll", SetLastError = true, CharSet = CharSet.Unicode, CallingConvention = CallingConvention.ThisCall, EntryPoint = "?drawText#QPainter##QAEXABVQRect##HABVQString##PAV2##Z")]
public static extern void QPainter_drawText(IntPtr obj, IntPtr p1, int p2, IntPtr p3, IntPtr p4);
[UnmanagedFunctionPointer(CallingConvention.ThisCall, CharSet = CharSet.Unicode, SetLastError = true)]
delegate void TQPainter_drawText(IntPtr obj, IntPtr p1, int p2, IntPtr p3, IntPtr p4);
static void QPainter_drawText_Hooked(IntPtr obj, IntPtr p1, int p2, IntPtr p3, IntPtr p4)
{
var qs3 = (QString)Marshal.PtrToStructure(p3, typeof(QString));
try
{
((Main)HookRuntimeInfo.Callback).Interface.GotQPainter_drawText(qs3.ToString());
QPainter_drawText(obj, p1, p2, p3, p4);
}
catch (Exception ex)
{
((Main)HookRuntimeInfo.Callback).Interface.ErrorHandler(ex);
}
}
Create QPainter::drawText detour
QPainter_drawTextHook = LocalHook.Create(
LocalHook.GetProcAddress("Qt5Gui.dll", "?drawText#QPainter##QAEXABVQRect##HABVQString##PAV2##Z"),
new TQPainter_drawText(QPainter_drawText_Hooked),
this);
QPainter_drawTextHook.ThreadACL.SetExclusiveACL(new Int32[] { 0 });
Update 2016-1-31
Thus far I have found this (see https://github.com/mono/cxxi/blob/master/examples/qt/src/QString.cs). But now I'm getting an AccessViolationException on the Marshal.PtrToStringUni.
[StructLayout(LayoutKind.Sequential)]
public unsafe struct QString
{
[StructLayout(LayoutKind.Sequential)]
public struct Data
{
public int #ref;
public int alloc, size;
public IntPtr data;
public ushort clean;
public ushort simpletext;
public ushort righttoleft;
public ushort asciiCache;
public ushort capacity;
public ushort reserved;
public IntPtr array;
}
public Data* d;
#endregion
public override string ToString()
{
try
{
return Marshal.PtrToStringUni(d->array, d->alloc * 2);
}
catch (Exception ex)
{
return ex.Message;
}
}
}

QString is the complex type.
You can try to import QString::FromUtf16 for create QString and pass IntPtr to your function
string str = "Test";
var p2 = new IntPtr(QString.Utf16(str,str.Length));
EDIT: Also, you can try https://github.com/ddobrev/QtSharp for this

Thanks to the helpful article https://woboq.com/blog/qstringliteral.html, which explains the QString data structure in Qt5 I've managed to get the hook working:
[StructLayout(LayoutKind.Sequential)]
public unsafe struct QString
{
[StructLayout(LayoutKind.Sequential)]
public struct QStringData
{
public int #ref;
public int size;
public uint alloc;
public uint capacityReserved;
public fixed byte data[128];
}
public QStringData* data;
public override string ToString()
{
try
{
var bytes = new byte[data->size * 2];
Marshal.Copy((IntPtr)data->data, bytes, 0, data->size * 2);
return Encoding.Unicode.GetString(bytes);
}
catch (Exception ex)
{
return ex.Message;
}
}
}

Unmarshalling a Struct containing an array of structs

I'm trying to get back this struct from a native C library through P/Invoke:
struct ndb_mgm_cluster_state
{
int no_of_nodes;
struct ndb_mgm_node_state node_states[1];
};
where ndb_mgm_node_state is:
struct ndb_mgm_node_state {
int node_id;
enum ndb_mgm_node_type node_type;
enum ndb_mgm_node_status node_status;
int start_phase;
int dynamic_id;
int node_group;
int version;
int connect_count;
char connect_address[sizeof("000.000.000.000")+1 ];
int mysql_version;
};
The method's signature is:
ndb_mgm_cluster_state* WINAPI wrap_ndb_mgm_get_status(HANDLE handle);
All of this is provided by a 3rd party library, so nothing can be changed.
In C# i have the follow definitions:
[DllImport("Ndb_CWrapper.dll", CharSet = CharSet.Ansi)]
private static extern IntPtr wrap_ndb_mgm_get_status(IntPtr handle);
the structures are:
[StructLayoutAttribute(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct ndb_mgm_cluster_state {
public int no_of_nodes;
public IntPtr node_states;
};
[StructLayoutAttribute(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct ndb_mgm_node_state
{
public int node_id;
public ndb_mgm_node_type node_type;
public ndb_mgm_node_status node_status;
public int start_phase;
public int dynamic_id;
public int node_group;
public int version;
public int connect_count;
[MarshalAsAttribute(UnmanagedType.ByValTStr, SizeConst = 17)]
public string connect_address;
public int mysql_version;
};
I tried to unmarshal the results without success (i recieve an oddly error (not an Exception) Fatal error execution, can be a CLR bug or a miscall P/invoke.
Obviously the reason is a problem in my P/Invoke call
I tried in this way:
First of all i unmarshalled the ndb_mgm_cluster_state structure:
var res=(ndb_mgm_cluster_state)Marshal.PtrToStructure(
tmpPtr, typeof(ndb_mgm_cluster_state));
where IntPtr is the result of the native call.
Up to this step everything "seems" to be done right, but when i try to unmarshall the node_states i get the error:
ndb_mgm_node_state tmpNode = (ndb_mgm_node_state)Marshal.PtrToStructure(
status.node_states, typeof(ndb_mgm_node_state));
What can be the problem? I supposed is something related to the strange declaration of ndb_mgm_cluster_state because is defined an array of 1 element, but it contain several elements. (the number of elements is in no_of_nodes)
WORKAROUND:
The only way to let everything work i found is to change a bit the signature, in this way:
ndb_mgm_node_state* WINAPI wrap_ndb_mgm_get_status(HANDLE handle,int* length);
in C#:
[DllImport("Ndb_CWrapper.dll", CharSet = CharSet.Ansi)]
private static extern IntPtr wrap_ndb_mgm_get_status(IntPtr handle,out int length);
where length contains no_of_nodes
the unmarshall will be in this way:
IntPtr tmpPtr = wrap_ndb_mgm_get_status(raw,out length);
ndb_mgm_cluster_state tmpRes = new ndb_mgm_cluster_state();
tmpRes.no_of_nodes = length;
tmpRes.node_states = new ndb_mgm_node_state[length];
int step=0;
for (int i = 0; i < tmpRes.no_of_nodes; i++)
{
tmpRes.node_states[i] = (ndb_mgm_node_state)Marshal.PtrToStructure(
tmpPtr+(step*i), typeof(ndb_mgm_node_state));
step = Marshal.SizeOf(tmpRes.node_states[i]);
}
I know the step calculation is odd at the monent, but its not that the point.
there is no way to let the thing work returning directly the ndb_mgm_cluster_state struct instead of do all of this?