Managed C++/CLI

16-Jul-12 23:32

Try fgetc()[^] or ifstream[^].

C++/CLI - Pin a function pointer

krishter10-Jul-12 23:16

krishter

10-Jul-12 23:16

I need to pass a managed callback to an unmanaged TCP receiver. Since its a thread that needs to exist for the lifetime of the application, I need to prevent it from getting garbage collected. I have read everywhere that pinning function pointers is not required and the GCHandle.Alloc will do the job of preventing garbage collection.

But is this a given? I have seen that the AppPool hosting this code crashes with an access violation. Why should I not suspect the fact that this error occurs because the function pointer was garbage collected?

Why does pinning the pointer as below reduce the number of crashes?

C++

typedef void (__cdecl *ProcMessageFunc)(void* param, void* paramBuf, ULONG bufSize);
FuncDelegate^ fp = gcnew MessageFuncDelegate(this, &Handler);
pin_ptr<MessageFuncDelegate^> pinnedFunctionPointer = &fp;
ret = Receiver ((ProcMessageFunc)pinnedFunctionPointer);

Re: C++/CLI - Pin a function pointer

Paul Michalik14-Jul-12 23:51

Paul Michalik

14-Jul-12 23:51

Difficult to say from what you have shown. You can pin a handle to a managed object only temporarily, since a pin_ptr can only be created on the stack. Therefore, if you have something like this:

C++

IntPtr YourClass::GetFuncPointer()
{
    FuncDelegate^ fp = gcnew MessageFuncDelegate(this, &Handler);
    pin_ptr<MessageFuncDelegate^> pinnedFunctionPointer = &fp;
    return ((ProcMessageFunc)pinnedFunctionPointer);
}

then you effectively have only pinned fp for the duration of this method call. A correct way to do this depends on your scenario. I'd recommend something along the lines of the following (I didn't compile it, but you get the idea):

C++

public ref class ClientRegistrar abstract sealed {
    static FuncDelegate^ s_ManagedReceiverList;
    
    // ...
    public static void RegisterClient(YourClient^ p_Client)
    {
        // thread safety for free
        s_ManagedReceiverList += 
            gcnew MessageFuncDelegate(p_Client, &YourClient::Handler);

        // here I assume that ::Receiver is an unmanaged global function which
        // takes a funtion pointer of type ProcMessageFunc. Don't know
        // if you need to deal with multiple registrations....
        ::Receiever((ProcMessageFunc)Marshal::GetFunctionPointerForDelegate(s_ManagedReceiver));
    }

    public static void UnregisterClient(YourClient^ p_Client)
    {
        s_ManagedReceiverList -=
            gcnew  MessageFuncDelegate(p_Client, &YourClient::Handler);
        // use the same schema to unregister from the native receiver
    }
}

Usage (C#):

YourClient tClient = new YourClient();
// ...
ClientRegistrar.RegisterClient(tClient);
// ...

s_ManagedReceiverList and any YourClient instance you register via RegisterClient will be kept alive as long as the current application domain will exist. Implement UnregisterClient if you need more fine grained control. A delegate does not need to be pinned, the CLR takes care of proper handling of that. It just needs to be kept alive.

Cheers,

Paul

modified 17-Jul-12 10:14am.

How to Make and Use Resource DialogBoxes in VC++ 2008

ICEFLOWER226-Jun-12 4:07

ICEFLOWER2

26-Jun-12 4:07

Hi, there

Please give me vc++ learn pdf document or web address or explain about make and use resource dialogbox in vc++ Sniff | :^)

thank you so much Rose | [Rose]

Re: How to Make and Use Resource DialogBoxes in VC++ 2008

Richard MacCutchan26-Jun-12 4:31

26-Jun-12 4:31

See here[^] for DIALOGEX resource statements, and here[^] for programming guides.

Re: How to Make and Use Resource DialogBoxes in VC++ 2008

ICEFLOWER226-Jun-12 7:53

ICEFLOWER2

26-Jun-12 7:53

Please Leave A Sample Source code project if possible with description I'm new comer for VC++ Confused | :confused:

Thank you for your reply Smile | :)

Re: How to Make and Use Resource DialogBoxes in VC++ 2008

Richard MacCutchan26-Jun-12 8:24

26-Jun-12 8:24

Sorry but you will have to find your own. If you are using Visual Studio or Visual C++ Express[^] to create your projects you can use the template in the new project wizard to generate a Dialog project and work from there. You can also find lots of samples in the Articles[^] section.

Getting MdiParent Instance From MdiChild - Windows Forms Application

Paramu197312-Jun-12 1:50

Re: Getting MdiParent Instance From MdiChild - Windows Forms Application

12-Jun-12 1:50

Hi, Iam using VC++ 2010. While I want to get the MdiParent-Forms Instance, its giving the error, Really I can't identify my mistake...

My Codes from MdiParent
=======================

C++

#include "For_Student_Detials"
 
private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
For_Student_Detials^ MyStudentDet= For_Student_Detials::GetForm(true,this);
MyStudentDet->MdiParent=this;
MyStudentDet->FormBorderStyle=System::Windows::Forms::FormBorderStyle::None;
MyStudentDet->Dock=DockStyle::Fill;
MyStudentDet->Show();
}

My Codes From MdiChild // CFIS_Main is my Mdi-Container
=========================================================

C++

#any Include Reqd?????
 
public: static For_Student_Details^ For_Student_Details::_instance = nullptr;
public: static For_Student_Details^ For_Student_Details::GetForm(bool^ IsMDIChild, CFIS_Main^ MyInstFrm) {
if (_instance == nullptr)
    _instance = gcnew For_Student_Details();
 
if (_instance->IsDisposed)
    _instance = gcnew For_Student_Details();
		
if (IsMDIChild)
    _instance->MdiParent = MyInstFrm;
		
return _instance;
}

From the above code I can't identify my mistake, Does anybody can point me?
Thanks For Helps Thumbs Up | :thumbsup:

Richard MacCutchan12-Jun-12 2:15

12-Jun-12 2:15

Paramu1973 wrote:
While I want to get the MdiParent-Forms Instance, its giving the error

What error?

Re: Getting MdiParent Instance From MdiChild - Windows Forms Application

Paramu197312-Jun-12 2:30

Re: Getting MdiParent Instance From MdiChild - Windows Forms Application

12-Jun-12 2:30

Thanks Richard...Thanks for the helps...

Error()
error C2061: syntax error : identifier 'CFIS_Main'
error C2065: 'MyInstFrm' : undeclared identifier
error C2660: 'MyProjectName::For_Student_Details::GetForm' : function does not take 2 arguments

Thumbs Up | :thumbsup:

modified 12-Jun-12 8:54am.

Richard MacCutchan12-Jun-12 3:03

12-Jun-12 3:03

And you expect us to guess how this relates to your project? Please collect information properly, and show the actual lines of code and messages together, ensuring that you identify which line of code is marked with which error.

You could also look more closely at these messages and work out for yourself:

why the identifier 'CFIS_Main' is not recognised.
why you are using the variable 'MyInstFrm', when it has not been defined in the current compilation unit.
why the call to 'MyProjectName::For_Student_Details::GetForm()' has the wrong number of arguments.

Re: Getting MdiParent Instance From MdiChild - Windows Forms Application

Paramu197315-Jun-12 1:30

How to convert from 'WCHAR' to 'System::String ^' Managed C++

15-Jun-12 1:30

Thanks Richard...Manythings I learned from you... Thumbs Up | :thumbsup:

Still all are in mind....I won't forget you & Dave, etc..etc...

Thanks Again Cool | :cool:

ptr_Electron7-Jun-12 20:08

ptr_Electron

7-Jun-12 20:08

How to convert from 'WCHAR' to 'System::String ^' Managed C++

Re: How to convert from 'WCHAR' to 'System::String ^' Managed C++

Richard MacCutchan7-Jun-12 21:58

7-Jun-12 21:58

Use one of the constructors as described here[^].

int x = (Int32) thisisObjectType is boxing, if the type is already checked ?

ptr_Electron7-Jun-12 18:15

ptr_Electron

7-Jun-12 18:15

int x = (Int32) thisisObjectType is boxing, if the type is already checked ?

C++

if (thisisObjectType->GetType() == Int32::typeid) // declaration of thisisObjectType would be…   Object^ thisisObjectType
{
int x = (Int32) thisisObjectType; // will this be considered as boxing ? should this be replaced with TryParse ?
}

Re: int x = (Int32) thisisObjectType is boxing, if the type is already checked ?

Richard MacCutchan8-Jun-12 0:34

8-Jun-12 0:34

Why would you use TryParse() if it's already an integer, and why would you need a cast?

VS2010 Error()- Method or Property 'VCFilter::get_Url Behavior' deprecated and nolonger implemented

Paramu19736-Jun-12 23:57