Managed C++/CLI

Execute managed function from unmanaged

26-Dec-06 21:57

Thanks, I yust needed that.

yoti1126-Dec-06 0:02

yoti11

26-Dec-06 0:02

Hello,
I’m trying to send delegate to unmanaged code, so when the unmanaged class will catch an event it will execute the proper function in the managed class.
I used GCHandle::Alloc() to prevent from the GC to change the position on the heap and
Marshel::GetFunctionPointerForDelegate()to convert the delegate to unmanaged function pointer.
The main problem is that an error occurred while I tries to execute the function pointer in the unmanage code to the managed code I get that error.
“
Managed Debugging Assistant 'FatalExecutionEngineError' has detected a problem in 'D:\Dev\Test_TA.exe'.
Additional Information: The runtime has encountered a fatal error. The address of the error was at 0x79f1c189, on thread 0x910. The error code is 0xc0000005. This error may be a bug in the CLR or in the unsafe or non-verifiable portions of user code. Common sources of this bug include user marshaling errors for COM-interop or PInvoke, which may corrupt the stack.
“

Did anyone encounter this problem?
Is it a problem with the Marshel::GetFunctionPointerForDelegate()? Or with the GC?

Thanks,

http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1034501&SiteID=1[^]

567890123426-Dec-06 2:08

5678901234

26-Dec-06 2:08

yoti1126-Dec-06 3:08

yoti11

26-Dec-06 3:08

Hi,
Thanks for your reply.
I already try that before, but it my case the program structure is little different.
The problem is that the program has 2 phases:
1. Managed class creates a delegate and sends it to unmanaged class which assigns it to a function pointer member.
2. The unmanaged class listens to events from other place and when a specific event occurred then the unmanaged class should call the function in the managed class.
(From the first phase)

Maybe there is no different between cases but I still get this error.

Thank you,

567890123426-Dec-06 3:25

5678901234

26-Dec-06 3:25

This is almost same case. The only difference that EnumWindows calls managed callback number of times inside of method, and keeping local delegate instance is enough. In your case you need to keep delegate as class member.
I think the problem is in function prototype. What is required unmanaged prototype and managed callback prototype?

In my program I use another method for managed callback - because I didn't know about this Marshal function when started to write it. Code fragments:

GCHandle gcHandle; // managed class member

// Constructor:
gcHandle = GCHandle::Alloc(this);
void* callbackPtr = GCHandle::ToIntPtr(gcHandle).ToPointer();
pUnmanagedClass->SetCallbackAddress(callbackPtr);

// Destructor:
gcHandle.Free();

Pass callbackPtr value to unmanaged class. This is simple unmanaged void* pointer, which allows to call managed class function when necessary.

// Unmanaged class calls managed class:
GCHandle h = GCHandle::FromIntPtr(IntPtr(callbackPtr)); // callbackPtr is passed from managed class
YourManagedClass^ pThis = (YourManagedClass^)h.Target;
pThis->CallbackFunction();

calling String ^ * from C#

yoti1126-Dec-06 6:21

yoti11

26-Dec-06 6:21

I still get the error

Managed Debugging Assistant 'FatalExecutionEngineError' has detected a problem in 'D:\Dev\Test_TA.exe'.
Additional Information: The runtime has encountered a fatal error. The address of the error was at 0x79f1c189, on thread 0x910. The error code is 0xc0000005. This error may be a bug in the CLR or in the unsafe or non-verifiable portions of user code. Common sources of this bug include user marshaling errors for COM-interop or PInvoke, which may corrupt the stack.

This error ocured when the function pointer in the unmanaged code call
to the function in the managed code.
In the managed code I uesd GCHandle::Aloc(this).

thanks

ByStorm Software25-Dec-06 17:09

25-Dec-06 17:09

I'm sure that this is a stupid question and that I am just missing some obvious but here it goes.

I'm adding a remoting interface to an MFC service that I have. I've gotten it to compile and run with the CLI and now I'm porting the COM interface to a remoting interface.

Then I hit a problem.

I have some methods that return values as parameters..you know the old "BOOL *" and the ever popular "LPTSTR *"....anyway... in C++/CLI these get translated to Boolean * and String^ *.

the problem is...HOW in the world do I call these from C#? I know it's a reference, but c++/cli doesn't support the keyword REF and c# doesn't like things like "&".

I guess I could try to jump thru a lot of hoops and get it to work via unmanaged code, but this SEEMS like a simple syntax problem.

sorry again to bother people with this, but for the life of me...I can't find the "right" keywords to get google to show me what I need.

thanks,

Gene

bsaksida26-Dec-06 19:47

26-Dec-06 19:47

Do you want to call String from c# to MFC or to c++/cli

If you chose c++/cli, yust add a project to your solution, and add a reference.

ByStorm Software27-Dec-06 4:27

27-Dec-06 4:27

What I'm trying to do is call the C++/cli from C#. The method I'm calling is trying to return an out parameter like String^ *. It would be a "ref" in c# and a & in normal C++.

I did figure it out though. the magic symbol is %. it looks like % means ref in C++/CLI.

bsaksida27-Dec-06 4:35

27-Dec-06 4:35

Let's say you have a class in C#.

And both project are under your solution.

Go to c++/cli project setting, and add a reference by projects, and select a project c#.

When in c++/cli:

using namespace projectCSharNamespace;
projectCSharpClass ^cl = gcnew projectCSharpClass();
cl->String.

But why do you want as String^ *, instead yust String^

ByStorm Software27-Dec-06 4:42

27-Dec-06 4:42

the C++/CLI function will be returning a value in the string passed in.

sort of like in c#
void GetName(ref string nameStr)
{
nameStr = "sam";
}

in c++ it would be

void GetName(string^ * nameStr)
{
*nameStr = "sam";
}

The problem happened when I tried to call c++ from c# since c# doesn't understand * unless it's unsafe.

bsaksida27-Dec-06 5:40

27-Dec-06 5:40

As i coud see with docmetation, (Nothing at all) And my test, i coud see that it isn't possible to do as reference. Why don't you use as return. If you wan't a multiple variables, you coud use struct.

This coud be a bug, missing features or left out Intentionaly.

ByStorm Software27-Dec-06 6:12

27-Dec-06 6:12

I figured it out. if you want to pass variables around as reference in C++/CLI you have to mark them with a %.

so instead of
void GetName(String ^ * name)
{
*name = "sam";
}

you do this:
void GetName(String^% name)
{
name = "Sam";
}

then you call it from c# like this:
String nameStr;
GetName(ref nameStr);

handling system call result in C

RockyMu1-Jul-22 15:01

RockyMu

1-Jul-22 15:01

Thanks ByStorm. You saved my life. Been searching for this for weeks.

xface6625-Dec-06 8:08

xface66

25-Dec-06 8:08

hi all,

i am writing a C programin Linux.
i want to make a system call and assign its result in to a variable.
how can i do this?

thanks in advance

xface6625-Dec-06 8:52

xface66

25-Dec-06 8:52

i have found the answer myself and writing it down here;
popen() function did the work for me Smile | :)

Library: stdio.h

Prototype: FILE *popen(const char *command, const char *type);

Syntax: FILE *fp;
fp = popen( "ls -l", "r");

Notes:
command - is the command to be issued.
type - r - read O/P from command.
- w - Write data as I/P to command.

Christian Graus25-Dec-06 10:41

Christian Graus

25-Dec-06 10:41

I'm glad you found your answer. If you have more questions, please ask in the right forum, this one is for managed C++ only.

Christian Graus - C++ MVP

'Why don't we jump on a fad that hasn't already been widely discredited ?' - Dilbert

xface6625-Dec-06 12:36

xface66

25-Dec-06 12:36

which forum could i ask that question? i havent seen a forum about C.

John R. Shaw26-Dec-06 1:03

John R. Shaw

26-Dec-06 1:03

He means the "Visual C++ / MFC" forum, because it is a more general forum.

INTP
"Program testing can be used to show the presence of bugs, but never to show their absence."Edsger Dijkstra