Marshalling problem (from managed to unmanaged)

[s196675m]

HOPEFULLY someone can help me. I am trying to access a function from an unmanaged DLL from my visual c++ managed GUI. Declaration of the function I am trying to import from unmanaged (native) DLL is: extern "C" __declspec(dllexport) TGrayImage* init_seg(TGrayImage* pImg, TMonoImage* monoImg, int nClass) Even though there are many functons in the DLL, only this function is exported. Now In my GUI, I have added the following line to import that functon so that I can call that functon from GUI. At the top of the file after using namespaces [System::Runtime::InteropServices::DllImport("segment.dll")] TGrayImage * init_seg(TGrayImage* pimg, TMonoImage* mono, int nNum); I didn't do any Marshalling parameter. I have no idea how to Marshall a pointer to a Template class or pointer to a class. I searched before posting but I didn't get clear understanding about it. Just for clarification, pimg and mono I am trying to pass is Managed varialble created within managed GUI. TGrayImage* pimg = new TGrayImage* (width,height);// used new not gcnew TmonoImage* mono = new TMonoImage(width, height); I have added the proper library (compiled with pure:MSIL) in my my GUI which supplied TGrayImage,TMonoImage. Header file for TGrayImage and TMonoImage already included in the GUI. When I call init_seg function from GUI, I got the following message: An unhandled exception of type 'System.AccessViolationException' occurred in GUI.exe Additional information: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. Please help me to Marshall these parameter correctway. I will appreciate your big help. Thank you.

[led mike]

I can't decipher your post.

s196675m wrote:

I am trying to access a function from an unmanaged DLL from my visual c++ managed GUI. Declaration of the function I am trying to import from unmanaged (native) DLL is: extern "C" __declspec(dllexport) TGrayImage* init_seg(TGrayImage* pImg, TMonoImage* monoImg, int nClass)

First you indicate an unmanged source, then:

s196675m wrote:

Just for clarification, pimg and mono I am trying to pass is Managed varialble created within managed GUI. TGrayImage* pimg = new TGrayImage* (width,height);// used new not gcnew TmonoImage* mono = new TMonoImage(width, height); I have added the proper library (compiled with pure:MSIL) in my my GUI which supplied TGrayImage,TMonoImage.

At this point I am at a complete loss to understand your scenario.

led mike

[s196675m]

Sorry, for ambiguity.

led mike wrote:

s196675m wrote: I am trying to access a function from an unmanaged DLL from my visual c++ managed GUI. Declaration of the function I am trying to import from unmanaged (native) DLL is: extern "C" __declspec(dllexport) TGrayImage* init_seg(TGrayImage* pImg, TMonoImage* monoImg, int nClass) First you indicate an unmanged source, then:

Yes you are right. This line of declaration from unmanged source. (part of unmanaged DLL.

led mike wrote:

s196675m wrote: Just for clarification, pimg and mono I am trying to pass is Managed varialble created within managed GUI. TGrayImage* pimg = new TGrayImage* (width,height);// used new not gcnew TmonoImage* mono = new TMonoImage(width, height); These sample code is part of GUI( managed). I just showed here how I initialize pimg and mono variables before passing to the imported function I have added the proper library (compiled with pure:MSIL) in my my GUI which supplied TGrayImage,TMonoImage. Here I am trying to mean, The other library I used with GUI also complied as a managed library. At this point I am at a complete loss to understand your scenario.

Now my main question is: (1) Did I imported the function correctly ? (2) Do I need to marshall the parameters before passing to the function? (3) How Can I marshall the first two parameters? Thank you.

[Mark Salsbery]

The passed pointers should marshal no problem. Where exactly is the exception occurring?  Can you step into the init_seg() call in the debugger? Mark

Mark Salsbery Microsoft MVP - Visual C++ :java:

[led mike]

s196675m wrote:

Now my main question is:

Sorry but have not at all cleared up the seeming contradictory statements in your orginal post

s196675m wrote:

I have added the proper library (compiled with pure:MSIL) in my my GUI which supplied TGrayImage,TMonoImage. Here I am trying to mean, The other library I used with GUI also complied as a managed library.

First you say it's a native library then you seem to be saying you compiled it as a managed library (pure:MSIL). It can't be both so I still have no idea what you are saying.

led mike

[uusheikh]

I think the easiest way is to use #pragma unmanaged/managed. Set your project properties to /clr, create a native function and wrap it with #pragma unmanaged/managed, include your .h native library header and link to your .lib. Call the native function from your GUI.

[Mark Salsbery]

Maybe, but I tried code like the OP's and it works fine.  Until (s)he answers with better error info, it's hard to tell, but I think the error has nothing to do with marshaling. Mark

Mark Salsbery Microsoft MVP - Visual C++ :java:

[led mike]

Mark Salsbery wrote:

but I think the error has nothing to do with marshaling.

It's far more likely it's due to copy/paste coding rather than actually understanding the technologies you are attempting to utilize. By the way, what the heck were you doing being on here 7 hours ago? Get some sleep ;P

led mike

[Mark Salsbery]

Agreed.

led mike wrote:

By the way, what the heck were you doing being on here 7 hours ago?

Hehe it's hectic around here.  My GF is working long hours here on graduation projects for her second degree. So I just hang out getting some work done or playing on CP...until the screenwriters start cranking out new TV show episodes again ;P  I work at home so regular work hours just don't exist.

Mark Salsbery Microsoft MVP - Visual C++ :java: