String conversion in c++/CLI - Managed C++/CLI Discussion Boards

Cyrilix3-Oct-08 13:00

3-Oct-08 13:00

I think I might've found the issue. I believe it lies with trying to reference an unmanaged lib (not compiled with managed extensions in C++), from a project that is compiled into a managed executable (managed extensions enabled). From what I've read, it seems to me (so far) that the only way to do this is to use a .dll and PInvoke, but is there any way to simply use a .lib?

Re: Program too big to fit in memory

Mark Salsbery3-Oct-08 14:49

Mark Salsbery

3-Oct-08 14:49

The lib should work fine. C++/CLI lets you call code in static and
dynamic libraries without p/invoke.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Program too big to fit in memory

Cyrilix3-Oct-08 21:44

Cyrilix

3-Oct-08 21:44

Hi Mark,

Thanks for the info, however, here's the problem. The first time I do a build, it always fails with a LNK1000 error where essentially, VC7's link.exe throws some kind of exception. If I try to build it again, it succeeds. Always. The only problem is, that the generated executable is invalid. At first, I couldn't figure out what was wrong. Then, because I suspected some kind of dependency issue, I ran depends.exe on the generated executable, and it told me that the PE header was invalid (or something to that effect). Then, that was where I suspected the managed/unmanaged stuff.

I should also note that I have a solution of 3 projects, 1 of which is the executable (managed), 1 of which is a static library (managed), 1 of which is a static library (unmanaged). If I remove the unmanaged static library from its reference list or dependency chain, building the executable complains about linker errors (as expected, since I have not defined the symbols). As soon as I add the unmanaged static library, I get the LNK1000.

Re: Program too big to fit in memory

Mark Salsbery4-Oct-08 7:13

Mark Salsbery

4-Oct-08 7:13

Cyrilix wrote:
1 of which is a static library (managed)

I'm not sure how well that's going to work, nor can I find any
solid confirmation one way or the other.

Binding of managed types in a library is done at the assembly level.
I'm not sure how well the linker's going to handle that.

A managed class library (DLL) is the appropriate way to make a managed
library (even if it has native code in it as well).

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Program too big to fit in memory

Cyrilix4-Oct-08 8:45

Cyrilix

4-Oct-08 8:45

Well, the way it works is that I have a managed static lib that contains my __gc classes. Then, I have an unmanaged static lib depending on and using the managed static lib that contains regular (non __gc) classes, which is sort of my interface to the native world. I've been able to use this interface with other classes from native code without problem. Then, I have a Winforms app which depends on that native interface. Now that I think of this, it doesn't really make sense as to why I'm doing it this way. I'm sort of going Managed->Unmanaged->Managed... might as well see if I can cut out the middle layer.

Re: Program too big to fit in memory

Mark Salsbery4-Oct-08 7:24

Mark Salsbery

4-Oct-08 7:24

Cyrilix wrote:
I'm compiling in Visual Studio 2003

I definitely recommend moving to at least VS 2005 (VC 8) any way you can,
as soon as you can, before investing a lot of time in code that is incompatible
with newer/future C++ compilers.

With VC8+, you get the actual C++/CLI language instead of the Managed Extensions
you are using with VC7, which aren't supported anymore (there's a compiler switch
to allow it...for now).

The Managed Extensions for C++ syntax is deprecated.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Program too big to fit in memory

Cyrilix4-Oct-08 8:46

Cyrilix

4-Oct-08 8:46

I am pushing for this as well, but I'm not sure if I'll be able to convince them to allocate hours to upgrade our entire system before I finish this small project. Also, I think the Managed C++ in VC8+ definitely also looks much nicer in terms of syntax.

String conversion in c++/CLI

Robin Imrie1-Oct-08 4:05

Robin Imrie

1-Oct-08 4:05

Hi,

I am porting my vc2003 app to vc2008 and have come across somthing like this...

// this defined
LPCTSTR lpsz = _T("myString");

// then later
// where Afunc is defined as
// SomeObject* AFunc( String *str );
SomeObject *obj = Afunc( lpsz );

under vc2003 this compiles and works file however in vc2008 it seems that i need to do...

// this defined
LPCTSTR lpsz = _T("myString");

// then later
// where Afunc is defined as
// SomeObject^ Afunc( String ^str );
SomeObject ^obj = Afunc( gcnew String(lpsz) );

the documentation on string literals in C++/CLI migration primer suggest that the following could be done.

SomeObject ^obj = AFunc( safe_cast<string^>(lpsz) );

this is wrong as it not compile.

I not sure the gcnew string( lpsz ) method is ideal. is there a better way or what is the propper way of doing this.

thanks

Robin

Re: String conversion in c++/CLI

led mike1-Oct-08 4:36

led mike

1-Oct-08 4:36

Robin Imrie wrote:
I not sure the gcnew string( lpsz ) method is ideal. is there a better way or what is the propper way of doing this.

in general gcnew is how you create managed objects in C++/CLI so that is always a correct way to do it. Of course strings can be different like in Native C++ based on what you need them for. In your code you are creating a native string and then converting it to a managed string.

If you only need a managed string then you could do this.

System::String^ lpsz = "myString";

There is a series of introductory C++/CLI articles here on CodeProject. I suggest you take advantage of them.

led mike

Re: String conversion in c++/CLI

Robin Imrie1-Oct-08 4:45

Robin Imrie

1-Oct-08 4:45

Thanks mike for that i had suspected as much.

Will give the C++/CLI articles a good look.

gtk installation

SeshaSridhar1-Oct-08 1:00

SeshaSridhar

1-Oct-08 1:00

Hi all,

We installed gtk from the following site
http://crossfire.real-time.com/clients/win32_gtk.html
please help us how to compile and run our own c++ files

Thank You
Sesha Sridhar

Error while calling VC# function in VC++

Andy Rama29-Sep-08 0:36

Andy Rama

29-Sep-08 0:36

Hi to all,

I have an 'Windows Form Control Library' "VideoWindow.dll" in VC#.Net 2008, having code as following,

<block><br />
    using DirectShowLib;//C# DirectShow Library<br />
<br />
<br />
    public partial class VideoWindow : UserControl<br />
    {<br />
        public VideoWindow()<br />
        {<br />
            InitializeComponent();<br />
        }<br />
<br />
        Label m_picVideoWindow = new Label();<br />
<br />
        public int SetPreview(IVideoWindow vwRenderer)<br />
        {<br />
            int hr = 0;<br />
            if (m_picVideoWindow.Bounds.IsEmpty)<br />
                return hr;<br />
            try<br />
            {<br />
                hr = vwRenderer.put_WindowStyle(WindowStyle.Child | WindowStyle.ClipChildren | WindowStyle.ClipSiblings);<br />
                DsError.ThrowExceptionForHR(hr);<br />
                hr = vwRenderer.put_Owner(m_picVideoWindow.Handle);<br />
                DsError.ThrowExceptionForHR(hr);<br />
                hr = vwRenderer.SetWindowPosition(0, 0, m_picVideoWindow.Width, m_picVideoWindow.Height);<br />
                DsError.ThrowExceptionForHR(hr);<br />
                hr = vwRenderer.put_Visible(OABool.True);<br />
                DsError.ThrowExceptionForHR(hr);<br />
            }<br />
            catch (Exception ex)<br />
            {<br />
            }<br />
            return hr;<br />
        }<br />
    }<br />
</block>

When I am calling SetPreview() from my VC++.Net 2008 MFC Application as follows,

<block><br />
IVideoWindow	*pWidnow;//C++ DirectShow Library<br />
CWinFormsControl<VideoWindow::VideoWindow> *a1 = new CWinFormsControl<VideoWindow::VideoWindow>();<br />
<br />
(*a1)->SetPreview(pWidnow);<br />
</block>

It gives compile error as,
error C2664: 'VideoWindow::VideoWindow::SetPreview' : cannot convert parameter 1 from 'IVideoWindow *' to 'DirectShowLib::IVideoWindow ^'

Please help me to solve this error.

Regards,
Aniket A. Salunkhe

Re: Error while calling VC# function in VC++

led mike29-Sep-08 4:31

led mike

29-Sep-08 4:31

Aniket Salunkhe wrote:
Please help me to solve this error.

Well a Native C++ pointer

Aniket Salunkhe wrote:
IVideoWindow *pWidnow;

Is not going to be convertible to a managed object.

Aniket Salunkhe wrote:
DirectShowLib::IVideoWindow ^

If you don't know that, then you need to do some studying of C++/CLI basics and fundamentals. There is a series of CLI beginner articles here on Code Project.

led mike

Re: Error while calling VC# function in VC++

Mark Salsbery29-Sep-08 7:27

Mark Salsbery

29-Sep-08 7:27

Aniket Salunkhe wrote:
When I am calling SetPreview() from my VC++.Net 2008 MFC Application as follows,

IVideoWindow *pWidnow;//C++ DirectShow Library
CWinFormsControl<videowindow::videowindow xmlns:videowindow="#unknown"> *a1 = new CWinFormsControl<videowindow::videowindow>();

Handles to managed objects use ^, not * in C++.
Also you use gcnew, not new, to allocate them on the managed heap.

Aniket Salunkhe wrote:
(*a1)->SetPreview(pWidnow);

Huh?

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Error while calling VC# function in VC++

George L. Jackson1-Oct-08 3:21

George L. Jackson

1-Oct-08 3:21

Mark, FYI, Aniket Salunkhe is trying to call managed code from native C++ according to this quote: "When I (Aniket Salunkhe) am calling SetPreview() from my VC++.Net 2008 MFC Application ...".

"We make a living by what we get, we make a life by what we give." --Winston Churchill

Re: Error while calling VC# function in VC++

Mark Salsbery1-Oct-08 4:51

Mark Salsbery

1-Oct-08 4:51

That was pretty obvious from the error message as well Smile | :)

I only commented about the syntax/language use.
I suppose I could have mentioned that (s)he'll have to
compile with /CLR.

Cheers,
Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Error while calling VC# function in VC++

Andy Rama3-Oct-08 19:16

Andy Rama

3-Oct-08 19:16

Mark Salsbery wrote:
he'll have to
compile with /CLR.

I am already using this flag (/CLR).

Re: Error while calling VC# function in VC++

Mark Salsbery4-Oct-08 6:42

Mark Salsbery

4-Oct-08 6:42

I knew that from the error message.

You're using the wrong syntax for managed objects.
The error message is fairly clear.

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Re: Error while calling VC# function in VC++ [modified]

George L. Jackson1-Oct-08 7:14

George L. Jackson

1-Oct-08 7:14

The C++ DirectShow Library's IVideoWindow and C#'s DirectShowLib::IVideoWindow^ are not the same interface (at least externally). SetPreview is looking for C#'s IVideoWindow; thus, you may need to use COM callable wrapper (CCW) of your DirectShowLib::IVideoWindow^.

"We make a living by what we get, we make a life by what we give." --Winston Churchill

modified on Wednesday, October 1, 2008 2:05 PM

Re: Error while calling VC# function in VC++

Andy Rama3-Oct-08 19:28

Andy Rama

3-Oct-08 19:28

George L. Jackson wrote:
you may need to use COM callable wrapper (CCW) of your DirectShowLib::IVideoWindow^.

What is that?

COM object in .net whose threading model is STA, not both

Shao Voon Wong28-Sep-08 23:39

Shao Voon Wong

28-Sep-08 23:39

I have a question regarding STA/MTA in .net

I need to build a COM object in .net whose threading model is required to be STA only (not Both,..) because it is not safe to be used in MTA apartment.
How to do it?

Thank you very much!

Why does Debug::Print prints in the release build version? [modified]

Shao Voon Wong28-Sep-08 15:29

Shao Voon Wong

28-Sep-08 15:29

I have some code which use Debug::Print() to output some debug strings. I notice it also prints in the release build version. IIRC, this is not the case in C#.

Folks, any explanation for this anormaly?

Thank you very much!

Edited: I am using Visual Studio 2005. Looks like I got to use a #ifdef guard to prevent the Debug::Print from printing in the release build.

modified on Sunday, September 28, 2008 9:57 PM

Re: Why does Debug::Print prints in the release build version?

George L. Jackson29-Sep-08 5:50

George L. Jackson

29-Sep-08 5:50

Just for the record, the MSDN Library says (http://msdn.microsoft.com/en-us/library/system.diagnostics.debug.aspx[^]):

"ConditionalAttribute is not supported by the C++ compiler. To provide equivalent functionality, you must enclose calls to the methods of Debug in an #if defined(DEBUG) ... #endif block, and add the /DDEBUG option to the compiler command line or add #define DEBUG to the file."

"We make a living by what we get, we make a life by what we give." --Winston Churchill

How to avoid loading an already loaded shared library

Yashusid25-Sep-08 18:53

Yashusid

25-Sep-08 18:53

Hi,

I have one JNI shared libray which depends on a CPP library.

In my module loading CPP shared library first and loading JNI library, eventhough the dependant library is loaded JNI library tries to load CPP shared library.

Please let me know how to avoid loading an already loaded shared library ....

Thanks,
Yashu

Re: How to avoid loading an already loaded shared library

led mike26-Sep-08 4:37

led mike

26-Sep-08 4:37

Yashusid wrote:
I have one JNI shared libray

As in Java Native Interface? If so this is not even close to being the correct forum. If not then what is it? Supply a link.

In terms of loading modules into Windows Processes put all the modules in a single location. The loader will see that it is already loaded and not load it again.

link[^]

Note Use extreme care when using this value. If LoadLibrary or LoadLibraryEx is called for the same DLL after the DLL is loaded, then the DLL references will not have been resolved. This is because the second call to LoadLibrary or LoadLibraryEx simply returns a handle to the already loaded DLL. In this case, the process is likely to terminate abnormally.

led mike

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.