Managed C++/CLI

6-Nov-03 13:00

Hello All,

I trying to call an unmanged code function from managed code and the unmanaged code function requires a type of WCHAR. How can I convert a __GC String to type of WCHAR so it be passed to the function. If I type out the value, such as const WCHAR *pdn = L"Some value"; It works; however I need the "Some value" to be passed in as a variable. By the way this unmanged code is in unicode, if that helps. Thanks, DC

Tom Archer6-Nov-03 17:29

Tom Archer

6-Nov-03 17:29

<font color=green>// From Extending MFC Applications with the .NET Framework</font>

#include <vcclr.h>
//...
String* s = S"Hello";
const __wchar_t __pin * str = PtrToStringChars(s);

Cheers,
Tom Archer
* Inside C# -Second Edition
* Visual C++.NET Bible
* Extending MFC Applications with the .NET Framework

DR Clevenger7-Nov-03 2:59

7-Nov-03 2:59

Thanks,

When I try this I get the following:
cannot convert parameter 1 from 'const wchar_t __pin *volatile ' to 'WCHAR *' Conversion loses qualifiers: Here is the code

Unmanaged Code
UserStatus* WaitForChanges(WCHAR* dn)
{

UserStatus* status = new UserStatus();
MonitorLDAPChanges(pdn);
return status;
}

Managed Code
const __wchar_t __pin * str = PtrToStringChars(dn);
WaitForChanges(str);

DR Clevenger7-Nov-03 3:20

7-Nov-03 3:20

I got it I forgot to put the 'const' in the method.

Tom Archer7-Nov-03 3:50

Tom Archer

7-Nov-03 3:50

DR Clevenger wrote:
I got it I forgot to put the 'const' in the method

Yep Smile | :)

Here's the thing.

The __pin keyword is used to indicate that the value should not be moved in memory. This is done because a .NET String is subject to being moved about by the GC and when you convert that data into a WCHAR* for purposes of using that pointer over any length of time, you need to ensure that the data is not moved. The WCHAR* is also defined as const because String objects are immutable.

Anyway, you probably know this, but I wanted to give you a complete answer on what is going on here just in case.

Cheers,
Tom Archer
* Inside C# -Second Edition
* Visual C++.NET Bible
* Extending MFC Applications with the .NET Framework

DR Clevenger7-Nov-03 5:27

Error loading C++.Net dll on networkdrv

7-Nov-03 5:27

Thanks for your help and the information.

String question

Ereinion6-Nov-03 11:24

Ereinion

6-Nov-03 11:24

If I have a bit of code like this:
String *s;
int x = 5; y = 10;
Now I want s = "x = (value of x), y = (value of y)"
How do you do that? I hope I explained correctly. I want to be able to change the value of x or y without changing more code.

Re: String question

George L. Jackson20-Nov-03 7:38

George L. Jackson

20-Nov-03 7:38

int x = 5;
int y = 10;
String* s = String::Format(
     S"x = {0}, y = {1}", __box(x), __box(y));

michaelschmitt3-Nov-03 0:40

michaelschmitt

3-Nov-03 0:40

Hi everybody,

i'll try to explain my problem as short as possible:

->My C++ Dll (Native) should be able to call a C# DLL.

Therefore i implemented a managed C++ dll as a bridge( to
avoid COM).
So, the C++(nat) calls the c++(.net) dll, which calls the c# dll.

When the program is started on a local drive, everything
works perfectly, but once it is copied to a network drive
and run form there, loading the "bridge" - dll fails.
In detail : The C++ 6.0 dll uses LoadLibrary to load
the managed C++ dll and immedeately exits with Error 1114 "
Dll initialization failed" - but ONLY started from a network drive.

( calling other dll's works ). I already tried to make a static
link, same error... only on a network drive...
I don't even have to call a function for getting the error..

I'm trying to find the mistake for a long time... but i think
i'm at the end of my wisdom...

Has anybody some kind of an idea, why
calling my C++.Net dll only works on a local drive???
Problem with the dll- entry-point?

Looking forward to some help! Thanks in advance!

Michael

J. Dunlap3-Nov-03 8:45

J. Dunlap

3-Nov-03 8:45

It's because of security restrictions, no doubt.

"Blessed are the peacemakers, for they shall be called sons of God." - Jesus

"You must be the change you wish to see in the world." - Mahatma Gandhi

Michael_Sch3-Nov-03 10:04

Michael_Sch

3-Nov-03 10:04

Hi!

But which restrictions? I do have w/r rights for that drv.

In addition, my .exe has already successfully called 1 other dll (which is native c++ (fortunately Smile | :)

) before calling the c++ managed dll.

Meanwhile, I used the MS Dependeny walker. The profile results
seem to show that there is a problem even when the program
is started from a local drive ( by the way: which u don't notice
without any tool, because it runs correctly )

Profile: ( static link this time )

caloader.exe = my exe
cabridge = my c++ managed.dll

Started "CALOADER.EXE" (process 0x6E8) at address 0x00400000.
Loaded "NTDLL.DLL" at address 0x77F40000.
.
.
.
Loaded "CABRIDGE.DLL" at address 0x10000000.
Loaded "MSCOREE.DLL" at address 0x79170000.
DllMain(0x78000000, DLL_PROCESS_ATTACH, 0x00000000) in "RPCRT4.DLL" called.
DllMain(0x78000000, DLL_PROCESS_ATTACH, 0x00000000)
.
.
.

Entrypoint reached. All implicit modules have been loaded.
DllMain(0x10000000, DLL_PROCESS_ATTACH, 0x0012FD30) in "CABRIDGE.DLL" called.
Loaded "MSCORWKS.DLL" at address 0x791B0000.
Loaded "MSVCR70.DLL" at address 0x7C000000.
Loaded "FUSION.DLL" at address 0x79040000.
.
.
.

Loaded "MSCORLIB.DLL" at address 0x79780000.
Loaded "MSCORLIB.DLL" at address 0x79960000.
DllMain(0x10000000, DLL_PROCESS_ATTACH, 0x0012FD30) in "CABRIDGE.DLL" returned 1 (0x1).
DllMain(0x77E40000, DLL_THREAD_ATTACH, 0x00000000) in "KERNEL32.DLL" called.
DllMain(0x77E40000, DLL_THREAD_ATTACH, 0x00000000) in "KERNEL32.DLL" returned 1 (0x1).
DllMain(0x77DA0000, DLL_THREAD_ATTACH, 0x00000000) in "ADVAPI32.DLL" called.
DllMain(0x77DA0000, DLL_THREAD_ATTACH, 0x00000000) in "ADVAPI32.DLL" returned 14679041 (0xDFFC01).
DllMain(0x78000000, DLL_THREAD_ATTACH, 0x00000000) in "RPCRT4.DLL" called.
.
.
First chance exception 0x80000003 (Breakpoint) occurred in "MSCOREE.DLL" at address 0x79172064.
First chance exception 0xC0000005 (Access Violation) occurred in "CABRIDGE.DLL" at address 0x10000005.
Second chance exception 0xC0000005 (Access Violation) occurred in "CABRIDGE.DLL" at address 0x10000005.
Exited "CALOADER.EXE" (process 0x6E8) with code 128 (0x80).

If you did read until here, thanks Smile | :)

here's my dll:

#include "stdafx.h"
#include "cabridge.h"
#include "windows.h"
extern "C"
{
#include <string.h>
}

#using "mycsharp.dll"

using namespace System;
using namespace mycsharp;

BOOL WINAPI DllMain (HMODULE hModule, DWORD x, LPVOID <)
{
return TRUE;
}

extern "C"
{
__declspec (dllexport) void __cdecl CallCobolAssistBridge(char *pszFileName, int icode, int hwndoutput)
{

String __gc *managed_input = new String(pszFileName);

mycsharp __gc *Mycsharp;
Mycsharp = new mycsharp;

Mycsharp ->DOStuff(managed_input,icode, hwndoutput);

return;
}
}

i hope this wasnt to much..
tanks,
byebye

Michael_Sch3-Nov-03 10:07

Michael_Sch

3-Nov-03 10:07

sorry, please ignore

extern "C"
{
#include
}

was a copy / paste err

thanks for your help!