Marcus' Blog

Marshalling native function pointers

Fri, 06 Apr 2007 09:13:08 GMT

Now that the book is written and all urgent tasks I had to defer due to the book are done, I find some time to blog about technical topics.

Recently, a customer asked me how to marshal function pointers across managed / unmanaged interop boundaries. If you know a simple API and two attributes and if you are aware of a pitfall specific to marshaling function pointers, the job can be quite easy.

To discuss this topic, consider the following simple API:

 namespace NativeAPI

{

  struct CallbackData

  {

    int i;

    double d;

  };



  typedef void (*PFNCallback)(CallbackData* p);



  class SampleClass

  {

    PFNCallback _pfn;

  public:

    SampleClass(PFNCallback pfn);

    void F();

  };

}

In my book I focus on wrapping class libraries that use virtual functions for callbacks instead of function pointers, because virtual functions are the typical C++-like approach for callbacks. But obviously, a lot of C++ class libraries have their roots in C which can force you to care about arguments of function pointer types.

The managed equivalent to a native function pointer is a delegate. There are different ways to map between delegates and function pointers. The following code shows a delegate that can be mapped to the native function pointer of type PFNCallback:

 namespace ManagedWrapper {   using namespace System::Runtime::InteropServices;



  [StructLayout(LayoutKind::Sequential)]

  public value struct CallbackData

  {

    int i;

    double d;

  };



  [UnmanagedFunctionPointer(CallingConvention::Cdecl)]

  public delegate void CallbackDelegate(CallbackData% p);

}

Notice that I first define a managed wrapper type for CallbackData that has the same binary layout as its native counterpart. This is done with the StructLayout attribute. The attribute is only used for documentation purposes, because sequential layout is the default setting for custom value types defined in C++/CLI (and C#). The delegate type has the UnmanagedFunctionPointerAttribute, which is not optional in this case. Using this attribute, you can specify the calling convention of the native function pointer type. In the native API's header file, the PFNCallback is defined without an explicit calling convention specification – this is not recommended, but it occurs quite often. In this case, the function pointer type has the default calling convention, which depends on compiler switches. If no compiler switch is used, the default calling convention for C-style function pointers is __cdecl. Using the compiler switches /Gz or /Gr, the default calling convention can be changed to __stdcall or __fastcall. In the concrete scenario that my customer faced, neither /Gz nor /Gr are used. To express that the CallbackDelegate should be marshaled to a __cdecl function pointer, the UnmanagedFunctionPointerAttribute is necessary. If the native function pointer is a __fastcall function, you can not provide a simple mapping, because calling __fastcall functions from managed code is not supported by the current version (2.0) of the CLR. Once you have properly defined the delegate, you can use the function Marshal::GetFunctionPointerForDelegate to receive a pointer to a native->managed thunk for the delegate. This pointer can then be passed to native code. If native code uses this pointer for function calls, the thunk performs the native->managed transition and invokes the delegate. To wrap NativeAPI::SampleClass, you can implement the following wrapper class:

 namespace ManagedWrapper

{

  public ref class SampleClass

  {

    NativeAPI::SampleClass* _pWrappedObject;

    CallbackDelegate^ _callbackDelegate;

  public:

    SampleClass(CallbackDelegate^ cbd);

    void F();

    ~SampleClass();

  };

}

In the constructor of this wrapper class, you can use Marshal::GetFunctionPointerForDelegate to determine the function pointer that is passed to the constructor of NativeLib::SampleClass. The following code shows the implementation of ManagedWrapper::SampleClass.

 namespace ManagedWrapper

{

  SampleClass::SampleClass(CallbackDelegate^ callbackDelegate)

  : _callbackDelegate(callbackDelegate),

  _pWrappedObject(nullptr)

  {

    IntPtr p = Marshal::GetFunctionPointerForDelegate(_callbackDelegate);

    _pWrappedObject = new NativeAPI::SampleClass((NativeAPI::PFNCallback)p.ToPointer());

    if (!_pWrappedObject)

      throw gcnew OutOfMemoryException("Could not allocate
memory on C++ free store");

  }



  void SampleClass::F()

  {

    _pWrappedObject->F();

  }



  SampleClass::~SampleClass()

  {

    NativeAPI::SampleClass* pWrappedObject = _pWrappedObject;

    _pWrappedObject = nullptr;

    delete _pWrappedObject;

  }

}

Notice that in the member initialization list of the constructor, I first store a handle to the target delegate in a member variable. This is important, to control the lifetime of the thunk. At the first view, one might think that the thunk manages a tracking handle to the target delegate, which would keep the delegate alive as long as the thunk exists. However, the opposite is the case. It is not the thunk that keeps the delegate alive; the delegate keeps the thunk alive: The thunk is guaranteed to exist only as long as the delegate exists. The thunk only contains a weak reference to the target delegate which it can use for invocation if the delegate is not garbage collected. Due to this implementation, the following code would definitely be a bug:

 SampleClass::SampleClass(CallbackDelegate^ callbackDelegate)

: _pWrappedObject(nullptr)

{

  IntPtr p = Marshal::GetFunctionPointerForDelegate(callbackDelegate);

  _pWrappedObject = new NativeAPI::SampleClass((NativeAPI::PFNCallback)p.ToPointer());

  if (!_pWrappedObject)

    throw gcnew OutOfMemoryException("Could not allocate memory
on C++ free store");

}

Since the delegate that was used to create the thunk (and the function pointer referring to the thunk) is not stored in a member variable, it can be GCed unless other references to the delegate exist. When this delegate is GCed, the thunk can be removed as well. Notice that the thunk is not automatically removed when its target delegate is deleted, because the thunk and the delegate are created on different heaps: the delegate is instantiated on the GC heap, whereas the thunk is created on a heap that I like to call the CLR's code heap. An important difference of these heaps is that the code heap consists of memory pages that have the attribute PAGE_EXECUTE_READWRITE. The following code shows you some internals about Marshal::GetDelegateForFunctionPointer

 // GFPFDTests.cpp

// build with "CL /clr GFPFDTests.cpp"



#include "windows.h"



using namespace System;

using namespace System::Diagnostics;

using namespace System::Runtime::InteropServices;



typedef void (__cdecl* PFN)();



[UnmanagedFunctionPointer(CallingConvention::Cdecl)]

public delegate void PFNDelegate();



// managed function has __cdecl calling convention

// therefore, a PFN can point to it.

void __cdecl F()

{

Console::WriteLine("::F called");

}

int main(array ^args)

   {

     PFNDelegate^ d1 = gcnew PFNDelegate(F);

     IntPtr p1 = Marshal::GetFunctionPointerForDelegate(d1);

     IntPtr p2 = Marshal::GetFunctionPointerForDelegate(d1);

     // calling M::GFPFD twice for same delegate returns same thunk

     Debug::Assert(p1 == p2);

   

     PFNDelegate^ d2 = gcnew PFNDelegate(F);

     p2 = Marshal::GetFunctionPointerForDelegate(d2);

     // calling M::GFPFS twice for different delegates returns

     // different thunks even if delegate target is the same

     Debug::Assert(p1 != p2);

     MEMORY_BASIC_INFORMATION mbi;

     VirtualQuery(p1.ToPointer(), &mbi, sizeof(mbi));

     // thunks are allocated on a heap that consits of pages   //
   with the PAGE_EXECUTE_READWRITE flag

     Debug::Assert((mbi.Protect & PAGE_EXECUTE_READWRITE) ==

                    PAGE_EXECUTE_READWRITE);

   

     void* pD1 = *(void**)&d1; // hack to get native pointer to delegate

     VirtualQuery(pD1, &mbi, sizeof(mbi));

     // .NET objects are allocated on the GC heap which consists of

     // pages with the PAGE_READWRITE flag

     Debug::Assert((mbi.Protect & PAGE_READWRITE) ==

                   PAGE_READWRITE);

   

     PFN pfn = (PFN)p1.ToPointer();

     pfn();

     WeakReference wr(d1);

     d1 = nullptr;

     GC::Collect(2);

     Debug::Assert(!wr.IsAlive);

     try

     {

       pfn();

       // since the target delegate does not exist any more,

       // an exception is thrown here and the line below is

       // not executed

       // if you execute this in a debugger, you will likely see

       // a "Managed Debugging Assistant" instead.

       // MDAs are CLR internal assertion-like constructs     Debug::Assert(FALSE);

     }

     catch (System::AccessViolationException^ ex)

     {

       Debug::WriteLine("Expected exception");

     }

   }

In this post I have discussed how to treat marshal delegates to native function pointers. However, I have not discussed what you should do if the signature of the native function requires parameter marshalling. This will be addressed in my next post.

Finishing my book

Sat, 13 Jan 2007 09:00:07 GMT

A long project is comming to an end soon. After one year of writing, my book will be finished soon. 3 chapters need some minor changes. All other chapters of my book are now going to be copy edited. The book will summarize essentail parts of my research on C++/CLI in the last two years. Notice that the announcement in amazon.com is not 100% correct. The title of the book will be "Expert C++/CLI: .NET for Visual C++ programmers" and the release date will be Mid March.

Some personal things

Tue, 11 Apr 2006 12:15:43 GMT

1) Since April, 1st I am an MVP for Visual C++.

2) My first article in the MSDN Magazine has been published: http://msdn.microsoft.com/msdnmag/issues/06/05/MixAndMatch/default.aspx

Mixed mode DLLs: Problem with public functions using native types as arguments

Tue, 21 Mar 2006 17:36:54 GMT

In news://msnews.microsoft.com/microsoft.public.dotnet.languages.vc Edward Diener asked an very interesting question: Why can't I call a function having arguments of a native type like std::string from another assembly?

Assume you have some code like this one:

// Conversions.cpp

// compile with "CL /clr /LD conversions.cpp"

// output: mixed code assembly Conversions.dll

#include <string>

public ref class Conversions
{
public:
static void S2S(System::String^ s1, std::string& s2) { /* ... */ }
};

This code should compile as expected, however, it would not give you the expected result!

The code below looks like a suitable client:

// ConversionsClient.cpp

// compile with "CL /clr ConversionsClient.cpp"

#using "Conversions.dll"

#include <string>

int main()
{
std::string s;
Conversions::S2S("asdf", s);
}

If you try to compile this code, you will get a disappointing error message:

error C3767: 'Conversions::S2S': candidate function(s) not accessible

Why is a public static function S2S of a public type Convesions not accessible?

To use the native type std::string in managed code, the compiler generates a managed value type std::string in the assembly where std::string is used. This managed wrapper value type is private, therefore, the Conversions::S2S cannot be called from outside the assembly even though it is a public function of a public type.

At the first view it seems, key to the solution is to make sure the compiler generates a public type for std::string, in theory this is possible, however it would not help to solve the problem. In fact the native wrapper type has been defined as a private type for some good reasons.

Assume the native wrapper type for std::string was public. To call S2S, one would have to pass a tracking handle to a System::String, defined in mscolib.dll, and a value of the type std::string defined in the assembly Conversions.dll. The std::string type that we pass in ConversionsClient.cpp is a different one! It is the native wrapper type defined in ConversionsClient.cpp - not the native wapper type defined in Conversions.dll. Therefore, the parameters would not match.

So how can we solve this problem?

The origin of the problem is the fact, that type identity rules of .NET do not allways mix well with the type identity rules of native C++. To solve this problem, you can switch back to the world of native code sharing without loosing you managed code features. Simply create a mixed code static library:

Create a static mixed code library from the code :

// ConversionsLib.cpp

// compile with "CL /c /clr ConversionsLib.cpp"

// make lib with "LIB ConversionsLib.obj"

// output: mixed code static library ConversionsLib.lib

#include <string>

void S2S(System::String^ s1, std::string& s2) { /* ... */ }

Create a client from the code below.

// ConversionsLibClient.cpp

// compile with "CL /clr ConversionsLibClient.cpp"

#include <string>

#pragma comment (lib, "ConversionsLib.lib")

void S2S(System::String^ s1, std::string& s2);

int main()
{
std::string s;
S2S("asdff", s);
}

Conclusion: Beware the different type identity rules. Native types are identifies by their namespace-qualified typename, managed types are identified by their assembly- and namespace-qualifies typename. If you need native type identity rules, use native code sharing features, if you need managed type identity, use managed code sharing features.

Reflector Add-In for C++/CLI available

Fri, 20 Jan 2006 11:07:12 GMT

http://www.mybadhairday.com/cppcliinstall.html

Avoid native code in managed object files (".obj" files)

Thu, 12 Jan 2006 15:29:45 GMT

When a cpp file is compiled with /clr, a managed object file is created. In most scenarios, such a managed object file contains only managed code. However, there are two scenarios that end up in a managed object file with managed and native code:

When #pragma unmanaged is used
When the C++ file contains a function with C++ constructs that are not mappable to IL code.

Managed object files with native code imply a certain danger: They can end up in uninitialized state, as shown in the following sample:

In the code below, i is a global variable initialized with the return value of getValue(). There are two exported functions that simply return i. One is the managed function fManaged and the other one is the unmanaged function fUnmanaged.

<code language=”C++/CLI” filename=”MixedLib.cpp” compileWith=”CL /LD /clr MixedLib.cpp”>
#pragma unmanaged
__declspec(noinline) int getValue() {
return 42;
}

int i = getValue();

__declspec(dllexport) int fUnmanaged()
{
return i;
}

#pragma managed
__declspec(dllexport) int fManaged()
{
return i;
}
</code>

Before fManaged is executed the first time, the module constructor is called. The module constructor calls getValue to initialize the global variable i. However, if fUnmanaged is called before fManaged is called the first time, the variable i will be returned before it is initialized. To reproduce this scenario, you can use the client application below.

<code language=”C++/CLI” filename=”TestApp.cpp” compileWith=”CL /clr TestApp.cpp”>
#include <stdio.h>

#pragma comment(lib, "testlib.lib")

__declspec(dllimport) int fUnmanaged();
__declspec(dllimport) int fManaged();

int main()
{
printf("fUnmanaged returns %d\n", fUnmanaged());
printf("fManaged returns %d\n", fManaged());
printf("fUnmanaged returns %d\n", fUnmanaged());
}
</code>

If you start TestApp.exe, you will get the following output:

fUnmanaged returns 0
fManaged returns 42
fUnmanaged returns 42

The easiest way to avoid these problems is to make sure that files compiled with /clr contain only managed code and to leave the native code in cpp files compiled without /clr. If you consider using #pragma unmanaged or unmappable C++ constructs in files compiled with /clr, you should be aware that all global variables and static member variables of that file, are initialized by the module initializer. This is even true if the variable is of a native type.

The compiler's ability to automatically compile a function with unmappable C++ constructs to native code can cause a scenario where you get mixed code object files without even realizing it. Fortunately a compiler warning C4793 can be emitted in this scenario. C4793 is a level 2 warning. To get it, you either have to set the warning level to 2, or you have to use a compiler switch to make it a level 1 warning, as shown in the following code.

When you compile this code, the C++ compiler will emit the warning C4793 with the following message:

UnmappableConstructs.cpp(3) : warning C4793: '__asm' : causes native code generation for function 'void f(void)'
UnmappableConstructs.cpp(1) : see declaration of 'f'

Interesting new feature in .NET: Type identity mapping.

Sat, 26 Nov 2005 11:06:15 GMT

.NET has a very interesting new feature regarding type identity. When I tested this feature the last time (I think it was with the RC, it did not work, so it is likely you have not yet heared about it). But let's start from the beginning:

Type identity is a very important concept of a programming infrastructure. In classic C++, types are identified by their names. COM uses GUIDs to identitfy types. To achieve a strong type safety, type identity in .NET is bound to assembly identity and assembly identity can be bound to developers using a public/private key pair. Type identity is bound to assembly identity means that 2 types with the same name in two different assemblies have two different identities. Assembly identity can be bound to developers using a public/private key pair means that developers can use unique public/private key pairs to give their assemblies unique and uncloneable names. This also gives all types in the assembly unique and uncloneable names.

The following expression returns a string containing the unique and uncloneable type identity, Microsoft has given to the 32 bit signed integer type:

int::typeid->AssemblyQualifiedName

If you are not familiar with the chosen language, the equivalent C# expression would be typeof(int).AssemblyQualifiedName.

While this type identity is very helpful to achieve verifiability, it is also had a drawback: This assembly bound type identity ment that a type could not leave the assembly where it was defined in without losing it's identity. You can define a type from exactly the same code in another assembly, but to the runtime, it would be a different type. To understand this, let's have a look at the following example.

Let's assume you have an assembly lib1.dll created from the following code:

public ref class TheType {};

Let's further assume, you have a client application like this one:

#using "lib1.dll"
int main() {
using namespace System;
Console::WriteLine(TheType().GetType()->AssemblyQualifiedName);

using System::Reflection::Assembly;
for each (Assembly^ a in AppDomain::CurrentDomain->GetAssemblies())
Console::WriteLine(a->FullName);
}

Notice the elegant way to add an assembly reference inside your code, and the neat alternative for creating a temporary object of type TheType - two out of so many reasons why I call C++/CLI the chosen language.

If you run the application, you will see that TheType is defined in Lib1 and that the assemblies mscorlib, app, and lib1 are loaded.

Let's further assume that for the next version, you are redesigning your application and you find out, that TheType would now better fit into another assembly. Due to the type identity rules I have mentioned, this would mean that TheType would get another identity. Therefore this would be a breaking change for lib1.dll: The new version of Lib1 would not be backwards compatible with the old one, since it didn't have the public type TheType any more.

Using the type identity mapping feature in 2.0, you can reorganize your libraries without causing a backwards incompatibility in your new lib1.dll. To explain the mechanics, let's assume the source for lib2.dll now contains TheType:

//lib2.cs
public ref class TheType {};

To allow the old version of app.exe to execute even though TheType is no longer in the assembly where it is expected (lib1), you can define TheType in lib1.dll with a type identity mapping to the type in lib2.dll. These two lines are enough to achieve this:

#using "lib2.dll"
[assembly: TypeForwardedTo(TheType::typeid)];

Notice that this code creates lib1.dll with an assembly depencency to lib2.dll that defines TheType. When using this code, the compiler emits the folowing metadata for TheType in lib1.dll:

.class extern forwarder TheType
{
.assembly extern lib2
.class 0x02000002
}

.class 0x02000002 is to the metadata token for TheType in lib2.dll.

Almost the same metadata can be emitted by C#, too; however there is a slight difference:

[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(TheType))]

C# expects you to use the pseudo custom attribute System::Runtime::CompilerServices::TypeForwardedToAttribute, whereas C++/CLI uses a compiler-internal attriubte TypeForwardedTo. The philosophies of the two languages differ here: C# tries to be consistent in the way attributes are used. Regarding attributes, C++/CLI has different roots anyway: .NET attributes are, attributed ATL are two examples. Instead of trying to be consistent with one or the other attribute model, C++/CLI tries to avoid that the programmer has to explicitly use features of the runtime that are intended to be used by compiler builders only.

Whatever language you use, this simple attribute allows you to reorganize your libraries without breaking compatibility with old applications.

How to use app.config files in Visual C++ 2005 projects

Fri, 11 Nov 2005 23:34:30 GMT

For most Visual Studio .NET language integrations, app.config files are treated specially. Before the target application is started, (with or without a debug session), the language package ensures that the app.config file is automaticallly copied to the target application's configuration file. Visual C++ does not have this feature, however it is easy to get the same:

Add a file named app.coinfig to a Visial C++ project and choose the following project settings:

Command line: type app.config > "$(TargetPath).config"

Description: "Updating target's configuration file"

Outputs: "(TargetPath).config"

Notice that the file is copied via the command type and piping. I prefer this to using the copy command here, sbecause this command ensures that the date of the compiled file is automatically adapted whenever the file is copied.

Can DLLs export managed functions to native clients?

Wed, 19 Oct 2005 21:58:59 GMT

On microsoft.public.dotnet.languages.vc, bonk has asked this interesting question. This blog entry gives you a simple example and explains why this is possible. In further blogs I will discuss when this can be dangerous.

Your idea is possible, but there may be some issues. Let's start with a simple sample

<code language="CPPCLI" file="test.cpp" compileWith="CL /LD /clr test.cpp">
// pragma managed is the default
extern "C" __declspec(dllexport) void __stdcall f()
{
System::Console::WriteLine("I am f(), a managed function that test.dll exports to native clients");
}
</code>

"dumpbin /exports test.dll" will show you that there is indeed a native exported function:

ordinal hint RVA name

1 0 00001020 _f@0

What is going on here? How can unmanaged code can call managed code?

To answer this question, let's have a look at a simple application that calls managed code from unmanaged code:

<code language="CPPCLI" file="testApp.cpp" compileWith="CL /clr testapp.cpp">
void f()
{
System::Console::WriteLine("I am f(), a managed function that can be called by native clients");
}

void f2()
{
System::Console::WriteLine("I am f2(), a managed function that can be called by native clients");
}

#pragma unmanaged
int main() {
f();
f2();
}
</code>

The native function main can not call f without some magic that is going on under the hood: Think of a scenario, where f has not even been jit compiled. On the one hand, the call "f()" is compiled to a call to an address local to the exe file, on the other hand, the code that should really be executed, is JIT compiled. So what is going on here?

"f()" and "f2()" are indeed calls a local addresses. This is an excerpt from the disassembly window:

f();
00401053 call f (401030h)
f2();
00401058 call f2 (401040h)

Notice that the calling addresses (00401053) and the called addresses (401030) are both belong to testApp.exe's code.

Here is what the disassembly window tells us about the called addresses:

f:
00401030 jmp dword ptr [__mep@?f@@$$FYAXXZ (409000h)]

f2:
00401040 jmp dword ptr [__mep@?f2@@$$FYAXXZ (409004h)]

"jmp dword ptr [...x...]" is an indirect jump. It means: at the address ...x..., is the address the address you have to jump to.

Here is what these addresses are in my debugger's memory window:
0x00409000: 00 CB 00 12
0x00409004: 00 CB 00 4E

Both addresses are far away from testApp.exe's base address, so they are clearly outside testApp's code. This is runtime generated code, but we have not yet reached JIT compiled code. What we see here are runtime generated unmanaged -> managed thunks. These thunks perform the managed / unmanaged transition call the managed functions (f, or f2) in the end.

As I have mentioned, these functions are runtime generated: How does the runtime know that at address 0x00409000 should be a pointer to the unmanaged -> managed thunk for f() and at address 0x00409004 should be a pointer to the thunk for f2()?

Well the new linker is much smarter than you may expect: The linker generates .NET metadata that tells the runtime exactly that! If you view testApp.exe in ILDASM and inspect the assembly's manifest, you will find so called vtFixups at the end of the manifest. Here is an expert:

.imagebase 0x00400000
.subsystem 0x0003 // WINDOWS_CUI
.corflags 0x00000000
.vtfixup [1] int32 retainappdomain at D_00009000 // 06000001
.vtfixup [1] int32 retainappdomain at D_00009004 // 06000002
...many other vtfixups elided for clarity here ...

Note that these lines contain familiar numbers: 00009000 and 00009004. If you add the .imagebase to these numbers, you will get:

00409000 and 00409004. Does this ring the bell? Using these addresses, the compiled code finds the managed -> unmanaged thunks.

So what is the other part of the vtfixup 06000001 and 06000002?

Well these are metadata tokens. Metadata starting with the 06 are always method tokens and now it is not very difficult to guess what is going on: 06000001 is the metadata token for the managed function f() and 06000002 is the metatdata token for f2(). You can prove this by adding the following code to f() and f2():

System::Console::WriteLine("{0:x8}", (gcnew System::Diagnostics::StackTrace())->GetFrame(0)->GetMethod()->MetadataToken);

The .vtfixup metadata tells the runtime:
When the assembly is loaded:
Generate a unmanaged->managed thunk for the method f() and store a pointer to it in 00409000 and
generate another unmanaged->managed thunk for method f2() and store a pointer to it in 00409004.

Since this is done, the unmanaged function main can call the managed functions f and f2 as if they were native functions.

In the testApp.exe sample there is a simplification, that is not true for the test.dll I have disused right at the beginning: Since testApp.exe is an exe it is guaranteed that the CLR has been initialized already. (The CLR will be initialized automatically when the EXE application starts.) This assumption is not true for managed functions exported via DLLs: The DLL's client may be a native client. To handle this case, a small stub is exported. This small stub ensures that the CLR is initialized properly and that the assembly is loaded properly into the default appdomain, before the unmanaged -> managed stub is called. This is often called delayed CLR initialization.

Although all this sounds nice there are still some things to discuss:

* Issues when combining exported managed functions with #pragma managed

* Turning the generation of managed / unmanaged thunks off in cases where they are not needed

* What happens if managed code calls a managed entry point via P/Invoke?

I hope I will find some time to discuss these things in the next days.

My Essential C++/CLI Seminar

Wed, 19 Oct 2005 20:39:05 GMT

A long time of research will come to an end soon. I have spent the last months writing the Essential C++/CLI class for DevelopMentor. I still have 8 labs to write and some slides need a redesign, but at least I am able to spend some time sharing important details about C++/CLI, "It Just Works", and .NET in General.