Why don’t metaobjects marshal by reference?

Objects that derive from MarshalByRefObject will marshal by reference rather than value. Metaobjects like Assembly, Type and MethodInfo do not derive from MarshalByRefObject. This is because we don’t want Type to be marshal by ref, which implies that none of the metaobjects should. The CLR actually supports a few marshaling styles that aren’t generally available….


Surprising ‘protected’ behavior

There’s a subtle but important difference between protected access in unmanaged C++ and protected access (i.e. family) in the CLR. The difference is due to the CLR’s ability to build security guarantees on top of type safety. Imagine you had a bifurcated hierarchy: Class A { protected M } /                     \ Class G : A         Class X : A There is no relationship between X and G, except…


What is SEHException?

One way you get this exception is if unmanaged code does an OS RaiseException() or causes a fault.  If that exception is propagated up the stack to managed code, we will try to map it to a managed exception.  For example, STATUS_NO_MEMORY maps to OutOfMemoryException and STATUS_ACCESS_VIOLATION maps to NullReferenceException.   For all the exception codes that don’t have a predefined…


Size of a managed object

We don’t expose the managed size of objects because we want to reserve the ability to change the way we lay these things out. For example, on some systems we might align and pack differently. For this to happen, you need to specify tdAutoLayout for the layout mask of your ValueType or Class. If you…


DLL exports

People often ask how they can expose traditional DLL exports from managed assemblies. Managed C++ makes it very easy to export functions. And you could use tricks like ILDASM / ILASM to inject DLL exports into managed assemblies built with other languages like C#. However, there is a fundamental mismatch between the process-wide notion of…


Hyper threading

If the operating system schedules multiple threads against a hyper-threaded CPU, the CLR automatically takes advantage of this. This is certainly the case for new versions of the OS like Windows Server 2003. Also, the CLR did work to properly spin on a hyper threaded system. If you are writing your own spinlocks in managed…


Turning off the garbage collector

It is not generally possible to turn off garbage collection. However, the garbage collector won’t run unless “provoked.” Garbage collection is triggered by: Allocation Explicit calls by the application to System.GC.Collect Explicit calls by the application to services that implicitly trigger a GC. For example, unloading an AppDomain will trigger at least one full GC….


Error C0020001

#define BOOTUP_EXCEPTION_COMPLUS 0xC0020001 You may see an exception with this code, or an HRESULT of this value, when trying to call into managed code. This can happen if you call in before the runtime has finished initializing, or after the runtime has started shutting down. Sometimes it’s obvious how you run into this situation. For…


Static Fields

By default, static fields are scoped to AppDomains. In other words, each AppDomain gets its own copy of all the static fields for the types that are loaded into that AppDomain. This is independent of whether the code was loaded as domain-neutral or not. Loading code as domain neutral affects whether we can share the…