IKVM.NET

If you're going to the PDC and want to chat, let me know.

I'm not a big fan of serialization, but there is one use that makes sense to me; intra-process, cross-AppDomain serialization. If you have ever done any cross-AppDomain work with IKVM you've probably run into the situation where a Java ... [More] exception couldn't be serialized across the AppDomain boundary. I've finally addressed this by building automatic (oneway) serialization interop support into IKVM. This means that most Java classes that are serializable should now automatically become .NET serializable. There are, however, some important caveats: Serialized streams will not be compatible between different IKVM releases. This is intended *only* for cross-AppDomain serialization between different instances of the same IKVM code. ObjectOutputStream.writeUnshared() and ObjectInputStream.readUnshared() have not been implemented. So any classes that rely on those will fail to serialize/deserialize. Instances of dynamically loaded Java classes and statically (ikvmc) compiled classes that implement readResolve() will fail deserialization if they (directly or indirectly) serialize self references. Deserialization ordering may be different, meaning that if a class has a custom deserialization method, it may encounter objects that have not been completely deserialized. Under some circumstances, a class that implements readResolve() may have its readResolve() method called twice on the same object. When a ghost array is serialized, it is serialized as an object[] (i.e. it loses its specific type). Again, any Java class that is serializable (i.e. that implements java.io.Serializable or java.io.Externalizable and follows the associated rules) is generally automatically .NET serializable. There are a couple of exceptions where ikvmc and the runtime will assume that your class wants to handle its own .NET serialization: If the class has the @cli.System.SerializableAttribute.Annotation annotation. If the class (or one of its base classes) implements cli.System.Runtime.Serialization.ISerializable. If the class (or one of its base classes) implements cli.System.Runtime.Serialization.IObjectReference. If the class has a GetObjectData method. If the class has a .NET deserialization constructor. Using the .NET custom serialization custom attributes OnDeserializedAttribute, OnDeserializingAttribute, OnSerializedAttribute or OnSerializingAttribute does not interfere with getting automatic serialization support (and the .NET serialization engine will call the annotated methods at the appropriate times). Inheritance - Extending Java classes in .NET When you want to subclass a serializable Java class in (e.g.) C# and make your subclass serializable as well, you need to do two simple things: Add a [Serializable] attribute to your class. Add a .NET deserialization constructor that calls the base class constructor and does nothing else. Here's an example of extending java.util.ArrayList: [Serializable] class MyList : java.util.ArrayList {   private int exampleField;   public MyList()   {   }   protected MyList(SerializationInfo info, StreamingContext context)     : base(info, context)   {   } } MyList is now .NET serializable and exampleField will automatically be serialized/deserialized. Inheritance - Extending .NET classes in Java For this scenario, nothing has really changed. You still need to follow the standard .NET rules for creating serializable types. Serializing .NET objects in Java The automatic serialization interop is only one way, so you won't be able to serialize .NET objects using Java serialization (unless they happen to implement java.io.Serializable.__Interface or java.io.Externalizable). I currently have no plans to implement this functionality. [Less]

Another minor update. Changes: Changed version to 0.40.0.3 Fixed regression introduced in 0.40 that caused ikvmc -classloader:<class> option to fail if <class> wasn't public. ... [More] Fixed regression introduced in 0.40 that caused ikvmstub on core class libraries to fail. Fixed #2829717. Binaries available here: ikvmbin-0.40.0.3.zip. Sources: ikvm-0.40.0.3.zip, classpath-0.95-stripped.zip, openjdk6-b12-stripped-IKVM-0.40.zip [Less]

In December 2006 I reported a critical .NET security vulnerability to Microsoft. When I found the the issue it had already been fixed in Vista, but it still took them until July 2007 to release a fix for XP. Seven months, I thought ... [More] that was pretty bad. In September 2008 I reported another critical .NET security vulnerability to Microsoft. The fix for this issue was trivial and made it into the subsequent Silverlight 2.0 RTM on October 13th. This week the July patches were released and for the tenth month no security bulletin about this issue. Wednesday I mailed the Microsoft Security Response Center to ask what the status is. I received no reply. So I decided to investigate. I quickly discovered that my main (Vista) system was already patched (!). After some digging I found that on XP, Windows Update offers KB951847 which contains a fix. The KB article makes no mention of any security fixes, nor is there a corresponding security bulletin. If this is Microsoft's idea of responsible disclosure, then maybe I should also apply my "no Microsoft bug filing" policy to security issues. [Less]

It's been a while since the previous snapshot, but I haven't been sitting around idle. Besides the fixes to IKVM.Reflection.Emit, which were part of secret prototype project I've been working on (and may or may not announce at some point ... [More] in the future :-)), I've also been working on IKVM.NET itself. I did a bunch of work to improve startup (at least for "core" classes). In particular, many scenarios should now be possible without initializing the reflection machinery. Here are some examples:   IKVM 0.40 IKVM 0.41.3484       x86 JIT     x86 NGEN             x86 JIT     x86 NGEN     2nd invocation obj = Float.TYPE 12.4 1.56 0.280 0.0152 0.0041 System.out.println("Hello World") 275 12.8 114 8.90 0.0569 new StringBuffer() 129 10.8 6.34 0.0866 0.0041 Charset.forName("windows-1252") 267 13.7 77.4 7.87 0.0028 Times are in milliseconds and (except for the last column) show the time it takes to execute the code snippet on the left as the very first Java code in the process. I added the "2nd invocation" column to emphasize that these large times are due to JIT and/or initialization costs. Things have clearly improved, but it should also be clear that when you care about startup time, you really need to look into using NGEN. I should point out that currently only the "windows-1252" (and UTF-8) charsets are eagerly constructed to avoid reflection, if you care about another charset, let me know and I will add it (unless your charset isn't in IKVM.OpenJDK.Core.dll, then you're out of luck.) Changes: More AWT/Swing work.. Removed more GNU Classpath remnants. Added rmi stub generation to build process, instead of relying on .class files in stripped zip. Added "RuntimeCompatibilityAttribute(WrapNonExceptionThrows = true)" to generated assemblies. Added ikvmc warnings for VerificationError and ClassFormatError. Added -baseaddress:<address> option to ikvmc. Fixed ikvmc to skip empty lines in response file, instead of throwing an exception. Split XML assembly into eight parts. Thanks to Michael Kay for helping out with this. Changed build to put x86 specific binaries in bin-x86 directory and x64 specific binaries in bin-x64. jvm.dll is now always built in both flavors. Unfortunately, ikvm-native still needs to be built separately. Split core library into several more assemblies. Added step to build process to automatically compute a base address for core library assemblies. This should make ngen-ed images more efficient (if the images can be loaded at their preferred base addresses). Added a mechanism to the build to prevent accidentally introducing new dependencies between the OpenJDK assemblies. Fixed bug that caused startup properties set with ikvm.runtime.Startup.setProperties() to be forgotten when doing a System.setProperties(null). Forked java.io.ObjectStreamField to make signature computation lazy. Made ikvm.runtime.Util.getInstanceTypeFromClass() into an instrinsic, when used with a class literal. Optimized class literals that reference statically compiled classes (at a slight cost to dynamically compiled classes). Optimized primitive class literals. Added codegen optimization for reading unsigned bytes from a byte array (buf[i] & 0xFF or buf[i] 0x0FFL). Made callerID initialization lazy. Forked sun/nio/cs/StandardCharsets.java to eagerly create MS1252 and UTF-8 charsets, to avoid reflection (at least in Western Europe, if you want another charset added, just let me know.) Several other minor optimizations. Binary available here: ikvmbin-0.41.3484.zip [Less]

I have done a massive amount of fixes to IKVM.Reflection.Emit to make it full featured (even though it still doesn't implement all Reflection.Emit APIs, the functionality should (almost) all be there, for example via different ... [More] overloads). I completed support for generics (I think) and fixed many bugs in that area, ikvmc only uses a very small amount of generics so these fixes are unlikely to affect it. It's worth explicitly stating the design goals of IKVM.Reflection.Emit: It's a write-only API. Some GetXXX methods or properties may be implemented, but that's mostly for its internal convenience. There is intentionally no error checking. During ikvm development the error checking in System.Reflection.Emit has cost me a huge amount of time, it is generally much easier to diagnose the problem when you have a broken assembly file. PEverify and ILDASM are your friends. Code that uses System.Reflection.Emit in a write-only way is supposed to "just work" (modulo missing APIs, but those changes should be trivial). I've done some pretty heavy duty testing on it. It should be ready for external (i.e. non-ikvmc) usage now. If you decide to use it (or consider using it), please let me know. As always, feedback is appreciated. Changes: Added support for ByRef and Pointer types. Completed support for all literal field constant types and fixed null literal fields. Added ModuleBuilder.DefineInitializedData(). Fixed many generics related bugs. Added a (non-standard) API to ModuleBuilder to set the PE image base address. Added TypeBuilder.SetParent(). Added TypeBuilder.GetMethod() and TypeBuilder.GetConstructor() to instantiate methods on generic types. Added a (non-standard) API to ILGenerator to disable the "helpful" automatic leave/endfinally instructions in exception blocks. Added support for pinned local variables. Added UIntPtr and TypedReference signature encodings. Fixed handling of TypeBuilder enums in custom attributes. Added MethodBuilder.SetSignature(). Added GenericTypeParameterBuilder.SetInterfaceConstraints() and .SetGenericParameterAttributes(). Fixed (Method|Type)Builder.SetCustomAttribute() to set HasSecurity flag when SuppressUnmanagedCodeSecurityAttribute is set. Added support for defining events. Binary available here: ikvm-refemit-0.41.3464.zip [Less]

A minor update. Changes: Changed version to 0.40.0.2 Changed build to generate rmi stubs instead of depend on .class files in openjdk6-b12-stripped-IKVM-0.40.zip. Thanks to Jo Shields for helping with ... [More] this. Fixed verifier bugs. Thanks to Brian Heineman for reporting this. Binaries available here: ikvmbin-0.40.0.2.zip. Sources: ikvm-0.40.0.2.zip, classpath-0.95-stripped.zip, openjdk6-b12-stripped-IKVM-0.40.zip [Less]

I've released IKVM 0.40 to SourceForge. The binaries are identical to the ones in release candidate 1. Release Notes This document lists the known issues and incompatibilities. Runtime Code ... [More] unloading (aka class GC) is not supported. In Java static initializers can deadlock, on .NET some threads can see uninitialized state in cases where deadlock would occur on the JVM. JNI Only supported in the default AppDomain. Only the JNICALL calling convention is supported! (On Windows, HotSpot appears to also support the cdecl calling convention). Cannot call string contructors on already existing string instances A few limitations in Invocation API support The Invocation API is only supported when running on .NET. JNI_CreateJavaVM: init options "-verbose[:class|:gc|:jni]", "vfprintf", "exit" and "abort" are not implemented. The JDK 1.1 version of JavaVMInitArgs isn't supported. JNI_GetDefaultJavaVMInitArgs not implemented JNI_GetCreatedJavaVMs only returns the JavaVM if the VM was started through JNI or a JNI call that retrieves the JavaVM has already occurred. DestroyJVM is only partially implemented (it waits until there are no more non-daemon Java threads and then returns JNI_ERR). DetachCurrentThread doesn't release monitors held by the thread. Native libraries are never unloaded (because code unloading is not supported). The JVM allows any reference type to be passed where an interface reference is expected (and to store any reference type in an interface reference type field), on IKVM this results in an IncompatibleClassChangeError. monitorenter / monitorexit cannot be used on unitialized this reference. Floating point is not fully spec compliant. A method returning a boolean that returns an integer other than 0 or 1 behaves differently (this also applies to byte/char/short and for method parameters). Synchronized blocks are not async exception safe. Ghost arrays don't throw ArrayStoreException when you store an object that doesn't implement the ghost interface. Class loading is more eager than on the reference VM. Interface implementation methods are never really final (interface can be reimplemented by .NET subclasses). JSR-133 finalization spec change is not fully implemented. The JSR-133 changes dictate that an object should not be finalized unless the Object constructor has run successfully, but this isn't implemented. Static Compiler (ikvmc) Some subtle differences with ikvmc compiled code for public members inherited from non-public base classes (so called "access stubs"). Because the access stub lives in a derived class, when accessing a member in a base class, the derived cctor will be run whereas java (and ikvm) only runs the base cctor. Try blocks around base class ctor invocation result in unverifiable code (no known compilers produce this type of code). Try/catch blocks before base class ctor invocation result in unverifiable code (this actually happens with the Eclipse compiler when you pass a class literal to the base class ctor and compile with -target 1.4). Only code compiled in a single assembly fully obeys the JLS binary compatibility rules. An assembly can only contain one resource with a particular name. Passing incorrect command line options to ikvmc may result in an exception rather than a proper error messages. Class Library Most class library code is based on OpenJDK 6 build 12. Below is a list of divergences and IKVM specific implementation notes. com.sun.security.auth.module        Not implemented. java.applet GNU Classpath implementation. Not implemented. java.awt GNU Classpath implementation with partial System.Windows.Forms based back-end. Not supported. java.io.Console Not implemented. java.lang.instrument Not implemented. java.lang.management Not implemented. java.net No IPv6 support implemented. java.net.ProxySelector Getting the default system proxy for a URL is not implemented. java.text.Bidi GNU Classpath implementation. Not supported. java.util.zip Partially based on GNU Classpath implementation. javax.imageio.plugins.jpeg Partial implementation. JPEGs can be read and written, but there is no metadata support. javax.management Not implemented. javax.print Not implemented. javax.script Not implemented. javax.smartcardio Not implemented. javax.sound Not implemented. javax.swing GNU Classpath implementation. Not supported. javax.tools Not implemented. org.ietfs.jgss Not implemented. sun.jdbc.odbc Implementation based on .NET ODBC managed provider. sun.net.www.content.audio Audio content handlers not implemented. sun.net.www.content.image Image content handlers not implemented. The entire public API is available, so "Not implemented." for javax.print, for example, means that the API is there but there is no back-end to provide the actual printing support. "Not supported." means that the code is there and probably works at least somewhat, but that I'm less likely to fix bugs reported in these areas. Specific API notes: java.lang.Thread.stop(Throwable t) doesn't support throwing arbitrary exceptions on other threads (only java.lang.ThreadDeath). java.lang.Thread.holdsLock(Object o) causes a spurious notify on the object (this is allowed by the J2SE 5.0 spec). java.lang.String.intern() strings are never garbage collected. Weak/soft references and reference queues are inefficient and do not fully implement the required semantics. java.lang.ref.SoftReference: Soft references are not guaranteed to be cleared before an OutOfMemoryError is thrown. Threads started outside of Java aren't "visible" (e.g. in ThreadGroup.enumerate()) until they first call Thread.currentThread(). java.lang.Thread.getState() returns WAITING or TIMED_WAITING instead of BLOCKING when we're inside Object.wait() and blocking to re-acquire the monitor. java.nio.channel.FileChannel.lock() shared locks are only supported on Windows NT derived operating systems. java.lang.SecurityManager: Deprecated methods not implemented: classDepth(String), inClass(String), classLoaderDepth(), currentLoadedClass(), currentClassLoader(), inClassLoader() Supported Platforms This release has been tested on the following CLI implementations / platforms: CLI Implementation       Architecture      Operating System .NET 2.0 SP2 x86 Windows .NET 2.0 SP2 x64 Windows Partial Trust There is experimental support for running in partial trust.   [Less]

Class gc support has now been checked in (but is not available in the attached binaries, because they've been built for .NET 2.0). This is somewhat of a milestone snapshot, because it is the first version that no longer requires GNU ... [More] Classpath to build*. However, please note that AWT / Swing still needs a lot of work. *What this means is that there is no longer an external dependency on GNU Classpath. There is still GNU Classpath derived code in ikvm's source tree. For example, small parts of AWT and the pure Java  implementation of java.util.zip. Changes: Removed dependency on classpath-0.95-stripped.zip. All AWT / Swing code is now from OpenJDK or in the ikvm codebase. Defined NET_4_0 when building on .NET 4.0 to enable conditional code. Changed IKVM.Reflection.Emit's ModuleBuilder and AssemblyBuilder to extends Module and Assembly respectively when building on .NET 4.0. Added .NET 4.0 fix to IKVM.Reflection.Emit (for the fact that Type now defines == operator). Fixed locking for image based Graphics. Various changes to remove warnings when building on .NET 4.0. Several fixes related to dynamic assemblies. Several improvements to better work in partial trust. More AWT work. Made java.lang.reflect.Field exception messages the same as JDK 6. Implemented class gc (for .NET 4.0 builds). Added -Xnoclassgc option to ikvm (only meaningful in a .NET 4.0 build). Binaries available here: ikvmbin-0.41.3440.zip. [Less]

Back in the PDC build of .NET 4.0 another interesting new feature was introduced: ConditionalWeakTable<TKey, TValue>. This is a special purpose dictionary to associate objects with other objects. It was introduced to help the DLR, ... [More] which needs the ability to add properties to arbitrary objects. The documentation is pretty clear and the CLR team blog also has some info on it, so I won't rehash that. Instead I'll just mention that ConditionalWeakTable itself is not a magic type (i.e. the runtime knows nothing about it), but instead it is built on top of a private value type System.Runtime.Compiler.Services.DependentHandle. DependentHandle is essentially a handle based ephemeron implementation. JVM vs CLR This means that the CLR now comes a bit closer to the JVM in terms of memory management features. The JVM has had some very interesting reference types for a long time (WeakReference, SoftReference and PhantomReference) and the ability to have these references posted to a ReferenceQueue by the GC when the relevant change in reachability to the referenced object occurs. Unfortunately there still isn't parity between the CLR and JVM, even though the CLR now provides a capability the JVM doesn't. Java .NET Notes ReferenceQueue n/a   WeakReference WeakReference (short) .NET has no ReferenceQueue equivalent notification mechanism. n/a WeakReference (long)     SoftReference n/a   PhantomReference     n/a   WeakHashMap n/a   n/a ConditionalWeakTable   (If you think that Java's WeakHashMap and .NET's ConditionalWeakTable are similar, consider that ConditionalWeakTable is ephemeron based. Plus the fact that WeakHashMap uses short weak references and ConditionalWeakTable uses long weak references.) IKVM.NET ConditionalWeakTable is very useful for IKVM in several places: Used to support class unloading by mapping Assembly to ClassLoader. Used in caching of MethodBase properties. Can be used to track the type of ghost arrays. Can be used to more efficiently implement adding references to a ReferenceQueue. Java Given the effort going into Java 7 to improve support for dynamic languages it would not be surprising nor unwelcome to see ephemerons being added to the JVM. [Less]