# Wednesday, 02 July 2014
New Development Snapshot

I fixed a whole bunch of weird edge case behaviors and finally did the first part of the lambda performance work.

Here are some rough performance results (times in milliseconds) for this crude microbenchmark:

iteration IKVM 8.0.5274 IKVM 8.0.5296 JDK 1.8.0_05                     ikvmc ngen
1 1040.2 87.6 71.8   1.3 0.4
2 0.9 0.3 0.3   0.3 0.4
3 0.9 0.3 0.3   0.3 0.4

Only LambdaMetafactory.metafactory() is supported at the moment. LambdaMetafactory.altMetafactory() will follow in a future snapshot.


  • Removed sun.misc.Unsafe usage from java.util.concurrent.atomic.Striped64.
  • Bug fix. Handle malformed UTF-16 (invalid surrogates) in type/member names and annotations.
  • Added ikvm.exe.manifest file to enable Windows 8.1 behavior (including getting the right version number).
  • Bug fix. Invokedynamic bootstrap method can also be a constructor.
  • Bug fix. Improved handling of incorrect invokedynamic bootstrap methods.
  • Bug fix. Non-canonical modified UTF-8 encodings should throw ClassFormatError.
  • Changed ClassFormatError message for invalid UTF-8 to match JDK.
  • Bug fix. Array classes get the system protection domain, not the element type's.
  • Bug fix. Interfaces can't "override" final methods in Object.
  • Bug fix. Only the bootstrap class loader is allowed to define classes in the java package.
  • Bug fix. Since Java 1.7 class names aren't allowed to have [ and ] characters.
  • Updated ldc error behavior to match Java 8.
  • Bug fix. Calling BasicFileAttributes.size() on a directory didn't work. Thanks to Lucius Junevicus for reporting this.
  • Bug fix. If an invokedynamic bootstrap argument conversion fails, the exception should not be wrapped in BootstrapMethodError.
  • Added intrinsic for invokedynamic using LambdaMetafactory.metafactory().

Binaries available here: ikvmbin-8.0.5296.zip

Wednesday, 02 July 2014 13:43:42 (W. Europe Daylight Time, UTC+02:00)  #    Comments [0]
# Friday, 13 June 2014
Malformed UTF-16

While scanning the Java 8 version of the JVM spec for changes, I noticed this new text:

Names of methods, fields, local variables, and formal parameters are stored as unqualified names. An unqualified name must contain at least one Unicode code point and must not contain any of the ASCII characters . ; [ / (that is, period or semicolon or left square bracket or forward slash).

As per usual, the spec and HotSpot implementation don't agree on the details. In particular the text says that a name must contain at least one Unicode code point. At this point it becomes important what a Unicode code point actually is. Suffice it to say that a single UTF-16 code unit in the surrogate range is not a valid Unicode code point and that such names are accepted by HotSpot without any complaint.

The spec, of course, is also incomplete as it does not address what should happen in case of malformed UTF-16 in general. Or maybe it should just be changed to say "... UTF-16 code unit ..." to match the current behavior and not worry about surrogates at all.

On the .NET side, the strings that aren't string literals in the code are stored as UTF-8 and the ECMA CLI spec requires valid UTF-8, but this is only partially enforced which poses its own set of problems.

After discovering all this, I felt compelled to fix IKVM.NET to behave similarly to HotSpot in this regard and added support for escaping malformed UTF-16 strings when writing metadata and unescaping them when reading it back in.

Finally, let's end with a C# example that shows some of the weirdness on the .NET side:

using System;
using System.ComponentModel;

class Surrogate {
  static void Main() {
    var attr = (DisplayNameAttribute)typeof(Surrogate)
    Console.WriteLine(attr.DisplayName == "\uD800");
Friday, 13 June 2014 13:43:41 (W. Europe Daylight Time, UTC+02:00)  #    Comments [2]
# Tuesday, 10 June 2014
New Development Snapshot

I implemented Type Annotation reflection and fixed a couple of bugs.


  • Implemented type annotation reflection.
  • Bug fix. Process exec should support quotes around filename for VFS executables.
  • Bug fix. Process exec should eagerly close the redirected in/outputs when an exception occurs or immediately after the process exits.
  • Bug fix. ProtectionDomain stack walk should ignore "HideFromStackWalk" frames.
  • Include some missing resources.
  • Added security attributes needed for .NET 4 build.

Binaries available here: ikvmbin-8.0.5274.zip
Sources: ikvmsrc-8.0.5274.zip and openjdk-8-b132-stripped.zip

Tuesday, 10 June 2014 10:19:57 (W. Europe Daylight Time, UTC+02:00)  #    Comments [0]
# Wednesday, 04 June 2014
New Development Snapshot

More progress on the OpenJDK 8 integration and a couple of unrelated fixes.

I fixed an incompatibility with Mono (and other ECMA compliant tools that parse custom attributes). When I changed package manifest handling in 7.4 to handle reading the manifest from the right jar I unknowingly chose a custom attribute encoding that works on the CLR, but isn't actually ECMA compliant. Mono has since added support for this encoding.

Another somewhat interesting change is that I added an (internal only) feature to make it easier to replace sun.misc.Unsafe.compareAndSet() with Interlocked.CompareExchange. The trigger was the new reflection data caching in java.lang.Class. Here's an example of what it looks like:

static native boolean casReflectionData(Class<?> clazz,
                                        SoftReference<ReflectionData<T>> oldData,
                                        SoftReference<ReflectionData<T>> newData);

The ikvmc compiler will generate a method body that uses Interlocked.CompareExchange<T>() to update the reflectionData field in Class. In other places where I previously used Interlocked methods (e.g. java.util.concurrent.AtomicReferenceArray) I implemented the method body in map.xml using MSIL instructions, but here the generic version of CompareExchange is needed and I didn't want to invent a syntax for instantiating a generic method in map.xml.

Oracle is working on adding atomic operations to Java and I suggested this annotation based approach, but it was rejected because "we don't add language semantics through annotations".


  • Implemented method parameter reflection.
  • Compile class library with javac -parameters option to get parameter names for abstract and native methods.
  • Added (undocumented) -noparameterreflection option ikvmc to disable emitting method parameter reflection metadata
  • Enabled MethodParameter attribute in runtime stub generator.
  • Support round tripping malformed MethodParameter attribute in stub generator.
  • Fixed PackageListAttribute to be ECMA compliant.
  • Added support for defining abstract methods in remap file.
  • Implemented sun.nio.ch.Net.poll() native method.
  • Replaced sun.misc.Unsafe cas operations in java.lang.Class with Interlocked.CompareExchange().
  • Replaced AtomicReference[Array].getAndSet() implementations with Interlocked.Exchange() based implementations.
  • Fixed Linux build. Thanks to Joan Karadimov for reporting this.
  • Prevent unfocable windows from being activated by mouse click. (Based on patch by Maria Papendieck of pure-systems.)
  • Fixed clipboard access to use the right thread. (Based on patch by Maria Papendieck of pure-systems.)
  • IKVM.Reflection: Added UniverseOptions.DecodeVersionInfoAttributeBlobs to support decoding CustomAttributeBuilder with blob to extract version info fields.

Binaries available here: ikvmbin-8.0.5268.zip
Sources: ikvmsrc-8.0.5268.zip and openjdk-8-b132-stripped.zip

Wednesday, 04 June 2014 09:30:36 (W. Europe Daylight Time, UTC+02:00)  #    Comments [4]
# Monday, 26 May 2014
New Development Snapshot

More progress on the OpenJDK 8 integration.


  • Integrated Nashorn.
  • Added workaround for bug in .NET 2.0 implementation of ModuleBuilder.GetMethodToken() exposed by Nashorn.
  • Bug fix. A .NET type should always have access to its nested types.
  • Fixed javap build.
  • Bug fix. The MethodHandle code requires the volatile field accessors in Unsafe for volatile field access.
  • Bug fix. Handle more than 8 parameters in invokedynamic.
  • Bug fix. DynamicMethod's ILGenerator doesn't like unbaked array types.
  • Bug fix. MethodHandle.invoke[Exact] methods should have VarArgs flag set.
  • Added workaround for javac MethodHandle.invoke[Exact] detection bug.
  • Moved cldrdata and localedata into separate assemblies.
  • Implemented native methods for HostLocaleProviderAdapterImpl. The system property "java.locale.providers" can now be set to "HOST" to use the .NET locale implementation.

Binaries available here: ikvmbin-8.0.5259.zip
Sources: ikvmsrc-8.0.5259.zip and openjdk-8-b132-stripped.zip

Monday, 26 May 2014 10:22:29 (W. Europe Daylight Time, UTC+02:00)  #    Comments [0]