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[yvm] low performance garbage-collectable jvm
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y1yang0/yvm
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This is a toy Java virtual machine(JVM) that supports many of Java's language features, it also comes with an experimentalmark-sweep garbage collector. The implementation of this JVM follows theJava Virtual Machine Specification 8. I don't have enough time to write unit tests for each component, and I don't implement the full Java language features, but as far as pleasing myself, I think it's enough. If you find any bugs, or you want to implement any missing features, you can create an issue or pull request, respectively.
# Note, C++14 is required at least.$cd yvm$ cmake.$ make$ ./yvmUsage: yvm --lib=<path><main_class> --lib=<path> Tells YVM where to find JDK classes(java.lang.String, etc)<main_class> The full qualified Java class name, e.g. org.example.Foo$ ./yvm --lib=/path/to/yvm/bytecode ydk.test.QuickSort0 1 1 1 1 1 4 4 4 5 6 7 7 9 9 9 12 74 96 98 8989
Advanced language features will support later, you can also create PR to contribute your awesome code.Implemented features are as follows:
- Java arithmetic, flow control, object-oriented programming(virtual method, inherit,etc.)
- Runtime type identification
- String concatenation
- Exception handling
- Async native threads
- Synchronized block with object lock
- Garbage Collection(With mark-and-sweep policy)
You can find some examples athere.
loadJavaClass("org.example.Foo")- findJavaClass if present
- Otherwise, loadJavaClass from --lib, all classes is stored in ClassSpace
linkJavaClass("org.example.Foo")- Initialize static fields with default value
initJavaClass("org.example.Foo")- Invoke
org.example.Foo.<clinit>
- Invoke
invokeByName("org.example.Foo","main","([Ljava/lang/String;)V")- Prepare execution frame
- Find method from JavaClass
execByteCodede- Interprete every bytecode on simulated stack
- Recursively call
execByteCodedewhen performinginvoke*bytecodes
root@ubuntu:~/yvm/src$ tree..├── classfile │ ├── AccessFlag.h# Access flag of class, method, field│ ├── ClassFile.h# Parse .class file│ └── FileReader.h# Read .class file├── gc│ ├── Concurrent.cpp# Concurrency utilities│ ├── Concurrent.hpp│ ├── GC.cpp# Garbage collector│ └── GC.h├── interpreter│ ├── CallSite.cpp# Call site to denote a concrete calling│ ├── CallSite.h│ ├── Internal.h# Types that internally used│ ├── Interpreter.cpp# Interpreter│ ├── Interpreter.hpp│ ├── MethodResolve.cpp# Resolve call site│ └── MethodResolve.h├── misc│ ├── Debug.cpp# Debugging utilities│ ├── Debug.h│ ├── NativeMethod.cpp# Java native methods│ ├── NativeMethod.h│ ├── Option.h# VM arguments and options│ ├── Utils.cpp# Tools and utilities│ └── Utils.h├── runtime│ ├── JavaClass.cpp# Internal representation of java.lang.Class│ ├── JavaClass.h│ ├── JavaException.cpp# Exception handling│ ├── JavaException.h│ ├── JavaFrame.cpp# Execution frame│ ├── JavaFrame.hpp│ ├── JavaHeap.cpp# Java heap, where objects are located│ ├── JavaHeap.hpp│ ├── JavaType.h# Java type definitions│ ├── ClassSpace.cpp# Store JavaClass│ ├── ClassSpace.h│ ├── ObjectMonitor.cpp# synchronized(){} block implementation│ ├── ObjectMonitor.h│ ├── RuntimeEnv.cpp# Runtime structures│ └── RuntimeEnv.h└── vm ├── Main.cpp# Parse command line arguments ├── YVM.cpp# Abstraction of virtual machine └── YVM.h
See its wiki for more development details.
Code licensed under the MIT License.