Ovm

Ovm is a tool that specializes in generating virtual machines for free-standing applications. It comes packed with compilers, threading systems, and garbage collectors that cater to specific applications, including Java programs and those developed for the Real-time Specification for Java. Ovm's key features include dynamic loading, weak references, finalization, and JNI support, although the latter is not currently planned. Users need to adapt certain codes to work seamlessly with Ovm due to its limitations in dynamic loading, finalizers, and native calls.

Ovm is in its BETA stage and has known bugs that could lead to unexpected behavior. The tool requires Java 1.4 and gcc 3.x, as well as 256MB of main memory, even though 1GB is recommended. To ensure that applications work as desired, it is best to compile them against Ovm's version of the JDK based on GNU classpath. Users should refer to the TUTORIAL file provided to learn how to compile and run Java codes, including the SPEC JVM and the real-time benchmarks.

Ovm needs whole-world compilation of the application and has three execution backends— an interpreter, JIT, and J2C— intended for development purposes. However, only the J2C configuration with gcc-3.4 can cater to all benchmarking. The program's limitations are few, with the only major one being that the Ovm program may occasionally hang following a subprocess call. This bug is more typical in Blackdown Java distributions than it is in Sun, and Ovm tries to detect and resolve the problem. Users can use -Z to stop the process and then fg. to restart it, which usually unhangs things.