Jeannie: Granting Java Native Interface Developers Their Wishes Martin Hirzel Robert Grimm IBM Watson Research Center New York University
[email protected] [email protected] Abstract higher-level languages and vice versa. For example, a Java Higher-level languages interface with lower-level languages project can reuse a high-performance C library for binary such as C to access platform functionality, reuse legacy li- decision diagrams (BDDs) through the Java Native Inter- braries, or improve performance. This raises the issue of face [38] (JNI), which is the standard FFI for Java. how to best integrate different languages while also recon- FFI designs aim for productivity, safety, portability, and ciling productivity, safety, portability, and efficiency. This efficiency. Unfortunately, these goals are often at odds. For paper presents Jeannie, a new language design for integrat- instance, Sun’s original FFI for Java, the Native Method In- ing Java with C. In Jeannie, both Java and C code are nested terface [52, 53] (NMI), directly exposed Java objects as C within each other in the same file and compile down to JNI, structs and thus provided simple and fast access to object the Java platform’s standard foreign function interface. By fields. However, this is unsafe, since C code can violate Java combining the two languages’ syntax and semantics, Jean- types, notably by storing an object of incompatible type in a nie eliminates verbose boiler-plate code, enables static error field. Furthermore, it constrains garbage collectors and just- detection across the language boundary, and simplifies dy- in-time compilers, since changes to the data representation namic resource management.