Hello, and other things

[Jason Fordham]

Hi all,

I was drawn into this list by the news today that Jonathan Schwartz was 
interested in making the JVM into Just Another VM. Coincidentally (and 
this is the spur to my enthusiasm), I started thinking about targeting 
GCC for the JVM last week.

It quickly became clear that the JVM instruction set is designed to make 
the C programming model difficult: the separation of bytecodes, stacks, 
frames, and object space, and the generally unconvertible addressType 
quickly led me to a model where the JVM stacks are ignored except for 
primitive operations, while memory - for data, bss and heap - is modeled 
in a large array. In order to model C's function calls by pointer, I 
figured a handle pair, class and method, hashing the strings, with a 
linking stage after compilation to perform fixup - much as I imagine 
slide 17 in the LangNet presentation implies.

The key obstacles I see are that the instruction set makes implementing 
a C-like stack expensive: there are no neat push and pop operations for 
this memory model, it feels like microcoding. Though I understand the 
motivation, which is to protect the bytecodes from malicious or lazy use 
of buffer overflows, and other mechanisms for executing data.

I like the method handle mechanism, for a variety of reasons, and I 
would like to see some easing up on where the a stack is located so that 
operations which index into the stack are more flexible, and fast. Is 
this possible?

Jason