Re: Java JNI && MzScheme?

[Matthew Flatt <mflatt@cs.utah.edu>]

This is a reply for a message that I lost track of long ago (so long
ago that Giorgio might no longer care about an answer).

Quoting Giorgio Scorzelli:
> I'm trying to create a Windows DLL that implements a NATIVE method of
> a Java class (see JNI documentation) and which should embed inside the
> well-known MzScheme interpreter.

The main problem is that the JVM will likely execute multiple threads,
and the threads will likely confuse MzScheme (or, more specifically,
its GC).

> I execute in my DLL the following action :
> 
> JNIEXPORT jstring JNICALL Java_PlasmServer_Eval(JNIEnv *env, jclass obj, jstring cmd)
> {
> 	Scheme_Env* env=scheme_basic_env();//PROBLEM HERE!!!
> 	[...]
> }

It might be enough to set the variable GC_use_registered_statics to 1
before calling scheme_basic_env(). That "magically" avoids certain
thread problems in Windows.

Others have reported problems in embedding MzScheme into a
multithreaded app, and I don't think we've discovered all the problems
and solutions. For some platforms, the stack base is a problem; in
version 199.x, GC_use_registered_statics has been replaced/extended by
a scheme_set_stack_base() function that takes two arguments: a stack
base or NULL (= auto-find stack), and a flag indicating whether to
auto-find static variables.

Matthew