Integration with Threads

MzScheme's threads can break external C code under two circumstances:

• Pointers to stack-based values can be communicated between threads. For example, if thread A stores a pointer to a stack-based variable in a global variable, if thread B uses the pointer in the global variable, it may point to data that is not currently on the stack.
• C functions which can invoke MzScheme (and also be invoked by MzScheme) depend on strict function-call nesting. For example, suppose a function F uses an internal stack, pushing items on to the stack on entry and popping the same items on exit. Suppose also that F invokes MzScheme to evaluate an expression. If the evaluate on this expression invoked F again in a new thread, but then returns to the first thread before completeing the second F, then F's internal stack will be corrupted.