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40.15 Memory Layout

CMUCL has four spaces, read-only, static, dynamic-0, and dynamic-1. Read-only contains objects that the system never modifies, moves, or reclaims. Static space contains some global objects necessary for the system’s runtime or performance (since they are located at a known offset at a known address), and the system never moves or reclaims these. However, GC does need to scan static space for references to moved objects. Dynamic-0 and dynamic-1 are the two heap areas for stop-and-copy GC algorithms.

What global objects are at the head of static space???

   NIL
   eval::*top-of-stack*
   lisp::*current-catch-block*
   lisp::*current-unwind-protect*
   FLAGS (RT only)
   BSP (RT only)
   HEAP (RT only)

In addition to the above spaces, the system has a control stack, binding stack, and a number stack. The binding stack contains pairs of descriptors, a symbol and its previous value. The number stack is the same as the C stack, and the system uses it for non-Lisp objects such as raw system pointers, saving non-Lisp registers, parts of bignum computations, etc.