CLRHack: unwind-protect and catch-throw

Handling of unwind-protect The CLRHack compiler maps Lisp unwind-protect semantics directly onto the Structured Exception Handling (SEH) infrastructure of the .NET Common Language Runtime (CLR). Specifically, it utilizes the try...finally construct provided by the Common Intermediate Language (CIL). Lisp semantics require that the cleanup forms in an unwind-protect block be executed regardless of how control leaves the protected form—whether via normal return, a non-local throw, or a lexical exit like return-from. The CLR guarantees that a finally block will execute during stack unwinding, which is exactly the hook required for Lisp. The implementation details are as follows: Protected Form: The compiler generates the code for the protected form inside a CIL try block. Upon successful completion, the primary return value is stored in a local variable, and a leave instruction is used to exit the try block, which automatically triggers the transition to the finally block. Side-Channel…