Still still doesn't compile. Progress is being made, but it's fair awfy slow.

src/c/payloads/cons.h

@@ -12,20 +12,13 @@
 #include <stdbool.h>
 
 #include "memory/pointer.h"
+#include "memory/pso2.h"
 #include "memory/pso4.h"
 
 #define CONS_SIZE_CLASS 2
 
-/**
- * @brief A cons cell.
- * 
- */
-struct cons_payload {
-  /** Contents of the Address Register, naturally. */
-    struct pso_pointer car;
-  /** Contents of the Decrement Register, naturally. */
-    struct pso_pointer cdr;
-};
+/* NOTE THAT the definition of a cons payload has to be in memory/pso2.h to
+ * avoid circularity. */
 
 struct pso_pointer car( struct pso_pointer frame_pointer );
 

src/c/payloads/exception.c

@@ -132,7 +132,7 @@ struct pso_pointer throw_exception_with_cause( struct pso_pointer location,
 	} else {
 		struct pso_pointer x_frame = inc_ref(make_frame(
 			2, frame_pointer, message,
-			(nilp(location)
+			(c_nilp(location)
 				 ? nil
 				 : make_cons(frame_pointer,
 							 make_cons(frame_pointer,

src/c/payloads/exception.h

@@ -30,4 +30,8 @@ struct pso_pointer make_exception( struct pso_pointer frame_pointer );
 
 struct pso_pointer destroy_exception( struct pso_pointer fp );
 
+struct pso_pointer
+throw_exception( struct pso_pointer location,
+                 struct pso_pointer payload,
+                 struct pso_pointer frame_pointer );
 #endif