vm: use C++ exceptions instead of longjmp(), to make Windows crash more

vm/collector.hpp

@@ -1,6 +1,8 @@
 namespace factor
 {
 
+struct must_start_gc_again {};
+
 template<typename TargetGeneration, typename Policy> struct data_workhorse {
 	factor_vm *parent;
 	TargetGeneration *target;
@@ -27,8 +29,7 @@ template<typename TargetGeneration, typename Policy> struct data_workhorse {
 	{
 		cell size = untagged->size();
 		object *newpointer = target->allot(size);
-		/* XXX not exception-safe */
-		if(!newpointer) longjmp(parent->current_gc->gc_unwind,1);
+		if(!newpointer) throw must_start_gc_again();
 
 		memcpy(newpointer,untagged,size);
 		untagged->forward_to(newpointer);

vm/gc.cpp

@@ -135,12 +135,10 @@ void factor_vm::gc(gc_op op, cell requested_bytes, bool trace_contexts_p)
 
 	/* Keep trying to GC higher and higher generations until we don't run out
 	of space */
-	if(setjmp(current_gc->gc_unwind))
+	for(;;)
+	{
+		try
 		{
-		/* We come back here if a generation is full */
-		start_gc_again();
-	}
-
 			current_gc->event->op = current_gc->op;
 
 			switch(current_gc->op)
@@ -180,6 +178,16 @@ void factor_vm::gc(gc_op op, cell requested_bytes, bool trace_contexts_p)
 				break;
 			}
 
+			break;
+		}
+		catch(const must_start_gc_again e)
+		{
+			/* We come back here if a generation is full */
+			start_gc_again();
+			continue;
+		}
+	}
+
 	end_gc();
 
 	delete current_gc;

vm/gc.hpp

@@ -45,7 +45,6 @@ struct gc_event {
 struct gc_state {
 	gc_op op;
 	u64 start_time;
-	jmp_buf gc_unwind;
 	gc_event *event;
 
 	explicit gc_state(gc_op op_, factor_vm *parent);

vm/master.hpp

@@ -16,7 +16,6 @@
 #include <fcntl.h>
 #include <limits.h>
 #include <math.h>
-#include <setjmp.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>