Berry fix reference when exeception is raised

lib/libesp32/berry/src/be_exec.c

@@ -61,6 +61,7 @@ struct pcall {
 
 struct vmstate {
     int top, reg, depth;
+    int refcount;
 };
 
 struct strbuf {
@@ -125,6 +126,7 @@ static void vm_state_save(bvm *vm, struct vmstate *state)
     state->depth = be_stack_count(&vm->callstack);
     state->top = cast_int(vm->top - vm->stack);
     state->reg = cast_int(vm->reg - vm->stack);
+    state->refcount = vm->refstack.count;
 }
 
 static void copy_exception(bvm *vm, int res, int dstindex)
@@ -143,6 +145,7 @@ static void copy_exception(bvm *vm, int res, int dstindex)
 static void vm_state_restore(bvm *vm, const struct vmstate *state, int res)
 {
     vm->reg = vm->stack + state->reg;
+    be_vector_resize(vm, &vm->refstack, state->refcount);
     /* copy exception information to top */
     copy_exception(vm, res, state->top);
     be_assert(be_stack_count(&vm->callstack) >= state->depth);
@@ -444,6 +447,7 @@ void be_except_block_setup(bvm *vm)
     /* set longjmp() jump point */
     frame->errjmp.status = 0;
     frame->errjmp.prev = vm->errjmp; /* save long jump list */
+    frame->refcount = vm->refstack.count; /* save reference pointer */
     vm->errjmp = &frame->errjmp;
     fixup_exceptstack(vm, lbase);
 }
@@ -455,6 +459,7 @@ void be_except_block_resume(bvm *vm)
     struct bexecptframe *frame = be_stack_top(&vm->exceptstack);
     if (errorcode == BE_EXCEPTION) {
         vm->errjmp = vm->errjmp->prev;
+        be_vector_resize(vm, &vm->refstack, frame->refcount);
         /* jump to except instruction */
         vm->ip = frame->ip + IGET_sBx(frame->ip[-1]);
         if (be_stack_count(&vm->callstack) > frame->depth) {

lib/libesp32/berry/src/be_exec.h

@@ -45,6 +45,7 @@ struct bexecptframe {
     struct blongjmp errjmp; /* long jump information */
     int depth; /* function call stack depth */
     binstruction *ip; /* instruction pointer */
+    int refcount; /* save object reference stack */
 };
 
 void be_throw(bvm *vm, int errorcode);

lib/libesp32/berry/tests/reference.be

@@ -0,0 +1,31 @@
+# try to exercise bug in reference
+
+class failable
+    var fail        # if 'true', tostring() raises an exception
+
+    def tostring()
+        if self.fail
+            raise "internal_error", "FAIL"
+            return "FAIL"
+        else
+            return "SUCCESS"
+        end
+    end
+end
+f = failable()
+
+l1 = [1, 2, f]
+l2 = ["foo", l1]
+l1.push(l1)
+
+assert(str(l2) == "['foo', [1, 2, SUCCESS, [...]]]")
+assert(str(l1) == "[1, 2, SUCCESS, [...]]")
+
+f.fail = true
+try
+    print(str(l1))
+except ..
+end
+
+f.fail = false
+assert(str(l1) == "[1, 2, SUCCESS, [...]]")  # FAILS