handle TCO when setting up verify_attributes interrupts

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "scryer-prolog"
-version = "0.8.107"
+version = "0.8.108"
 authors = ["Mark Thom <markjordanthom@gmail.com>"]
 build = "build.rs"
 repository = "https://github.com/mthom/scryer-prolog"

src/prolog/machine/attributed_variables.rs

@@ -40,7 +40,12 @@ impl AttrVarInitializer {
 impl MachineState {
     pub(super) fn push_attr_var_binding(&mut self, h: usize, addr: Addr) {
         if self.attr_var_init.bindings.is_empty() {
-            self.attr_var_init.cp = self.p.local();
+            if self.last_call {
+                self.attr_var_init.cp = self.cp;
+            } else {
+                self.attr_var_init.cp = self.p.local();
+            }
+            
             self.p = CodePtr::VerifyAttrInterrupt(self.attr_var_init.verify_attrs_loc);
         }
 

src/prolog/machine/mod.rs

@@ -1046,7 +1046,7 @@ impl MachineState {
 
             match self.p {
                 CodePtr::VerifyAttrInterrupt(_) => {
-                    self.p = CodePtr::Local(self.attr_var_init.cp);// + 1);
+                    self.p = CodePtr::Local(self.attr_var_init.cp);
 
                     if !self.verify_attr_stepper(indices, policies, code_repo, prolog_stream) {
                         if self.fail {