return to toplevel from a long running query after receiving Ctrl-C

src/prolog/machine/machine_state_impl.rs

@@ -8,6 +8,7 @@ use prolog::forms::*;
 use prolog::heap_iter::*;
 use prolog::heap_print::*;
 use prolog::instructions::*;
+use prolog::machine::INTERRUPT;
 use prolog::machine::and_stack::*;
 use prolog::machine::attributed_variables::*;
 use prolog::machine::code_repo::CodeRepo;
@@ -3176,6 +3177,13 @@ impl MachineState {
         lco: bool,
         use_default_cp: bool,
     ) {
+	let interrupted = INTERRUPT.load(std::sync::atomic::Ordering::Relaxed);
+
+	if INTERRUPT.compare_and_swap(interrupted, false, std::sync::atomic::Ordering::Relaxed) {
+	    self.fail = true;
+	    return;
+	}
+	
         let mut default_call_policy: Box<CallPolicy> = Box::new(DefaultCallPolicy {});
         let call_policy = if use_default_cp {
             &mut default_call_policy

src/prolog/machine/mod.rs

@@ -46,6 +46,7 @@ use std::io::{stdout, Read, Write};
 use std::mem;
 use std::ops::Index;
 use std::rc::Rc;
+use std::sync::atomic::AtomicBool;
 
 use termion::raw::IntoRawMode;
 
@@ -54,6 +55,10 @@ pub struct MachinePolicies {
     cut_policy: Box<CutPolicy>,
 }
 
+lazy_static! {
+    pub static ref INTERRUPT: AtomicBool = AtomicBool::new(false);
+}
+
 impl MachinePolicies {
     #[inline]
     fn new() -> Self {