From 02eb24cd577ddc1ee624b2001acb7b04ad2c419e Mon Sep 17 00:00:00 2001
From: Mark Thom <markjordanthom@gmail.com>
Date: Sun, 12 Apr 2020 23:33:07 -0600
Subject: [PATCH] correct partial string copying by resetting threshold to
 redirected partial string stubs to 0

---
 src/prolog/machine/copier.rs |  2 +-
 src/prolog/machine/stack.rs  | 14 ++++++++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/prolog/machine/copier.rs b/src/prolog/machine/copier.rs
index baa1f2b9..c5a3ef18 100644
--- a/src/prolog/machine/copier.rs
+++ b/src/prolog/machine/copier.rs
@@ -104,7 +104,7 @@ impl<T: CopierTarget> CopyTermState<T> {
     fn copy_partial_string(&mut self, addr: usize, n: usize) {
         if let &HeapCellValue::Addr(Addr::PStrLocation(h, _)) = &self.target[addr] {
             if h >= self.old_h {
-                *self.value_at_scan() = HeapCellValue::Addr(Addr::PStrLocation(h, n));
+                *self.value_at_scan() = HeapCellValue::Addr(Addr::PStrLocation(h, 0));
                 self.scan += 1;
 
                 return;
diff --git a/src/prolog/machine/stack.rs b/src/prolog/machine/stack.rs
index e2602e72..4468899c 100644
--- a/src/prolog/machine/stack.rs
+++ b/src/prolog/machine/stack.rs
@@ -165,16 +165,19 @@ impl Stack {
 
         unsafe {
             let new_top = self.buf.new_block(frame_size);
+            let e = self.buf.top as usize - self.buf.base as usize;
 
             for idx in 0 .. num_cells {
                 let offset = prelude_size::<AndFramePrelude>() + idx * mem::size_of::<Addr>();
-                ptr::write((self.buf.top as usize + offset) as *mut Addr, Addr::StackCell(0,0));
+                ptr::write(
+                    (self.buf.top as usize + offset) as *mut Addr,
+                    Addr::StackCell(e, idx + 1),
+                );
             }
 
             let and_frame = &mut *(self.buf.top as *mut AndFrame);
             and_frame.prelude.univ_prelude.num_cells = num_cells;
 
-            let e = self.buf.top as usize - self.buf.base as usize;
             self.buf.top = new_top;
 
             e
@@ -186,16 +189,19 @@ impl Stack {
 
         unsafe {
             let new_top = self.buf.new_block(frame_size);
+            let b = self.buf.top as usize - self.buf.base as usize;
 
             for idx in 0 .. num_cells {
                 let offset = prelude_size::<OrFramePrelude>() + idx * mem::size_of::<Addr>();
-                ptr::write((self.buf.top as usize + offset) as *mut Addr, Addr::StackCell(0,0));
+                ptr::write(
+                    (self.buf.top as usize + offset) as *mut Addr,
+                    Addr::StackCell(b, idx),
+                );
             }
 
             let or_frame = &mut *(self.buf.top as *mut OrFrame);
             or_frame.prelude.univ_prelude.num_cells = num_cells;
 
-            let b = self.buf.top as usize - self.buf.base as usize;
             self.buf.top = new_top;
 
             b
-- 
2.54.0