From: Mark Thom <markjordanthom@gmail.com>
Date: Fri, 12 Jun 2020 03:25:20 +0000 (-0600)
Subject: adjust the tail created by CreatePartialString to point to the last cell it pushed... 
X-Git-Tag: v0.8.127~42
X-Git-Url: https://git.sagredo.dev/?a=commitdiff_plain;h=d9de38b9359facf3babfe54a512399d3cb78cc5e;p=scryer-prolog.git

adjust the tail created by CreatePartialString to point to the last cell it pushed to the heap (#586)
---

diff --git a/src/prolog/machine/system_calls.rs b/src/prolog/machine/system_calls.rs
index d4607c59..3c50c079 100644
--- a/src/prolog/machine/system_calls.rs
+++ b/src/prolog/machine/system_calls.rs
@@ -1079,19 +1079,18 @@ impl MachineState {
                     }
                 };
 
-                let h = self.heap.h();
-
                 if atom.as_str().is_empty() {
                     self.fail = true;
                     return Ok(());
                 }
 
                 let pstr = self.heap.allocate_pstr(atom.as_str());
-                let pstr_tail = self.heap[h + 1].as_addr(h + 1);
-
                 self.unify(self[temp_v!(2)], pstr);
 
                 if !self.fail {
+                    let h = self.heap.h();
+                    let pstr_tail = self.heap[h - 1].as_addr(h - 1);
+
                     self.unify(self[temp_v!(3)], pstr_tail);
                 }
             }