From bfa6572a30b82fb1a430cb78e79a55ed93e4640a Mon Sep 17 00:00:00 2001
From: bdemsky <bdemsky>
Date: Mon, 25 Oct 2004 15:52:42 +0000
Subject: [PATCH] Had a bug in our implementation.  If the list empties when
 the tail is at the last position in a ListNode, the tail gets zeroed.  This
 should never happen.

---
 Repair/RepairCompiler/MCC/Runtime/SimpleHash.cc | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/Repair/RepairCompiler/MCC/Runtime/SimpleHash.cc b/Repair/RepairCompiler/MCC/Runtime/SimpleHash.cc
index 07f8a12..6281d15 100755
--- a/Repair/RepairCompiler/MCC/Runtime/SimpleHash.cc
+++ b/Repair/RepairCompiler/MCC/Runtime/SimpleHash.cc
@@ -119,10 +119,12 @@ void WorkList::pop() {
   int newoffset=tailoffset+4;
   struct ListNode *ptr=tail;
   if (newoffset>=WLISTSIZE) {
-    newoffset-=WLISTSIZE;
-    struct ListNode *oldptr=ptr;
-    ptr=ptr->next;
-    free(oldptr);
+    if (newoffset!=WLISTSIZE||head!=tail) {
+      newoffset-=WLISTSIZE;
+      struct ListNode *oldptr=ptr;
+      ptr=ptr->next;
+      free(oldptr);
+    }
   }
   tail=ptr;
   tailoffset=newoffset;
@@ -136,6 +138,10 @@ void WorkList::add(int id,int type, int lvalue, int rvalue) {
     }
     headoffset=0;
     head=head->next;
+    if (tailoffset==WLISTSIZE) { /* roll the tail over also */
+      tailoffset=0;
+      tail=tail->next;
+    }
   }
   head->data[headoffset++]=id;
   head->data[headoffset++]=type;
-- 
2.34.1