Re: [patch, libfortran] Fix PR 54736, memory corruption with GFORTRAN_CONVERT_UNIT

[Thomas Koenig]

Hello world,

the previous version of the patch has an issue that Shane pointed
out in the PR.  This version should work; at least it survived
all the test cases I could come up with.

Regression-tested (again).  OK for trunk?  Also for 4.6 and 4.7?

        Thomas

2012-10-01  Thomas König  <tkoe...@gcc.gnu.org>

        PR libfortran/54736
        * runtime/environ.c (search_unit):  Correct logic
        for binary search.
        (mark_single):  Fix index errors.


Index: runtime/environ.c
===================================================================
--- runtime/environ.c	(Revision 191857)
+++ runtime/environ.c	(Arbeitskopie)
@@ -459,21 +459,35 @@ search_unit (int unit, int *ip)
 {
   int low, high, mid;
 
-  low = -1;
-  high = n_elist;
-  while (high - low > 1)
+  if (n_elist == 0)
     {
+      *ip = 0;
+      return 0;
+    }
+
+  low = 0;
+  high = n_elist - 1;
+
+  do 
+    {
       mid = (low + high) / 2;
-      if (unit <= elist[mid].unit)
-	high = mid;
+      if (unit == elist[mid].unit)
+	{
+	  *ip = mid;
+	  return 1;
+	}
+      else if (unit > elist[mid].unit)
+	low = mid + 1;
       else
-	low = mid;
-    }
-  *ip = high;
-  if (elist[high].unit == unit)
-    return 1;
+	high = mid - 1;
+    } while (low <= high);
+
+  if (unit > elist[mid].unit)
+    *ip = mid + 1;
   else
-    return 0;
+    *ip = mid;
+
+  return 0;
 }
 
 /* This matches a keyword.  If it is found, return the token supplied,
@@ -588,13 +602,13 @@ mark_single (int unit)
     }
   if (search_unit (unit, &i))
     {
-      elist[unit].conv = endian;
+      elist[i].conv = endian;
     }
   else
     {
-      for (j=n_elist; j>=i; j--)
+      for (j=n_elist-1; j>=i; j--)
 	elist[j+1] = elist[j];
-    
+
       n_elist += 1;
       elist[i].unit = unit;
       elist[i].conv = endian;