Corrected a long-standing crash condition that happens when a

generated cell is modified multiple times.  If the original cell
is orphaned (no longer used anywhere in the design), it is deleted.
However, an instance of the cell may exist in the secondary
select buffer if the cell was previously moved or copied, and
an attempt to do another move or copy will clear the secondary
select buffer, encounter the deleted cell, and crash the program.

VERSION

@@ -1 +1 @@
-8.3.501
+8.3.502

database/DBcellname.c

@@ -224,7 +224,7 @@ DBCellDelete(cellname, force)
 {
     HashEntry *entry;
     CellDef *celldef;
-    CellUse *celluse;
+    CellUse *celluse, *lastuse;
     bool result;
 
     entry = HashLookOnly(&dbCellDefTable, cellname);
@@ -259,6 +259,29 @@ DBCellDelete(cellname, force)
 	return FALSE;
     }
 
+    /* 2nd pass:  If there are instances of the cell in		*/
+    /* internal	cells like SelectDef, etc., then remove the use	*/
+    /* from the definition.					*/
+
+    lastuse = NULL;
+    celluse = celldef->cd_parents;
+    while (celluse != (CellUse *) NULL)
+    {
+	if (celluse->cu_parent != (CellDef *)NULL)
+	{
+	    if ((celluse->cu_parent->cd_flags & CDINTERNAL) == CDINTERNAL)
+	    {
+		DBDeleteCell(celluse);
+		celluse = lastuse;
+	    }
+	}
+	lastuse = celluse;
+	if (lastuse == NULL)
+	    celluse = celldef->cd_parents;
+	else
+	    celluse = celluse->cu_nextuse;
+    }
+
     /* Cleared to delete. . . now prompt user if the cell has changes. */
     /* Last chance to save! */