NullDerefAndRedundantComparisonCollector


1   /*
2    * Bytecode analysis framework
3    * Copyright (C) 2005, University of Maryland
4    * 
5    * This library is free software; you can redistribute it and/or
6    * modify it under the terms of the GNU Lesser General Public
7    * License as published by the Free Software Foundation; either
8    * version 2.1 of the License, or (at your option) any later version.
9    * 
10   * This library is distributed in the hope that it will be useful,
11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   * Lesser General Public License for more details.
14   * 
15   * You should have received a copy of the GNU Lesser General Public
16   * License along with this library; if not, write to the Free Software
17   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18   */
19  
20  package edu.umd.cs.findbugs.ba.npe;
21  
22  import java.util.BitSet  ;
23  import java.util.Set  ;
24  import java.util.SortedSet  ;
25  
26  import edu.umd.cs.findbugs.ba.ClassContext;
27  import edu.umd.cs.findbugs.ba.Location;
28  import edu.umd.cs.findbugs.ba.vna.ValueNumber;
29  import edu.umd.cs.findbugs.ba.vna.ValueNumberDataflow;
30  import edu.umd.cs.findbugs.ba.vna.ValueNumberFrame;
31  
32  /**
33   * Callback interface for collecting null pointer derefs and
34   * redundant null comparisons.
35   * 
36   * @see edu.umd.cs.findbugs.ba.npe.NullDerefAndRedundantComparisonFinder
37   * @author David Hovemeyer
38   */
39  public interface NullDerefAndRedundantComparisonCollector {
40      /**
41       * Subclasses should override this method to capture locations where
42       * a null pointer is dereferenced.
43       * @param classContext TODO
44       * @param location    the Location of the null dereference
45       * @param valueNumber the ValueNumber of the possibly-null value
46       * @param refValue    the kind of possibly-null value dereferenced
47       * @param vnaFrame    The ValueNumber Frame at the point where the dereference occurred
48       */
49      public void foundNullDeref(ClassContext classContext, Location location, ValueNumber valueNumber, IsNullValue refValue, ValueNumberFrame vnaFrame);
50  
51      /**
52       * Subclasses should override this method to capture locations where
53       * a redundant null comparision is performed.
54       * 
55       * @param location        the Location of the redundant null check
56       * @param redundantBranch the RedundantBranch
57       */
58      public void foundRedundantNullCheck(Location location, RedundantBranch redundantBranch);
59      
60      /**
61       * Subclasses should override this method to capture values
62       * assigned null (or that become null through a comparison and branch)
63       * that are guaranteed to reach a dereference (ignoring
64       * implicit exception paths).
65       * @param derefLocationSet     set of locations where dereferences occur
66       * @param doomedLocations TODO
67       * @param vna TODO
68       * @param refValue             the null value
69       * @param alwaysOnExceptionPath true if the location(s) where the value was observed
70       *                               to be null and unconditionally dereferenced were
71       *                               all on exception paths
72       * @param npeIfStatementCovered TODO
73       * @param assignedNullLocationSet set of locations where the value becomes null
74       */
75      public void foundGuaranteedNullDeref(
76              Set  <Location> assignedNullLocationSet,
77              Set  <Location> derefLocationSet,
78              SortedSet  <Location> doomedLocations,
79              ValueNumberDataflow vna,
80              ValueNumber refValue,
81              boolean alwaysOnExceptionPath,
82              boolean npeIfStatementCovered);
83  }
84
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