C++ ExplodedNode::pred_size方法代码示例

void ExplodedGraph::reclaimRecentlyAllocatedNodes() {
  if (!recentlyAllocatedNodes)
    return;
  NodeList &nl = *getNodeList(recentlyAllocatedNodes);
 
  // Reclaimn all nodes that match *all* the following criteria:
  //
  // (1) 1 predecessor (that has one successor)
  // (2) 1 successor (that has one predecessor)
  // (3) The ProgramPoint is for a PostStmt.
  // (4) There is no 'tag' for the ProgramPoint.
  // (5) The 'store' is the same as the predecessor.
  // (6) The 'GDM' is the same as the predecessor.
  // (7) The LocationContext is the same as the predecessor.
  // (8) The PostStmt is for a non-CFGElement expression.
  
  for (NodeList::iterator i = nl.begin(), e = nl.end() ; i != e; ++i) {
    ExplodedNode *node = *i;
    
    // Conditions 1 and 2.
    if (node->pred_size() != 1 || node->succ_size() != 1)
      continue;

    ExplodedNode *pred = *(node->pred_begin());
    if (pred->succ_size() != 1)
      continue;

    ExplodedNode *succ = *(node->succ_begin());
    if (succ->pred_size() != 1)
      continue;

    // Condition 3.
    ProgramPoint progPoint = node->getLocation();
    if (!isa<PostStmt>(progPoint))
      continue;
    // Condition 4.
    PostStmt ps = cast<PostStmt>(progPoint);
    if (ps.getTag())
      continue;

    if (isa<BinaryOperator>(ps.getStmt()))
      continue;

    // Conditions 5, 6, and 7.
    const ProgramState *state = node->getState();
    const ProgramState *pred_state = pred->getState();    
    if (state->store != pred_state->store || state->GDM != pred_state->GDM ||
        progPoint.getLocationContext() != pred->getLocationContext())
      continue;

    // Condition 8.
    if (node->getCFG().isBlkExpr(ps.getStmt()))
      continue;
    
    // If we reach here, we can remove the node.  This means:
    // (a) changing the predecessors successor to the successor of this node
    // (b) changing the successors predecessor to the predecessor of this node
    // (c) Putting 'node' onto freeNodes.
    pred->replaceSuccessor(succ);
    succ->replacePredecessor(pred);
    if (!freeNodes)
      freeNodes = new NodeList();
    getNodeList(freeNodes)->push_back(node);
    Nodes.RemoveNode(node);
    --NumNodes;
    node->~ExplodedNode();
  }
  
  nl.clear();
}

void ExprEngine::VisitLogicalExpr(const BinaryOperator* B, ExplodedNode *Pred,
                                  ExplodedNodeSet &Dst) {
  assert(B->getOpcode() == BO_LAnd ||
         B->getOpcode() == BO_LOr);

  StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx);
  ProgramStateRef state = Pred->getState();

  ExplodedNode *N = Pred;
  while (!N->getLocation().getAs<BlockEntrance>()) {
    ProgramPoint P = N->getLocation();
    assert(P.getAs<PreStmt>()|| P.getAs<PreStmtPurgeDeadSymbols>());
    (void) P;
    assert(N->pred_size() == 1);
    N = *N->pred_begin();
  }
  assert(N->pred_size() == 1);
  N = *N->pred_begin();
  BlockEdge BE = N->getLocation().castAs<BlockEdge>();
  SVal X;

  // Determine the value of the expression by introspecting how we
  // got this location in the CFG.  This requires looking at the previous
  // block we were in and what kind of control-flow transfer was involved.
  const CFGBlock *SrcBlock = BE.getSrc();
  // The only terminator (if there is one) that makes sense is a logical op.
  CFGTerminator T = SrcBlock->getTerminator();
  if (const BinaryOperator *Term = cast_or_null<BinaryOperator>(T.getStmt())) {
    (void) Term;
    assert(Term->isLogicalOp());
    assert(SrcBlock->succ_size() == 2);
    // Did we take the true or false branch?
    unsigned constant = (*SrcBlock->succ_begin() == BE.getDst()) ? 1 : 0;
    X = svalBuilder.makeIntVal(constant, B->getType());
  }
  else {
    // If there is no terminator, by construction the last statement
    // in SrcBlock is the value of the enclosing expression.
    // However, we still need to constrain that value to be 0 or 1.
    assert(!SrcBlock->empty());
    CFGStmt Elem = SrcBlock->rbegin()->castAs<CFGStmt>();
    const Expr *RHS = cast<Expr>(Elem.getStmt());
    SVal RHSVal = N->getState()->getSVal(RHS, Pred->getLocationContext());

    if (RHSVal.isUndef()) {
      X = RHSVal;
    } else {
      DefinedOrUnknownSVal DefinedRHS = RHSVal.castAs<DefinedOrUnknownSVal>();
      ProgramStateRef StTrue, StFalse;
      llvm::tie(StTrue, StFalse) = N->getState()->assume(DefinedRHS);
      if (StTrue) {
        if (StFalse) {
          // We can't constrain the value to 0 or 1.
          // The best we can do is a cast.
          X = getSValBuilder().evalCast(RHSVal, B->getType(), RHS->getType());
        } else {
          // The value is known to be true.
          X = getSValBuilder().makeIntVal(1, B->getType());
        }
      } else {
        // The value is known to be false.
        assert(StFalse && "Infeasible path!");
        X = getSValBuilder().makeIntVal(0, B->getType());
      }
    }
  }
  Bldr.generateNode(B, Pred, state->BindExpr(B, Pred->getLocationContext(), X));
}

void ExprEngine::VisitLogicalExpr(const BinaryOperator* B, ExplodedNode *Pred,
                                  ExplodedNodeSet &Dst) {
  assert(B->getOpcode() == BO_LAnd ||
         B->getOpcode() == BO_LOr);

  StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx);
  ProgramStateRef state = Pred->getState();

  if (B->getType()->isVectorType()) {
    // FIXME: We do not model vector arithmetic yet. When adding support for
    // that, note that the CFG-based reasoning below does not apply, because
    // logical operators on vectors are not short-circuit. Currently they are
    // modeled as short-circuit in Clang CFG but this is incorrect.
    // Do not set the value for the expression. It'd be UnknownVal by default.
    Bldr.generateNode(B, Pred, state);
    return;
  }

  ExplodedNode *N = Pred;
  while (!N->getLocation().getAs<BlockEntrance>()) {
    ProgramPoint P = N->getLocation();
    assert(P.getAs<PreStmt>()|| P.getAs<PreStmtPurgeDeadSymbols>());
    (void) P;
    assert(N->pred_size() == 1);
    N = *N->pred_begin();
  }
  assert(N->pred_size() == 1);
  N = *N->pred_begin();
  BlockEdge BE = N->getLocation().castAs<BlockEdge>();
  SVal X;

  // Determine the value of the expression by introspecting how we
  // got this location in the CFG.  This requires looking at the previous
  // block we were in and what kind of control-flow transfer was involved.
  const CFGBlock *SrcBlock = BE.getSrc();
  // The only terminator (if there is one) that makes sense is a logical op.
  CFGTerminator T = SrcBlock->getTerminator();
  if (const BinaryOperator *Term = cast_or_null<BinaryOperator>(T.getStmt())) {
    (void) Term;
    assert(Term->isLogicalOp());
    assert(SrcBlock->succ_size() == 2);
    // Did we take the true or false branch?
    unsigned constant = (*SrcBlock->succ_begin() == BE.getDst()) ? 1 : 0;
    X = svalBuilder.makeIntVal(constant, B->getType());
  }
  else {
    // If there is no terminator, by construction the last statement
    // in SrcBlock is the value of the enclosing expression.
    // However, we still need to constrain that value to be 0 or 1.
    assert(!SrcBlock->empty());
    CFGStmt Elem = SrcBlock->rbegin()->castAs<CFGStmt>();
    const Expr *RHS = cast<Expr>(Elem.getStmt());
    SVal RHSVal = N->getState()->getSVal(RHS, Pred->getLocationContext());

    if (RHSVal.isUndef()) {
      X = RHSVal;
    } else {
      // We evaluate "RHSVal != 0" expression which result in 0 if the value is
      // known to be false, 1 if the value is known to be true and a new symbol
      // when the assumption is unknown.
      nonloc::ConcreteInt Zero(getBasicVals().getValue(0, B->getType()));
      X = evalBinOp(N->getState(), BO_NE, 
                    svalBuilder.evalCast(RHSVal, B->getType(), RHS->getType()),
                    Zero, B->getType());
    }
  }
  Bldr.generateNode(B, Pred, state->BindExpr(B, Pred->getLocationContext(), X));
}