lib/StaticAnalyzer/Checkers/SimpleStreamChecker.cpp - clang - Git at Google

 //===-- SimpleStreamChecker.cpp -----------------------------------------*- C++ -*--//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // Defines a checker for proper use of fopen/fclose APIs.
 //   - If a file has been closed with fclose, it should not be accessed again.
 //   Accessing a closed file results in undefined behavior.
 //   - If a file was opened with fopen, it must be closed with fclose before
 //   the execution ends. Failing to do so results in a resource leak.
 //
 //===----------------------------------------------------------------------===//

 #include "ClangSACheckers.h"
 #include "clang/StaticAnalyzer/Core/Checker.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"

 using namespace clang;
 using namespace ento;

 namespace {
 typedef llvm::SmallVector<SymbolRef, 2> SymbolVector;

 struct StreamState {
 private:
   enum Kind { Opened, Closed } K;
   StreamState(Kind InK) : K(InK) { }

 public:
   bool isOpened() const { return K == Opened; }
   bool isClosed() const { return K == Closed; }

   static StreamState getOpened() { return StreamState(Opened); }
   static StreamState getClosed() { return StreamState(Closed); }

   bool operator==(const StreamState &X) const {
     return K == X.K;
   }
   void Profile(llvm::FoldingSetNodeID &ID) const {
     ID.AddInteger(K);
   }
 };

 class SimpleStreamChecker : public Checker<check::PostCall,
                                            check::PreCall,
                                            check::DeadSymbols,
                                            check::Bind,
                                            check::RegionChanges> {

   mutable IdentifierInfo *IIfopen, *IIfclose;

   OwningPtr<BugType> DoubleCloseBugType;
   OwningPtr<BugType> LeakBugType;

   void initIdentifierInfo(ASTContext &Ctx) const;

   void reportDoubleClose(SymbolRef FileDescSym,
                          const CallEvent &Call,
                          CheckerContext &C) const;

   void reportLeaks(SymbolVector LeakedStreams,
                    CheckerContext &C,
                    ExplodedNode *ErrNode) const;

   bool guaranteedNotToCloseFile(const CallEvent &Call) const;

 public:
   SimpleStreamChecker();

   /// Process fopen.
   void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
   /// Process fclose.
   void checkPreCall(const CallEvent &Call, CheckerContext &C) const;

   void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;

   /// Deal with symbol escape as a byproduct of a bind.
   void checkBind(SVal location, SVal val, const Stmt*S,
                  CheckerContext &C) const;

   /// Deal with symbol escape as a byproduct of a region change.
   ProgramStateRef
   checkRegionChanges(ProgramStateRef state,
                      const StoreManager::InvalidatedSymbols *invalidated,
                      ArrayRef<const MemRegion *> ExplicitRegions,
                      ArrayRef<const MemRegion *> Regions,
                      const CallEvent *Call) const;
   bool wantsRegionChangeUpdate(ProgramStateRef state) const {
     return true;
   }
 };

 } // end anonymous namespace

 /// The state of the checker is a map from tracked stream symbols to their
 /// state. Let's store it in the ProgramState.
 REGISTER_MAP_WITH_PROGRAMSTATE(StreamMap, SymbolRef, StreamState)

 namespace {
 class StopTrackingCallback : public SymbolVisitor {
   ProgramStateRef state;
 public:
   StopTrackingCallback(ProgramStateRef st) : state(st) {}
   ProgramStateRef getState() const { return state; }

   bool VisitSymbol(SymbolRef sym) {
     state = state->remove<StreamMap>(sym);
     return true;
   }
 };
 } // end anonymous namespace


 SimpleStreamChecker::SimpleStreamChecker() : IIfopen(0), IIfclose(0) {
   // Initialize the bug types.
   DoubleCloseBugType.reset(new BugType("Double fclose",
                                        "Unix Stream API Error"));

   LeakBugType.reset(new BugType("Resource Leak",
                                 "Unix Stream API Error"));
   // Sinks are higher importance bugs as well as calls to assert() or exit(0).
   LeakBugType->setSuppressOnSink(true);
 }

 void SimpleStreamChecker::checkPostCall(const CallEvent &Call,
                                         CheckerContext &C) const {
   initIdentifierInfo(C.getASTContext());

   if (!Call.isGlobalCFunction())
     return;

   if (Call.getCalleeIdentifier() != IIfopen)
     return;

   // Get the symbolic value corresponding to the file handle.
   SymbolRef FileDesc = Call.getReturnValue().getAsSymbol();
   if (!FileDesc)
     return;

   // Generate the next transition (an edge in the exploded graph).
   ProgramStateRef State = C.getState();
   State = State->set<StreamMap>(FileDesc, StreamState::getOpened());
   C.addTransition(State);
 }

 void SimpleStreamChecker::checkPreCall(const CallEvent &Call,
                                        CheckerContext &C) const {
   initIdentifierInfo(C.getASTContext());

   if (!Call.isGlobalCFunction())
     return;

   if (Call.getCalleeIdentifier() != IIfclose)
     return;

   if (Call.getNumArgs() != 1)
     return;

   // Get the symbolic value corresponding to the file handle.
   SymbolRef FileDesc = Call.getArgSVal(0).getAsSymbol();
   if (!FileDesc)
     return;

   // Check if the stream has already been closed.
   ProgramStateRef State = C.getState();
   const StreamState *SS = State->get<StreamMap>(FileDesc);
   if (SS && SS->isClosed()) {
     reportDoubleClose(FileDesc, Call, C);
     return;
   }

   // Generate the next transition, in which the stream is closed.
   State = State->set<StreamMap>(FileDesc, StreamState::getClosed());
   C.addTransition(State);
 }

 static bool isLeaked(SymbolRef Sym, const StreamState &SS,
                      bool IsSymDead, ProgramStateRef State) {
   if (IsSymDead && SS.isOpened()) {
     // If a symbol is NULL, assume that fopen failed on this path.
     // A symbol should only be considered leaked if it is non-null.
     ConstraintManager &CMgr = State->getConstraintManager();
     ConditionTruthVal OpenFailed = CMgr.isNull(State, Sym);
     return !OpenFailed.isConstrainedTrue();
   }
   return false;
 }

 void SimpleStreamChecker::checkDeadSymbols(SymbolReaper &SymReaper,
                                            CheckerContext &C) const {
   ProgramStateRef State = C.getState();
   SymbolVector LeakedStreams;
   StreamMapTy TrackedStreams = State->get<StreamMap>();
   for (StreamMapTy::iterator I = TrackedStreams.begin(),
                              E = TrackedStreams.end(); I != E; ++I) {
     SymbolRef Sym = I->first;
     bool IsSymDead = SymReaper.isDead(Sym);

     // Collect leaked symbols.
     if (isLeaked(Sym, I->second, IsSymDead, State))
       LeakedStreams.push_back(Sym);

     // Remove the dead symbol from the streams map.
     if (IsSymDead)
       State = State->remove<StreamMap>(Sym);
   }

   ExplodedNode *N = C.addTransition(State);
   reportLeaks(LeakedStreams, C, N);
 }

 void SimpleStreamChecker::reportDoubleClose(SymbolRef FileDescSym,
                                             const CallEvent &Call,
                                             CheckerContext &C) const {
   // We reached a bug, stop exploring the path here by generating a sink.
   ExplodedNode *ErrNode = C.generateSink();
   // If we've already reached this node on another path, return.
   if (!ErrNode)
     return;

   // Generate the report.
   BugReport *R = new BugReport(*DoubleCloseBugType,
       "Closing a previously closed file stream", ErrNode);
   R->addRange(Call.getSourceRange());
   R->markInteresting(FileDescSym);
   C.emitReport(R);
 }

 void SimpleStreamChecker::reportLeaks(SymbolVector LeakedStreams,
                                                CheckerContext &C,
                                                ExplodedNode *ErrNode) const {
   // Attach bug reports to the leak node.
   // TODO: Identify the leaked file descriptor.
   for (llvm::SmallVector<SymbolRef, 2>::iterator
       I = LeakedStreams.begin(), E = LeakedStreams.end(); I != E; ++I) {
     BugReport *R = new BugReport(*LeakBugType,
         "Opened file is never closed; potential resource leak", ErrNode);
     R->markInteresting(*I);
     C.emitReport(R);
   }
 }

 // Check various ways a symbol can be invalidated.
 // Stop tracking symbols when a value escapes as a result of checkBind.
 // A value escapes in three possible cases:
 // (1) We are binding to something that is not a memory region.
 // (2) We are binding to a MemRegion that does not have stack storage
 // (3) We are binding to a MemRegion with stack storage that the store
 //     does not understand.
 void SimpleStreamChecker::checkBind(SVal loc, SVal val, const Stmt *S,
                                     CheckerContext &C) const {
   // Are we storing to something that causes the value to "escape"?
   bool escapes = true;
   ProgramStateRef state = C.getState();

   if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
     escapes = !regionLoc->getRegion()->hasStackStorage();

     if (!escapes) {
       // To test (3), generate a new state with the binding added.  If it is
       // the same state, then it escapes (since the store cannot represent
       // the binding). Do this only if we know that the store is not supposed
       // to generate the same state.
       SVal StoredVal = state->getSVal(regionLoc->getRegion());
       if (StoredVal != val)
         escapes = (state == (state->bindLoc(*regionLoc, val)));
     }
   }

   // If our store can represent the binding and we aren't storing to something
   // that doesn't have local storage then just return the state and
   // continue as is.
   if (!escapes)
     return;

   // Otherwise, find all symbols referenced by 'val' that we are tracking
   // and stop tracking them.
   state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
   C.addTransition(state);
 }

 bool SimpleStreamChecker::guaranteedNotToCloseFile(const CallEvent &Call) const{
   // If it's not in a system header, assume it might close a file.
   if (!Call.isInSystemHeader())
     return false;

   // Handle cases where we know a buffer's /address/ can escape.
   if (Call.argumentsMayEscape())
     return false;

   // Note, even though fclose closes the file, we do not list it here
   // since the checker is modeling the call.

   return true;
 }

 // If the symbol we are tracking is invalidated, do not track the symbol as
 // we cannot reason about it anymore.
 ProgramStateRef
 SimpleStreamChecker::checkRegionChanges(ProgramStateRef State,
     const StoreManager::InvalidatedSymbols *invalidated,
     ArrayRef<const MemRegion *> ExplicitRegions,
     ArrayRef<const MemRegion *> Regions,
     const CallEvent *Call) const {

   if (!invalidated || invalidated->empty())
     return State;

   // If it's a call which might close the file, we assume that all regions
   // (explicit and implicit) escaped. Otherwise, whitelist explicit pointers
   // (the parameters to the call); we still can track them.
   llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
   if (!Call || guaranteedNotToCloseFile(*Call)) {
     for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
         E = ExplicitRegions.end(); I != E; ++I) {
       if (const SymbolicRegion *R = (*I)->StripCasts()->getAs<SymbolicRegion>())
         WhitelistedSymbols.insert(R->getSymbol());
     }
   }

   for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
        E = invalidated->end(); I!=E; ++I) {
     SymbolRef sym = *I;
     if (WhitelistedSymbols.count(sym))
       continue;
     // The symbol escaped. Optimistically, assume that the corresponding file
     // handle will be closed somewhere else.
     State = State->remove<StreamMap>(sym);
   }
   return State;
 }

 void SimpleStreamChecker::initIdentifierInfo(ASTContext &Ctx) const {
   if (IIfopen)
     return;
   IIfopen = &Ctx.Idents.get("fopen");
   IIfclose = &Ctx.Idents.get("fclose");
 }

 void ento::registerSimpleStreamChecker(CheckerManager &mgr) {
   mgr.registerChecker<SimpleStreamChecker>();
 }
	//===-- SimpleStreamChecker.cpp ------------------------------------------ C++ ---//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// Defines a checker for proper use of fopen/fclose APIs.
	// - If a file has been closed with fclose, it should not be accessed again.
	// Accessing a closed file results in undefined behavior.
	// - If a file was opened with fopen, it must be closed with fclose before
	// the execution ends. Failing to do so results in a resource leak.
	//
	//===----------------------------------------------------------------------===//

	#include "ClangSACheckers.h"
	#include "clang/StaticAnalyzer/Core/Checker.h"
	#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
	#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
	#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"

	using namespace clang;
	using namespace ento;

	namespace {
	typedef llvm::SmallVector<SymbolRef, 2> SymbolVector;

	struct StreamState {
	private:
	enum Kind { Opened, Closed } K;
	StreamState(Kind InK) : K(InK) { }

	public:
	bool isOpened() const { return K == Opened; }
	bool isClosed() const { return K == Closed; }

	static StreamState getOpened() { return StreamState(Opened); }
	static StreamState getClosed() { return StreamState(Closed); }

	bool operator==(const StreamState &X) const {
	return K == X.K;
	}
	void Profile(llvm::FoldingSetNodeID &ID) const {
	ID.AddInteger(K);
	}
	};

	class SimpleStreamChecker : public Checker<check::PostCall,
	check::PreCall,
	check::DeadSymbols,
	check::Bind,
	check::RegionChanges> {

	mutable IdentifierInfo IIfopen, IIfclose;

	OwningPtr<BugType> DoubleCloseBugType;
	OwningPtr<BugType> LeakBugType;

	void initIdentifierInfo(ASTContext &Ctx) const;

	void reportDoubleClose(SymbolRef FileDescSym,
	const CallEvent &Call,
	CheckerContext &C) const;

	void reportLeaks(SymbolVector LeakedStreams,
	CheckerContext &C,
	ExplodedNode *ErrNode) const;

	bool guaranteedNotToCloseFile(const CallEvent &Call) const;

	public:
	SimpleStreamChecker();

	/// Process fopen.
	void checkPostCall(const CallEvent &Call, CheckerContext &C) const;
	/// Process fclose.
	void checkPreCall(const CallEvent &Call, CheckerContext &C) const;

	void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;

	/// Deal with symbol escape as a byproduct of a bind.
	void checkBind(SVal location, SVal val, const Stmt*S,
	CheckerContext &C) const;

	/// Deal with symbol escape as a byproduct of a region change.
	ProgramStateRef
	checkRegionChanges(ProgramStateRef state,
	const StoreManager::InvalidatedSymbols *invalidated,
	ArrayRef<const MemRegion *> ExplicitRegions,
	ArrayRef<const MemRegion *> Regions,
	const CallEvent *Call) const;
	bool wantsRegionChangeUpdate(ProgramStateRef state) const {
	return true;
	}
	};

	} // end anonymous namespace

	/// The state of the checker is a map from tracked stream symbols to their
	/// state. Let's store it in the ProgramState.
	REGISTER_MAP_WITH_PROGRAMSTATE(StreamMap, SymbolRef, StreamState)

	namespace {
	class StopTrackingCallback : public SymbolVisitor {
	ProgramStateRef state;
	public:
	StopTrackingCallback(ProgramStateRef st) : state(st) {}
	ProgramStateRef getState() const { return state; }

	bool VisitSymbol(SymbolRef sym) {
	state = state->remove<StreamMap>(sym);
	return true;
	}
	};
	} // end anonymous namespace


	SimpleStreamChecker::SimpleStreamChecker() : IIfopen(0), IIfclose(0) {
	// Initialize the bug types.
	DoubleCloseBugType.reset(new BugType("Double fclose",
	"Unix Stream API Error"));

	LeakBugType.reset(new BugType("Resource Leak",
	"Unix Stream API Error"));
	// Sinks are higher importance bugs as well as calls to assert() or exit(0).
	LeakBugType->setSuppressOnSink(true);
	}

	void SimpleStreamChecker::checkPostCall(const CallEvent &Call,
	CheckerContext &C) const {
	initIdentifierInfo(C.getASTContext());

	if (!Call.isGlobalCFunction())
	return;

	if (Call.getCalleeIdentifier() != IIfopen)
	return;

	// Get the symbolic value corresponding to the file handle.
	SymbolRef FileDesc = Call.getReturnValue().getAsSymbol();
	if (!FileDesc)
	return;

	// Generate the next transition (an edge in the exploded graph).
	ProgramStateRef State = C.getState();
	State = State->set<StreamMap>(FileDesc, StreamState::getOpened());
	C.addTransition(State);
	}

	void SimpleStreamChecker::checkPreCall(const CallEvent &Call,
	CheckerContext &C) const {
	initIdentifierInfo(C.getASTContext());

	if (!Call.isGlobalCFunction())
	return;

	if (Call.getCalleeIdentifier() != IIfclose)
	return;

	if (Call.getNumArgs() != 1)
	return;

	// Get the symbolic value corresponding to the file handle.
	SymbolRef FileDesc = Call.getArgSVal(0).getAsSymbol();
	if (!FileDesc)
	return;

	// Check if the stream has already been closed.
	ProgramStateRef State = C.getState();
	const StreamState *SS = State->get<StreamMap>(FileDesc);
	if (SS && SS->isClosed()) {
	reportDoubleClose(FileDesc, Call, C);
	return;
	}

	// Generate the next transition, in which the stream is closed.
	State = State->set<StreamMap>(FileDesc, StreamState::getClosed());
	C.addTransition(State);
	}

	static bool isLeaked(SymbolRef Sym, const StreamState &SS,
	bool IsSymDead, ProgramStateRef State) {
	if (IsSymDead && SS.isOpened()) {
	// If a symbol is NULL, assume that fopen failed on this path.
	// A symbol should only be considered leaked if it is non-null.
	ConstraintManager &CMgr = State->getConstraintManager();
	ConditionTruthVal OpenFailed = CMgr.isNull(State, Sym);
	return !OpenFailed.isConstrainedTrue();
	}
	return false;
	}

	void SimpleStreamChecker::checkDeadSymbols(SymbolReaper &SymReaper,
	CheckerContext &C) const {
	ProgramStateRef State = C.getState();
	SymbolVector LeakedStreams;
	StreamMapTy TrackedStreams = State->get<StreamMap>();
	for (StreamMapTy::iterator I = TrackedStreams.begin(),
	E = TrackedStreams.end(); I != E; ++I) {
	SymbolRef Sym = I->first;
	bool IsSymDead = SymReaper.isDead(Sym);

	// Collect leaked symbols.
	if (isLeaked(Sym, I->second, IsSymDead, State))
	LeakedStreams.push_back(Sym);

	// Remove the dead symbol from the streams map.
	if (IsSymDead)
	State = State->remove<StreamMap>(Sym);
	}

	ExplodedNode *N = C.addTransition(State);
	reportLeaks(LeakedStreams, C, N);
	}

	void SimpleStreamChecker::reportDoubleClose(SymbolRef FileDescSym,
	const CallEvent &Call,
	CheckerContext &C) const {
	// We reached a bug, stop exploring the path here by generating a sink.
	ExplodedNode *ErrNode = C.generateSink();
	// If we've already reached this node on another path, return.
	if (!ErrNode)
	return;

	// Generate the report.
	BugReport R = new BugReport(DoubleCloseBugType,
	"Closing a previously closed file stream", ErrNode);
	R->addRange(Call.getSourceRange());
	R->markInteresting(FileDescSym);
	C.emitReport(R);
	}

	void SimpleStreamChecker::reportLeaks(SymbolVector LeakedStreams,
	CheckerContext &C,
	ExplodedNode *ErrNode) const {
	// Attach bug reports to the leak node.
	// TODO: Identify the leaked file descriptor.
	for (llvm::SmallVector<SymbolRef, 2>::iterator
	I = LeakedStreams.begin(), E = LeakedStreams.end(); I != E; ++I) {
	BugReport R = new BugReport(LeakBugType,
	"Opened file is never closed; potential resource leak", ErrNode);
	R->markInteresting(*I);
	C.emitReport(R);
	}
	}

	// Check various ways a symbol can be invalidated.
	// Stop tracking symbols when a value escapes as a result of checkBind.
	// A value escapes in three possible cases:
	// (1) We are binding to something that is not a memory region.
	// (2) We are binding to a MemRegion that does not have stack storage
	// (3) We are binding to a MemRegion with stack storage that the store
	// does not understand.
	void SimpleStreamChecker::checkBind(SVal loc, SVal val, const Stmt *S,
	CheckerContext &C) const {
	// Are we storing to something that causes the value to "escape"?
	bool escapes = true;
	ProgramStateRef state = C.getState();

	if (loc::MemRegionVal *regionLoc = dyn_cast<loc::MemRegionVal>(&loc)) {
	escapes = !regionLoc->getRegion()->hasStackStorage();

	if (!escapes) {
	// To test (3), generate a new state with the binding added. If it is
	// the same state, then it escapes (since the store cannot represent
	// the binding). Do this only if we know that the store is not supposed
	// to generate the same state.
	SVal StoredVal = state->getSVal(regionLoc->getRegion());
	if (StoredVal != val)
	escapes = (state == (state->bindLoc(*regionLoc, val)));
	}
	}

	// If our store can represent the binding and we aren't storing to something
	// that doesn't have local storage then just return the state and
	// continue as is.
	if (!escapes)
	return;

	// Otherwise, find all symbols referenced by 'val' that we are tracking
	// and stop tracking them.
	state = state->scanReachableSymbols<StopTrackingCallback>(val).getState();
	C.addTransition(state);
	}

	bool SimpleStreamChecker::guaranteedNotToCloseFile(const CallEvent &Call) const{
	// If it's not in a system header, assume it might close a file.
	if (!Call.isInSystemHeader())
	return false;

	// Handle cases where we know a buffer's /address/ can escape.
	if (Call.argumentsMayEscape())
	return false;

	// Note, even though fclose closes the file, we do not list it here
	// since the checker is modeling the call.

	return true;
	}

	// If the symbol we are tracking is invalidated, do not track the symbol as
	// we cannot reason about it anymore.
	ProgramStateRef
	SimpleStreamChecker::checkRegionChanges(ProgramStateRef State,
	const StoreManager::InvalidatedSymbols *invalidated,
	ArrayRef<const MemRegion *> ExplicitRegions,
	ArrayRef<const MemRegion *> Regions,
	const CallEvent *Call) const {

	if (!invalidated \|\| invalidated->empty())
	return State;

	// If it's a call which might close the file, we assume that all regions
	// (explicit and implicit) escaped. Otherwise, whitelist explicit pointers
	// (the parameters to the call); we still can track them.
	llvm::SmallPtrSet<SymbolRef, 8> WhitelistedSymbols;
	if (!Call \|\| guaranteedNotToCloseFile(*Call)) {
	for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
	E = ExplicitRegions.end(); I != E; ++I) {
	if (const SymbolicRegion R = (I)->StripCasts()->getAs<SymbolicRegion>())
	WhitelistedSymbols.insert(R->getSymbol());
	}
	}

	for (StoreManager::InvalidatedSymbols::const_iterator I=invalidated->begin(),
	E = invalidated->end(); I!=E; ++I) {
	SymbolRef sym = *I;
	if (WhitelistedSymbols.count(sym))
	continue;
	// The symbol escaped. Optimistically, assume that the corresponding file
	// handle will be closed somewhere else.
	State = State->remove<StreamMap>(sym);
	}
	return State;
	}

	void SimpleStreamChecker::initIdentifierInfo(ASTContext &Ctx) const {
	if (IIfopen)
	return;
	IIfopen = &Ctx.Idents.get("fopen");
	IIfclose = &Ctx.Idents.get("fclose");
	}

	void ento::registerSimpleStreamChecker(CheckerManager &mgr) {
	mgr.registerChecker<SimpleStreamChecker>();
	}