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//===-- 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/CheckerContext.h"
using namespace clang;
using namespace ento;
namespace {
typedef llvm::SmallVector<SymbolRef, 2> SymbolVector;
struct StreamState {
enum Kind { Opened, Closed } K;
StreamState(Kind InK) : K(InK) { }
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::PostStmt<CallExpr>,
check::PreStmt<CallExpr>,
check::DeadSymbols,
eval::Assume > {
mutable IdentifierInfo *IIfopen, *IIfclose;
mutable OwningPtr<BugType> DoubleCloseBugType;
mutable OwningPtr<BugType> LeakBugType;
void initIdentifierInfo(ASTContext &Ctx) const;
void reportDoubleClose(SymbolRef FileDescSym,
const CallExpr *Call,
CheckerContext &C) const;
ExplodedNode *reportLeaks(SymbolVector LeakedStreams,
CheckerContext &C) const;
public:
SimpleStreamChecker() : IIfopen(0), IIfclose(0) {}
/// Process fopen.
void checkPostStmt(const CallExpr *Call, CheckerContext &C) const;
/// Process fclose.
void checkPreStmt(const CallExpr *Call, CheckerContext &C) const;
void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
ProgramStateRef evalAssume(ProgramStateRef state, SVal Cond,
bool Assumption) const;
};
} // 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)
void SimpleStreamChecker::checkPostStmt(const CallExpr *Call,
CheckerContext &C) const {
initIdentifierInfo(C.getASTContext());
if (C.getCalleeIdentifier(Call) != IIfopen)
return;
// Get the symbolic value corresponding to the file handle.
SymbolRef FileDesc = C.getSVal(Call).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::checkPreStmt(const CallExpr *Call,
CheckerContext &C) const {
initIdentifierInfo(C.getASTContext());
if (C.getCalleeIdentifier(Call) != IIfclose || Call->getNumArgs() != 1)
return;
// Get the symbolic value corresponding to the file handle.
SymbolRef FileDesc = C.getSVal(Call->getArg(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);
// Generate the next transition, in which the stream is closed.
State = State->set<StreamMap>(FileDesc, StreamState::getClosed());
C.addTransition(State);
}
void SimpleStreamChecker::checkDeadSymbols(SymbolReaper &SymReaper,
CheckerContext &C) const {
ProgramStateRef State = C.getState();
StreamMapTy TrackedStreams = State->get<StreamMap>();
SymbolVector LeakedStreams;
for (StreamMapTy::iterator I = TrackedStreams.begin(),
E = TrackedStreams.end(); I != E; ++I) {
SymbolRef Sym = I->first;
if (SymReaper.isDead(Sym)) {
const StreamState &SS = I->second;
if (SS.isOpened())
LeakedStreams.push_back(Sym);
// Remove the dead symbol from the streams map.
State = State->remove<StreamMap>(Sym);
}
}
ExplodedNode *N = reportLeaks(LeakedStreams, C);
C.addTransition(State, N);
}
// If a symbolic region is assumed to NULL (or another constant), stop tracking
// it - assuming that allocation failed on this path.
ProgramStateRef SimpleStreamChecker::evalAssume(ProgramStateRef State,
SVal Cond,
bool Assumption) const {
StreamMapTy TrackedStreams = State->get<StreamMap>();
SymbolVector LeakedStreams;
for (StreamMapTy::iterator I = TrackedStreams.begin(),
E = TrackedStreams.end(); I != E; ++I) {
SymbolRef Sym = I->first;
if (State->getConstraintManager().isNull(State, Sym).isTrue())
State = State->remove<StreamMap>(Sym);
}
return State;
}
void SimpleStreamChecker::reportDoubleClose(SymbolRef FileDescSym,
const CallExpr *CallExpr,
CheckerContext &C) const {
// We reached a bug, stop exploring the path here by generating a sink.
ExplodedNode *ErrNode = C.generateSink();
// If this error node already exists, return.
if (!ErrNode)
return;
// Initialize the bug type.
if (!DoubleCloseBugType)
DoubleCloseBugType.reset(new BugType("Double fclose",
"Unix Stream API Error"));
// Generate the report.
BugReport *R = new BugReport(*DoubleCloseBugType,
"Closing a previously closed file stream", ErrNode);
R->addRange(CallExpr->getSourceRange());
R->markInteresting(FileDescSym);
C.EmitReport(R);
}
ExplodedNode *SimpleStreamChecker::reportLeaks(SymbolVector LeakedStreams,
CheckerContext &C) const {
ExplodedNode *Pred = C.getPredecessor();
if (LeakedStreams.empty())
return Pred;
// Generate an intermediate node representing the leak point.
static SimpleProgramPointTag Tag("StreamChecker : Leak");
ExplodedNode *ErrNode = C.addTransition(Pred->getState(), Pred, &Tag);
if (!ErrNode)
return Pred;
// Initialize the bug type.
if (!LeakBugType) {
LeakBugType.reset(new BuiltinBug("Resource Leak",
"Unix Stream API Error"));
// Sinks are higher importance bugs as well as calls to assert() or exit(0).
LeakBugType->setSuppressOnSink(true);
}
// 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);
}
return ErrNode;
}
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>();
}
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