// BugReporterVisitors.cpp - Helpers for reporting bugs -----------*- C++ -*--//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines a set of BugReporter "visitors" which can be used to
// enhance the diagnostics reported for a bug.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Core/BugReporter/BugReporterVisitor.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprObjC.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
#include "clang/StaticAnalyzer/Core/BugReporter/PathDiagnostic.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/raw_ostream.h"
using namespace clang;
using namespace ento;
using llvm::FoldingSetNodeID;
//===----------------------------------------------------------------------===//
// Utility functions.
//===----------------------------------------------------------------------===//
bool bugreporter::isDeclRefExprToReference(const Expr *E) {
if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
return DRE->getDecl()->getType()->isReferenceType();
}
return false;
}
const Expr *bugreporter::getDerefExpr(const Stmt *S) {
// Pattern match for a few useful cases:
// a[0], p->f, *p
const Expr *E = dyn_cast<Expr>(S);
if (!E)
return nullptr;
E = E->IgnoreParenCasts();
while (true) {
if (const BinaryOperator *B = dyn_cast<BinaryOperator>(E)) {
assert(B->isAssignmentOp());
E = B->getLHS()->IgnoreParenCasts();
continue;
}
else if (const UnaryOperator *U = dyn_cast<UnaryOperator>(E)) {
if (U->getOpcode() == UO_Deref)
return U->getSubExpr()->IgnoreParenCasts();
}
else if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
if (ME->isArrow() || isDeclRefExprToReference(ME->getBase())) {
return ME->getBase()->IgnoreParenCasts();
} else {
// If we have a member expr with a dot, the base must have been
// dereferenced.
return getDerefExpr(ME->getBase());
}
}
else if (const ObjCIvarRefExpr *IvarRef = dyn_cast<ObjCIvarRefExpr>(E)) {
return IvarRef->getBase()->IgnoreParenCasts();
}
else if (const ArraySubscriptExpr *AE = dyn_cast<ArraySubscriptExpr>(E)) {
return AE->getBase();
}
else if (isDeclRefExprToReference(E)) {
return E;
}
break;
}
return nullptr;
}
const Stmt *bugreporter::GetDenomExpr(const ExplodedNode *N) {
const Stmt *S = N->getLocationAs<PreStmt>()->getStmt();
if (const BinaryOperator *BE = dyn_cast<BinaryOperator>(S))
return BE->getRHS();
return nullptr;
}
const Stmt *bugreporter::GetRetValExpr(const ExplodedNode *N) {
const Stmt *S = N->getLocationAs<PostStmt>()->getStmt();
if (const ReturnStmt *RS = dyn_cast<ReturnStmt>(S))
return RS->getRetValue();
return nullptr;
}
//===----------------------------------------------------------------------===//
// Definitions for bug reporter visitors.
//===----------------------------------------------------------------------===//
std::unique_ptr<PathDiagnosticPiece>
BugReporterVisitor::getEndPath(BugReporterContext &BRC,
const ExplodedNode *EndPathNode, BugReport &BR) {
return nullptr;
}
std::unique_ptr<PathDiagnosticPiece> BugReporterVisitor::getDefaultEndPath(
BugReporterContext &BRC, const ExplodedNode *EndPathNode, BugReport &BR) {
PathDiagnosticLocation L =
PathDiagnosticLocation::createEndOfPath(EndPathNode,BRC.getSourceManager());
const auto &Ranges = BR.getRanges();
// Only add the statement itself as a range if we didn't specify any
// special ranges for this report.
auto P = llvm::make_unique<PathDiagnosticEventPiece>(
L, BR.getDescription(), Ranges.begin() == Ranges.end());
for (SourceRange Range : Ranges)
P->addRange(Range);
return std::move(P);
}
namespace {
/// Emits an extra note at the return statement of an interesting stack frame.
///
/// The returned value is marked as an interesting value, and if it's null,
/// adds a visitor to track where it became null.
///
/// This visitor is intended to be used when another visitor discovers that an
/// interesting value comes from an inlined function call.
class ReturnVisitor : public BugReporterVisitorImpl<ReturnVisitor> {
const StackFrameContext *StackFrame;
enum {
Initial,
MaybeUnsuppress,
Satisfied
} Mode;
bool EnableNullFPSuppression;
public:
ReturnVisitor(const StackFrameContext *Frame, bool Suppressed)
: StackFrame(Frame), Mode(Initial), EnableNullFPSuppression(Suppressed) {}
static void *getTag() {
static int Tag = 0;
return static_cast<void *>(&Tag);
}
void Profile(llvm::FoldingSetNodeID &ID) const override {
ID.AddPointer(ReturnVisitor::getTag());
ID.AddPointer(StackFrame);
ID.AddBoolean(EnableNullFPSuppression);
}
/// Adds a ReturnVisitor if the given statement represents a call that was
/// inlined.
///
/// This will search back through the ExplodedGraph, starting from the given
/// node, looking for when the given statement was processed. If it turns out
/// the statement is a call that was inlined, we add the visitor to the
/// bug report, so it can print a note later.
static void addVisitorIfNecessary(const ExplodedNode *Node, const Stmt *S,
BugReport &BR,
bool InEnableNullFPSuppression) {
if (!CallEvent::isCallStmt(S))
return;
// First, find when we processed the statement.
do {
if (Optional<CallExitEnd> CEE = Node->getLocationAs<CallExitEnd>())
if (CEE->getCalleeContext()->getCallSite() == S)
break;
if (Optional<StmtPoint> SP = Node->getLocationAs<StmtPoint>())
if (SP->getStmt() == S)
break;
Node = Node->getFirstPred();
} while (Node);
// Next, step over any post-statement checks.
while (Node && Node->getLocation().getAs<PostStmt>())
Node = Node->getFirstPred();
if (!Node)
return;
// Finally, see if we inlined the call.
Optional<CallExitEnd> CEE = Node->getLocationAs<CallExitEnd>();
if (!CEE)
return;
const StackFrameContext *CalleeContext = CEE->getCalleeContext();
if (CalleeContext->getCallSite() != S)
return;
// Check the return value.
ProgramStateRef State = Node->getState();
SVal RetVal = State->getSVal(S, Node->getLocationContext());
// Handle cases where a reference is returned and then immediately used.
if (cast<Expr>(S)->isGLValue())
if (Optional<Loc> LValue = RetVal.getAs<Loc>())
RetVal = State->getSVal(*LValue);
// See if the return value is NULL. If so, suppress the report.
SubEngine *Eng = State->getStateManager().getOwningEngine();
assert(Eng && "Cannot file a bug report without an owning engine");
AnalyzerOptions &Options = Eng->getAnalysisManager().options;
bool EnableNullFPSuppression = false;
if (InEnableNullFPSuppression && Options.shouldSuppressNullReturnPaths())
if (Optional<Loc> RetLoc = RetVal.getAs<Loc>())
EnableNullFPSuppression = State->isNull(*RetLoc).isConstrainedTrue();
BR.markInteresting(CalleeContext);
BR.addVisitor(llvm::make_unique<ReturnVisitor>(CalleeContext,
EnableNullFPSuppression));
}
/// Returns true if any counter-suppression heuristics are enabled for
/// ReturnVisitor.
static bool hasCounterSuppression(AnalyzerOptions &Options) {
return Options.shouldAvoidSuppressingNullArgumentPaths();
}
PathDiagnosticPiece *visitNodeInitial(const ExplodedNode *N,
const ExplodedNode *PrevN,
BugReporterContext &BRC,
BugReport &BR) {
// Only print a message at the interesting return statement.
if (N->getLocationContext() != StackFrame)
return nullptr;
Optional<StmtPoint> SP = N->getLocationAs<StmtPoint>();
if (!SP)
return nullptr;
const ReturnStmt *Ret = dyn_cast<ReturnStmt>(SP->getStmt());
if (!Ret)
return nullptr;
// Okay, we're at the right return statement, but do we have the return
// value available?
ProgramStateRef State = N->getState();
SVal V = State->getSVal(Ret, StackFrame);
if (V.isUnknownOrUndef())
return nullptr;
// Don't print any more notes after this one.
Mode = Satisfied;
const Expr *RetE = Ret->getRetValue();
assert(RetE && "Tracking a return value for a void function");
// Handle cases where a reference is returned and then immediately used.
Optional<Loc> LValue;
if (RetE->isGLValue()) {
if ((LValue = V.getAs<Loc>())) {
SVal RValue = State->getRawSVal(*LValue, RetE->getType());
if (RValue.getAs<DefinedSVal>())
V = RValue;
}
}
// Ignore aggregate rvalues.
if (V.getAs<nonloc::LazyCompoundVal>() ||
V.getAs<nonloc::CompoundVal>())
return nullptr;
RetE = RetE->IgnoreParenCasts();
// If we can't prove the return value is 0, just mark it interesting, and
// make sure to track it into any further inner functions.
if (!State->isNull(V).isConstrainedTrue()) {
BR.markInteresting(V);
ReturnVisitor::addVisitorIfNecessary(N, RetE, BR,
EnableNullFPSuppression);
return nullptr;
}
// If we're returning 0, we should track where that 0 came from.
bugreporter::trackNullOrUndefValue(N, RetE, BR, /*IsArg*/ false,
EnableNullFPSuppression);
// Build an appropriate message based on the return value.
SmallString<64> Msg;
llvm::raw_svector_ostream Out(Msg);
if (V.getAs<Loc>()) {
// If we have counter-suppression enabled, make sure we keep visiting
// future nodes. We want to emit a path note as well, in case
// the report is resurrected as valid later on.
ExprEngine &Eng = BRC.getBugReporter().getEngine();
AnalyzerOptions &Options = Eng.getAnalysisManager().options;
if (EnableNullFPSuppression && hasCounterSuppression(Options))
Mode = MaybeUnsuppress;
if (RetE->getType()->isObjCObjectPointerType())
Out << "Returning nil";
else
Out << "Returning null pointer";
} else {
Out << "Returning zero";
}
if (LValue) {
if (const MemRegion *MR = LValue->getAsRegion()) {
if (MR->canPrintPretty()) {
Out << " (reference to ";
MR->printPretty(Out);
Out << ")";
}
}
} else {
// FIXME: We should have a more generalized location printing mechanism.
if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(RetE))
if (const DeclaratorDecl *DD = dyn_cast<DeclaratorDecl>(DR->getDecl()))
Out << " (loaded from '" << *DD << "')";
}
PathDiagnosticLocation L(Ret, BRC.getSourceManager(), StackFrame);
return new PathDiagnosticEventPiece(L, Out.str());
}
PathDiagnosticPiece *visitNodeMaybeUnsuppress(const ExplodedNode *N,
const ExplodedNode *PrevN,
BugReporterContext &BRC,
BugReport &BR) {
#ifndef NDEBUG
ExprEngine &Eng = BRC.getBugReporter().getEngine();
AnalyzerOptions &Options = Eng.getAnalysisManager().options;
assert(hasCounterSuppression(Options));
#endif
// Are we at the entry node for this call?
Optional<CallEnter> CE = N->getLocationAs<CallEnter>();
if (!CE)
return nullptr;
if (CE->getCalleeContext() != StackFrame)
return nullptr;
Mode = Satisfied;
// Don't automatically suppress a report if one of the arguments is
// known to be a null pointer. Instead, start tracking /that/ null
// value back to its origin.
ProgramStateManager &StateMgr = BRC.getStateManager();
CallEventManager &CallMgr = StateMgr.getCallEventManager();
ProgramStateRef State = N->getState();
CallEventRef<> Call = CallMgr.getCaller(StackFrame, State);
for (unsigned I = 0, E = Call->getNumArgs(); I != E; ++I) {
Optional<Loc> ArgV = Call->getArgSVal(I).getAs<Loc>();
if (!ArgV)
continue;
const Expr *ArgE = Call->getArgExpr(I);
if (!ArgE)
continue;
// Is it possible for this argument to be non-null?
if (!State->isNull(*ArgV).isConstrainedTrue())
continue;
if (bugreporter::trackNullOrUndefValue(N, ArgE, BR, /*IsArg=*/true,
EnableNullFPSuppression))
BR.removeInvalidation(ReturnVisitor::getTag(), StackFrame);
// If we /can't/ track the null pointer, we should err on the side of
// false negatives, and continue towards marking this report invalid.
// (We will still look at the other arguments, though.)
}
return nullptr;
}
PathDiagnosticPiece *VisitNode(const ExplodedNode *N,
const ExplodedNode *PrevN,
BugReporterContext &BRC,
BugReport &BR) override {
switch (Mode) {
case Initial:
return visitNodeInitial(N, PrevN, BRC, BR);
case MaybeUnsuppress:
return visitNodeMaybeUnsuppress(N, PrevN, BRC, BR);
case Satisfied:
return nullptr;
}
llvm_unreachable("Invalid visit mode!");
}
std::unique_ptr<PathDiagnosticPiece> getEndPath(BugReporterContext &BRC,
const ExplodedNode *N,
BugReport &BR) override {
if (EnableNullFPSuppression)
BR.markInvalid(ReturnVisitor::getTag(), StackFrame);
return nullptr;
}
};
} // end anonymous namespace
void FindLastStoreBRVisitor ::Profile(llvm::FoldingSetNodeID &ID) const {
static int tag = 0;
ID.AddPointer(&tag);
ID.AddPointer(R);
ID.Add(V);
ID.AddBoolean(EnableNullFPSuppression);
}
/// Returns true if \p N represents the DeclStmt declaring and initializing
/// \p VR.
static bool isInitializationOfVar(const ExplodedNode *N, const VarRegion *VR) {
Optional<PostStmt> P = N->getLocationAs<PostStmt>();
if (!P)
return false;
const DeclStmt *DS = P->getStmtAs<DeclStmt>();
if (!DS)
return false;
if (DS->getSingleDecl() != VR->getDecl())
return false;
const MemSpaceRegion *VarSpace = VR->getMemorySpace();
const StackSpaceRegion *FrameSpace = dyn_cast<StackSpaceRegion>(VarSpace);
if (!FrameSpace) {
// If we ever directly evaluate global DeclStmts, this assertion will be
// invalid, but this still seems preferable to silently accepting an
// initialization that may be for a path-sensitive variable.
assert(VR->getDecl()->isStaticLocal() && "non-static stackless VarRegion");
return true;
}
assert(VR->getDecl()->hasLocalStorage());
const LocationContext *LCtx = N->getLocationContext();
return FrameSpace->getStackFrame() == LCtx->getCurrentStackFrame();
}
PathDiagnosticPiece *FindLastStoreBRVisitor::VisitNode(const ExplodedNode *Succ,
const ExplodedNode *Pred,
BugReporterContext &BRC,
BugReport &BR) {
if (Satisfied)
return nullptr;
const ExplodedNode *StoreSite = nullptr;
const Expr *InitE = nullptr;
bool IsParam = false;
// First see if we reached the declaration of the region.
if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
if (isInitializationOfVar(Pred, VR)) {
StoreSite = Pred;
InitE = VR->getDecl()->getInit();
}
}
// If this is a post initializer expression, initializing the region, we
// should track the initializer expression.
if (Optional<PostInitializer> PIP = Pred->getLocationAs<PostInitializer>()) {
const MemRegion *FieldReg = (const MemRegion *)PIP->getLocationValue();
if (FieldReg && FieldReg == R) {
StoreSite = Pred;
InitE = PIP->getInitializer()->getInit();
}
}
// Otherwise, see if this is the store site:
// (1) Succ has this binding and Pred does not, i.e. this is
// where the binding first occurred.
// (2) Succ has this binding and is a PostStore node for this region, i.e.
// the same binding was re-assigned here.
if (!StoreSite) {
if (Succ->getState()->getSVal(R) != V)
return nullptr;
if (Pred->getState()->getSVal(R) == V) {
Optional<PostStore> PS = Succ->getLocationAs<PostStore>();
if (!PS || PS->getLocationValue() != R)
return nullptr;
}
StoreSite = Succ;
// If this is an assignment expression, we can track the value
// being assigned.
if (Optional<PostStmt> P = Succ->getLocationAs<PostStmt>())
if (const BinaryOperator *BO = P->getStmtAs<BinaryOperator>())
if (BO->isAssignmentOp())
InitE = BO->getRHS();
// If this is a call entry, the variable should be a parameter.
// FIXME: Handle CXXThisRegion as well. (This is not a priority because
// 'this' should never be NULL, but this visitor isn't just for NULL and
// UndefinedVal.)
if (Optional<CallEnter> CE = Succ->getLocationAs<CallEnter>()) {
if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
const ParmVarDecl *Param = cast<ParmVarDecl>(VR->getDecl());
ProgramStateManager &StateMgr = BRC.getStateManager();
CallEventManager &CallMgr = StateMgr.getCallEventManager();
CallEventRef<> Call = CallMgr.getCaller(CE->getCalleeContext(),
Succ->getState());
InitE = Call->getArgExpr(Param->getFunctionScopeIndex());
IsParam = true;
}
}
// If this is a CXXTempObjectRegion, the Expr responsible for its creation
// is wrapped inside of it.
if (const CXXTempObjectRegion *TmpR = dyn_cast<CXXTempObjectRegion>(R))
InitE = TmpR->getExpr();
}
if (!StoreSite)
return nullptr;
Satisfied = true;
// If we have an expression that provided the value, try to track where it
// came from.
if (InitE) {
if (V.isUndef() ||
V.getAs<loc::ConcreteInt>() || V.getAs<nonloc::ConcreteInt>()) {
if (!IsParam)
InitE = InitE->IgnoreParenCasts();
bugreporter::trackNullOrUndefValue(StoreSite, InitE, BR, IsParam,
EnableNullFPSuppression);
} else {
ReturnVisitor::addVisitorIfNecessary(StoreSite, InitE->IgnoreParenCasts(),
BR, EnableNullFPSuppression);
}
}
// Okay, we've found the binding. Emit an appropriate message.
SmallString<256> sbuf;
llvm::raw_svector_ostream os(sbuf);
if (Optional<PostStmt> PS = StoreSite->getLocationAs<PostStmt>()) {
const Stmt *S = PS->getStmt();
const char *action = nullptr;
const DeclStmt *DS = dyn_cast<DeclStmt>(S);
const VarRegion *VR = dyn_cast<VarRegion>(R);
if (DS) {
action = R->canPrintPretty() ? "initialized to " :
"Initializing to ";
} else if (isa<BlockExpr>(S)) {
action = R->canPrintPretty() ? "captured by block as " :
"Captured by block as ";
if (VR) {
// See if we can get the BlockVarRegion.
ProgramStateRef State = StoreSite->getState();
SVal V = State->getSVal(S, PS->getLocationContext());
if (const BlockDataRegion *BDR =
dyn_cast_or_null<BlockDataRegion>(V.getAsRegion())) {
if (const VarRegion *OriginalR = BDR->getOriginalRegion(VR)) {
if (Optional<KnownSVal> KV =
State->getSVal(OriginalR).getAs<KnownSVal>())
BR.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
*KV, OriginalR, EnableNullFPSuppression));
}
}
}
}
if (action) {
if (R->canPrintPretty()) {
R->printPretty(os);
os << " ";
}
if (V.getAs<loc::ConcreteInt>()) {
bool b = false;
if (R->isBoundable()) {
if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) {
if (TR->getValueType()->isObjCObjectPointerType()) {
os << action << "nil";
b = true;
}
}
}
if (!b)
os << action << "a null pointer value";
} else if (Optional<nonloc::ConcreteInt> CVal =
V.getAs<nonloc::ConcreteInt>()) {
os << action << CVal->getValue();
}
else if (DS) {
if (V.isUndef()) {
if (isa<VarRegion>(R)) {
const VarDecl *VD = cast<VarDecl>(DS->getSingleDecl());
if (VD->getInit()) {
os << (R->canPrintPretty() ? "initialized" : "Initializing")
<< " to a garbage value";
} else {
os << (R->canPrintPretty() ? "declared" : "Declaring")
<< " without an initial value";
}
}
}
else {
os << (R->canPrintPretty() ? "initialized" : "Initialized")
<< " here";
}
}
}
} else if (StoreSite->getLocation().getAs<CallEnter>()) {
if (const VarRegion *VR = dyn_cast<VarRegion>(R)) {
const ParmVarDecl *Param = cast<ParmVarDecl>(VR->getDecl());
os << "Passing ";
if (V.getAs<loc::ConcreteInt>()) {
if (Param->getType()->isObjCObjectPointerType())
os << "nil object reference";
else
os << "null pointer value";
} else if (V.isUndef()) {
os << "uninitialized value";
} else if (Optional<nonloc::ConcreteInt> CI =
V.getAs<nonloc::ConcreteInt>()) {
os << "the value " << CI->getValue();
} else {
os << "value";
}
// Printed parameter indexes are 1-based, not 0-based.
unsigned Idx = Param->getFunctionScopeIndex() + 1;
os << " via " << Idx << llvm::getOrdinalSuffix(Idx) << " parameter";
if (R->canPrintPretty()) {
os << " ";
R->printPretty(os);
}
}
}
if (os.str().empty()) {
if (V.getAs<loc::ConcreteInt>()) {
bool b = false;
if (R->isBoundable()) {
if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) {
if (TR->getValueType()->isObjCObjectPointerType()) {
os << "nil object reference stored";
b = true;
}
}
}
if (!b) {
if (R->canPrintPretty())
os << "Null pointer value stored";
else
os << "Storing null pointer value";
}
} else if (V.isUndef()) {
if (R->canPrintPretty())
os << "Uninitialized value stored";
else
os << "Storing uninitialized value";
} else if (Optional<nonloc::ConcreteInt> CV =
V.getAs<nonloc::ConcreteInt>()) {
if (R->canPrintPretty())
os << "The value " << CV->getValue() << " is assigned";
else
os << "Assigning " << CV->getValue();
} else {
if (R->canPrintPretty())
os << "Value assigned";
else
os << "Assigning value";
}
if (R->canPrintPretty()) {
os << " to ";
R->printPretty(os);
}
}
// Construct a new PathDiagnosticPiece.
ProgramPoint P = StoreSite->getLocation();
PathDiagnosticLocation L;
if (P.getAs<CallEnter>() && InitE)
L = PathDiagnosticLocation(InitE, BRC.getSourceManager(),
P.getLocationContext());
if (!L.isValid() || !L.asLocation().isValid())
L = PathDiagnosticLocation::create(P, BRC.getSourceManager());
if (!L.isValid() || !L.asLocation().isValid())
return nullptr;
return new PathDiagnosticEventPiece(L, os.str());
}
void TrackConstraintBRVisitor::Profile(llvm::FoldingSetNodeID &ID) const {
static int tag = 0;
ID.AddPointer(&tag);
ID.AddBoolean(Assumption);
ID.Add(Constraint);
}
/// Return the tag associated with this visitor. This tag will be used
/// to make all PathDiagnosticPieces created by this visitor.
const char *TrackConstraintBRVisitor::getTag() {
return "TrackConstraintBRVisitor";
}
bool TrackConstraintBRVisitor::isUnderconstrained(const ExplodedNode *N) const {
if (IsZeroCheck)
return N->getState()->isNull(Constraint).isUnderconstrained();
return (bool)N->getState()->assume(Constraint, !Assumption);
}
PathDiagnosticPiece *
TrackConstraintBRVisitor::VisitNode(const ExplodedNode *N,
const ExplodedNode *PrevN,
BugReporterContext &BRC,
BugReport &BR) {
if (IsSatisfied)
return nullptr;
// Start tracking after we see the first state in which the value is
// constrained.
if (!IsTrackingTurnedOn)
if (!isUnderconstrained(N))
IsTrackingTurnedOn = true;
if (!IsTrackingTurnedOn)
return nullptr;
// Check if in the previous state it was feasible for this constraint
// to *not* be true.
if (isUnderconstrained(PrevN)) {
IsSatisfied = true;
// As a sanity check, make sure that the negation of the constraint
// was infeasible in the current state. If it is feasible, we somehow
// missed the transition point.
assert(!isUnderconstrained(N));
// We found the transition point for the constraint. We now need to
// pretty-print the constraint. (work-in-progress)
SmallString<64> sbuf;
llvm::raw_svector_ostream os(sbuf);
if (Constraint.getAs<Loc>()) {
os << "Assuming pointer value is ";
os << (Assumption ? "non-null" : "null");
}
if (os.str().empty())
return nullptr;
// Construct a new PathDiagnosticPiece.
ProgramPoint P = N->getLocation();
PathDiagnosticLocation L =
PathDiagnosticLocation::create(P, BRC.getSourceManager());
if (!L.isValid())
return nullptr;
PathDiagnosticEventPiece *X = new PathDiagnosticEventPiece(L, os.str());
X->setTag(getTag());
return X;
}
return nullptr;
}
SuppressInlineDefensiveChecksVisitor::
SuppressInlineDefensiveChecksVisitor(DefinedSVal Value, const ExplodedNode *N)
: V(Value), IsSatisfied(false), IsTrackingTurnedOn(false) {
// Check if the visitor is disabled.
SubEngine *Eng = N->getState()->getStateManager().getOwningEngine();
assert(Eng && "Cannot file a bug report without an owning engine");
AnalyzerOptions &Options = Eng->getAnalysisManager().options;
if (!Options.shouldSuppressInlinedDefensiveChecks())
IsSatisfied = true;
assert(N->getState()->isNull(V).isConstrainedTrue() &&
"The visitor only tracks the cases where V is constrained to 0");
}
void SuppressInlineDefensiveChecksVisitor::Profile(FoldingSetNodeID &ID) const {
static int id = 0;
ID.AddPointer(&id);
ID.Add(V);
}
const char *SuppressInlineDefensiveChecksVisitor::getTag() {
return "IDCVisitor";
}
PathDiagnosticPiece *
SuppressInlineDefensiveChecksVisitor::VisitNode(const ExplodedNode *Succ,
const ExplodedNode *Pred,
BugReporterContext &BRC,
BugReport &BR) {
if (IsSatisfied)
return nullptr;
// Start tracking after we see the first state in which the value is null.
if (!IsTrackingTurnedOn)
if (Succ->getState()->isNull(V).isConstrainedTrue())
IsTrackingTurnedOn = true;
if (!IsTrackingTurnedOn)
return nullptr;
// Check if in the previous state it was feasible for this value
// to *not* be null.
if (!Pred->getState()->isNull(V).isConstrainedTrue()) {
IsSatisfied = true;
assert(Succ->getState()->isNull(V).isConstrainedTrue());
// Check if this is inlined defensive checks.
const LocationContext *CurLC =Succ->getLocationContext();
const LocationContext *ReportLC = BR.getErrorNode()->getLocationContext();
if (CurLC != ReportLC && !CurLC->isParentOf(ReportLC))
BR.markInvalid("Suppress IDC", CurLC);
}
return nullptr;
}
static const MemRegion *getLocationRegionIfReference(const Expr *E,
const ExplodedNode *N) {
if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(E)) {
if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
if (!VD->getType()->isReferenceType())
return nullptr;
ProgramStateManager &StateMgr = N->getState()->getStateManager();
MemRegionManager &MRMgr = StateMgr.getRegionManager();
return MRMgr.getVarRegion(VD, N->getLocationContext());
}
}
// FIXME: This does not handle other kinds of null references,
// for example, references from FieldRegions:
// struct Wrapper { int &ref; };
// Wrapper w = { *(int *)0 };
// w.ref = 1;
return nullptr;
}
static const Expr *peelOffOuterExpr(const Expr *Ex,
const ExplodedNode *N) {
Ex = Ex->IgnoreParenCasts();
if (const ExprWithCleanups *EWC = dyn_cast<ExprWithCleanups>(Ex))
return peelOffOuterExpr(EWC->getSubExpr(), N);
if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(Ex))
return peelOffOuterExpr(OVE->getSourceExpr(), N);
// Peel off the ternary operator.
if (const ConditionalOperator *CO = dyn_cast<ConditionalOperator>(Ex)) {
// Find a node where the branching occurred and find out which branch
// we took (true/false) by looking at the ExplodedGraph.
const ExplodedNode *NI = N;
do {
ProgramPoint ProgPoint = NI->getLocation();
if (Optional<BlockEdge> BE = ProgPoint.getAs<BlockEdge>()) {
const CFGBlock *srcBlk = BE->getSrc();
if (const Stmt *term = srcBlk->getTerminator()) {
if (term == CO) {
bool TookTrueBranch = (*(srcBlk->succ_begin()) == BE->getDst());
if (TookTrueBranch)
return peelOffOuterExpr(CO->getTrueExpr(), N);
else
return peelOffOuterExpr(CO->getFalseExpr(), N);
}
}
}
NI = NI->getFirstPred();
} while (NI);
}
return Ex;
}
bool bugreporter::trackNullOrUndefValue(const ExplodedNode *N,
const Stmt *S,
BugReport &report, bool IsArg,
bool EnableNullFPSuppression) {
if (!S || !N)
return false;
if (const Expr *Ex = dyn_cast<Expr>(S)) {
Ex = Ex->IgnoreParenCasts();
const Expr *PeeledEx = peelOffOuterExpr(Ex, N);
if (Ex != PeeledEx)
S = PeeledEx;
}
const Expr *Inner = nullptr;
if (const Expr *Ex = dyn_cast<Expr>(S)) {
Ex = Ex->IgnoreParenCasts();
if (ExplodedGraph::isInterestingLValueExpr(Ex) || CallEvent::isCallStmt(Ex))
Inner = Ex;
}
if (IsArg && !Inner) {
assert(N->getLocation().getAs<CallEnter>() && "Tracking arg but not at call");
} else {
// Walk through nodes until we get one that matches the statement exactly.
// Alternately, if we hit a known lvalue for the statement, we know we've
// gone too far (though we can likely track the lvalue better anyway).
do {
const ProgramPoint &pp = N->getLocation();
if (Optional<StmtPoint> ps = pp.getAs<StmtPoint>()) {
if (ps->getStmt() == S || ps->getStmt() == Inner)
break;
} else if (Optional<CallExitEnd> CEE = pp.getAs<CallExitEnd>()) {
if (CEE->getCalleeContext()->getCallSite() == S ||
CEE->getCalleeContext()->getCallSite() == Inner)
break;
}
N = N->getFirstPred();
} while (N);
if (!N)
return false;
}
ProgramStateRef state = N->getState();
// The message send could be nil due to the receiver being nil.
// At this point in the path, the receiver should be live since we are at the
// message send expr. If it is nil, start tracking it.
if (const Expr *Receiver = NilReceiverBRVisitor::getNilReceiver(S, N))
trackNullOrUndefValue(N, Receiver, report, false, EnableNullFPSuppression);
// See if the expression we're interested refers to a variable.
// If so, we can track both its contents and constraints on its value.
if (Inner && ExplodedGraph::isInterestingLValueExpr(Inner)) {
const MemRegion *R = nullptr;
// Find the ExplodedNode where the lvalue (the value of 'Ex')
// was computed. We need this for getting the location value.
const ExplodedNode *LVNode = N;
while (LVNode) {
if (Optional<PostStmt> P = LVNode->getLocation().getAs<PostStmt>()) {
if (P->getStmt() == Inner)
break;
}
LVNode = LVNode->getFirstPred();
}
assert(LVNode && "Unable to find the lvalue node.");
ProgramStateRef LVState = LVNode->getState();
SVal LVal = LVState->getSVal(Inner, LVNode->getLocationContext());
if (LVState->isNull(LVal).isConstrainedTrue()) {
// In case of C++ references, we want to differentiate between a null
// reference and reference to null pointer.
// If the LVal is null, check if we are dealing with null reference.
// For those, we want to track the location of the reference.
if (const MemRegion *RR = getLocationRegionIfReference(Inner, N))
R = RR;
} else {
R = LVState->getSVal(Inner, LVNode->getLocationContext()).getAsRegion();
// If this is a C++ reference to a null pointer, we are tracking the
// pointer. In additon, we should find the store at which the reference
// got initialized.
if (const MemRegion *RR = getLocationRegionIfReference(Inner, N)) {
if (Optional<KnownSVal> KV = LVal.getAs<KnownSVal>())
report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
*KV, RR, EnableNullFPSuppression));
}
}
if (R) {
// Mark both the variable region and its contents as interesting.
SVal V = LVState->getRawSVal(loc::MemRegionVal(R));
report.markInteresting(R);
report.markInteresting(V);
report.addVisitor(llvm::make_unique<UndefOrNullArgVisitor>(R));
// If the contents are symbolic, find out when they became null.
if (V.getAsLocSymbol(/*IncludeBaseRegions*/ true))
report.addVisitor(llvm::make_unique<TrackConstraintBRVisitor>(
V.castAs<DefinedSVal>(), false));
// Add visitor, which will suppress inline defensive checks.
if (Optional<DefinedSVal> DV = V.getAs<DefinedSVal>()) {
if (!DV->isZeroConstant() && LVState->isNull(*DV).isConstrainedTrue() &&
EnableNullFPSuppression) {
report.addVisitor(
llvm::make_unique<SuppressInlineDefensiveChecksVisitor>(*DV,
LVNode));
}
}
if (Optional<KnownSVal> KV = V.getAs<KnownSVal>())
report.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
*KV, R, EnableNullFPSuppression));
return true;
}
}
// If the expression is not an "lvalue expression", we can still
// track the constraints on its contents.
SVal V = state->getSValAsScalarOrLoc(S, N->getLocationContext());
// If the value came from an inlined function call, we should at least make
// sure that function isn't pruned in our output.
if (const Expr *E = dyn_cast<Expr>(S))
S = E->IgnoreParenCasts();
ReturnVisitor::addVisitorIfNecessary(N, S, report, EnableNullFPSuppression);
// Uncomment this to find cases where we aren't properly getting the
// base value that was dereferenced.
// assert(!V.isUnknownOrUndef());
// Is it a symbolic value?
if (Optional<loc::MemRegionVal> L = V.getAs<loc::MemRegionVal>()) {
// At this point we are dealing with the region's LValue.
// However, if the rvalue is a symbolic region, we should track it as well.
// Try to use the correct type when looking up the value.
SVal RVal;
if (const Expr *E = dyn_cast<Expr>(S))
RVal = state->getRawSVal(L.getValue(), E->getType());
else
RVal = state->getSVal(L->getRegion());
const MemRegion *RegionRVal = RVal.getAsRegion();
report.addVisitor(llvm::make_unique<UndefOrNullArgVisitor>(L->getRegion()));
if (RegionRVal && isa<SymbolicRegion>(RegionRVal)) {
report.markInteresting(RegionRVal);
report.addVisitor(llvm::make_unique<TrackConstraintBRVisitor>(
loc::MemRegionVal(RegionRVal), false));
}
}
return true;
}
const Expr *NilReceiverBRVisitor::getNilReceiver(const Stmt *S,
const ExplodedNode *N) {
const ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(S);
if (!ME)
return nullptr;
if (const Expr *Receiver = ME->getInstanceReceiver()) {
ProgramStateRef state = N->getState();
SVal V = state->getSVal(Receiver, N->getLocationContext());
if (state->isNull(V).isConstrainedTrue())
return Receiver;
}
return nullptr;
}
PathDiagnosticPiece *NilReceiverBRVisitor::VisitNode(const ExplodedNode *N,
const ExplodedNode *PrevN,
BugReporterContext &BRC,
BugReport &BR) {
Optional<PreStmt> P = N->getLocationAs<PreStmt>();
if (!P)
return nullptr;
const Stmt *S = P->getStmt();
const Expr *Receiver = getNilReceiver(S, N);
if (!Receiver)
return nullptr;
llvm::SmallString<256> Buf;
llvm::raw_svector_ostream OS(Buf);
if (const ObjCMessageExpr *ME = dyn_cast<ObjCMessageExpr>(S)) {
OS << "'";
ME->getSelector().print(OS);
OS << "' not called";
}
else {
OS << "No method is called";
}
OS << " because the receiver is nil";
// The receiver was nil, and hence the method was skipped.
// Register a BugReporterVisitor to issue a message telling us how
// the receiver was null.
bugreporter::trackNullOrUndefValue(N, Receiver, BR, /*IsArg*/ false,
/*EnableNullFPSuppression*/ false);
// Issue a message saying that the method was skipped.
PathDiagnosticLocation L(Receiver, BRC.getSourceManager(),
N->getLocationContext());
return new PathDiagnosticEventPiece(L, OS.str());
}
// Registers every VarDecl inside a Stmt with a last store visitor.
void FindLastStoreBRVisitor::registerStatementVarDecls(BugReport &BR,
const Stmt *S,
bool EnableNullFPSuppression) {
const ExplodedNode *N = BR.getErrorNode();
std::deque<const Stmt *> WorkList;
WorkList.push_back(S);
while (!WorkList.empty()) {
const Stmt *Head = WorkList.front();
WorkList.pop_front();
ProgramStateRef state = N->getState();
ProgramStateManager &StateMgr = state->getStateManager();
if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Head)) {
if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
const VarRegion *R =
StateMgr.getRegionManager().getVarRegion(VD, N->getLocationContext());
// What did we load?
SVal V = state->getSVal(S, N->getLocationContext());
if (V.getAs<loc::ConcreteInt>() || V.getAs<nonloc::ConcreteInt>()) {
// Register a new visitor with the BugReport.
BR.addVisitor(llvm::make_unique<FindLastStoreBRVisitor>(
V.castAs<KnownSVal>(), R, EnableNullFPSuppression));
}
}
}
for (const Stmt *SubStmt : Head->children())
WorkList.push_back(SubStmt);
}
}
//===----------------------------------------------------------------------===//
// Visitor that tries to report interesting diagnostics from conditions.
//===----------------------------------------------------------------------===//
/// Return the tag associated with this visitor. This tag will be used
/// to make all PathDiagnosticPieces created by this visitor.
const char *ConditionBRVisitor::getTag() {
return "ConditionBRVisitor";
}
PathDiagnosticPiece *ConditionBRVisitor::VisitNode(const ExplodedNode *N,
const ExplodedNode *Prev,
BugReporterContext &BRC,
BugReport &BR) {
PathDiagnosticPiece *piece = VisitNodeImpl(N, Prev, BRC, BR);
if (piece) {
piece->setTag(getTag());
if (PathDiagnosticEventPiece *ev=dyn_cast<PathDiagnosticEventPiece>(piece))
ev->setPrunable(true, /* override */ false);
}
return piece;
}
PathDiagnosticPiece *ConditionBRVisitor::VisitNodeImpl(const ExplodedNode *N,
const ExplodedNode *Prev,
BugReporterContext &BRC,
BugReport &BR) {
ProgramPoint progPoint = N->getLocation();
ProgramStateRef CurrentState = N->getState();
ProgramStateRef PrevState = Prev->getState();
// Compare the GDMs of the state, because that is where constraints
// are managed. Note that ensure that we only look at nodes that
// were generated by the analyzer engine proper, not checkers.
if (CurrentState->getGDM().getRoot() ==
PrevState->getGDM().getRoot())
return nullptr;
// If an assumption was made on a branch, it should be caught
// here by looking at the state transition.
if (Optional<BlockEdge> BE = progPoint.getAs<BlockEdge>()) {
const CFGBlock *srcBlk = BE->getSrc();
if (const Stmt *term = srcBlk->getTerminator())
return VisitTerminator(term, N, srcBlk, BE->getDst(), BR, BRC);
return nullptr;
}
if (Optional<PostStmt> PS = progPoint.getAs<PostStmt>()) {
// FIXME: Assuming that BugReporter is a GRBugReporter is a layering
// violation.
const std::pair<const ProgramPointTag *, const ProgramPointTag *> &tags =
cast<GRBugReporter>(BRC.getBugReporter()).
getEngine().geteagerlyAssumeBinOpBifurcationTags();
const ProgramPointTag *tag = PS->getTag();
if (tag == tags.first)
return VisitTrueTest(cast<Expr>(PS->getStmt()), true,
BRC, BR, N);
if (tag == tags.second)
return VisitTrueTest(cast<Expr>(PS->getStmt()), false,
BRC, BR, N);
return nullptr;
}
return nullptr;
}
PathDiagnosticPiece *
ConditionBRVisitor::VisitTerminator(const Stmt *Term,
const ExplodedNode *N,
const CFGBlock *srcBlk,
const CFGBlock *dstBlk,
BugReport &R,
BugReporterContext &BRC) {
const Expr *Cond = nullptr;
switch (Term->getStmtClass()) {
default:
return nullptr;
case Stmt::IfStmtClass:
Cond = cast<IfStmt>(Term)->getCond();
break;
case Stmt::ConditionalOperatorClass:
Cond = cast<ConditionalOperator>(Term)->getCond();
break;
}
assert(Cond);
assert(srcBlk->succ_size() == 2);
const bool tookTrue = *(srcBlk->succ_begin()) == dstBlk;
return VisitTrueTest(Cond, tookTrue, BRC, R, N);
}
PathDiagnosticPiece *
ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
bool tookTrue,
BugReporterContext &BRC,
BugReport &R,
const ExplodedNode *N) {
const Expr *Ex = Cond;
while (true) {
Ex = Ex->IgnoreParenCasts();
switch (Ex->getStmtClass()) {
default:
return nullptr;
case Stmt::BinaryOperatorClass:
return VisitTrueTest(Cond, cast<BinaryOperator>(Ex), tookTrue, BRC,
R, N);
case Stmt::DeclRefExprClass:
return VisitTrueTest(Cond, cast<DeclRefExpr>(Ex), tookTrue, BRC,
R, N);
case Stmt::UnaryOperatorClass: {
const UnaryOperator *UO = cast<UnaryOperator>(Ex);
if (UO->getOpcode() == UO_LNot) {
tookTrue = !tookTrue;
Ex = UO->getSubExpr();
continue;
}
return nullptr;
}
}
}
}
bool ConditionBRVisitor::patternMatch(const Expr *Ex, raw_ostream &Out,
BugReporterContext &BRC,
BugReport &report,
const ExplodedNode *N,
Optional<bool> &prunable) {
const Expr *OriginalExpr = Ex;
Ex = Ex->IgnoreParenCasts();
if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(Ex)) {
const bool quotes = isa<VarDecl>(DR->getDecl());
if (quotes) {
Out << '\'';
const LocationContext *LCtx = N->getLocationContext();
const ProgramState *state = N->getState().get();
if (const MemRegion *R = state->getLValue(cast<VarDecl>(DR->getDecl()),
LCtx).getAsRegion()) {
if (report.isInteresting(R))
prunable = false;
else {
const ProgramState *state = N->getState().get();
SVal V = state->getSVal(R);
if (report.isInteresting(V))
prunable = false;
}
}
}
Out << DR->getDecl()->getDeclName().getAsString();
if (quotes)
Out << '\'';
return quotes;
}
if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(Ex)) {
QualType OriginalTy = OriginalExpr->getType();
if (OriginalTy->isPointerType()) {
if (IL->getValue() == 0) {
Out << "null";
return false;
}
}
else if (OriginalTy->isObjCObjectPointerType()) {
if (IL->getValue() == 0) {
Out << "nil";
return false;
}
}
Out << IL->getValue();
return false;
}
return false;
}
PathDiagnosticPiece *
ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
const BinaryOperator *BExpr,
const bool tookTrue,
BugReporterContext &BRC,
BugReport &R,
const ExplodedNode *N) {
bool shouldInvert = false;
Optional<bool> shouldPrune;
SmallString<128> LhsString, RhsString;
{
llvm::raw_svector_ostream OutLHS(LhsString), OutRHS(RhsString);
const bool isVarLHS = patternMatch(BExpr->getLHS(), OutLHS, BRC, R, N,
shouldPrune);
const bool isVarRHS = patternMatch(BExpr->getRHS(), OutRHS, BRC, R, N,
shouldPrune);
shouldInvert = !isVarLHS && isVarRHS;
}
BinaryOperator::Opcode Op = BExpr->getOpcode();
if (BinaryOperator::isAssignmentOp(Op)) {
// For assignment operators, all that we care about is that the LHS
// evaluates to "true" or "false".
return VisitConditionVariable(LhsString, BExpr->getLHS(), tookTrue,
BRC, R, N);
}
// For non-assignment operations, we require that we can understand
// both the LHS and RHS.
if (LhsString.empty() || RhsString.empty() ||
!BinaryOperator::isComparisonOp(Op))
return nullptr;
// Should we invert the strings if the LHS is not a variable name?
SmallString<256> buf;
llvm::raw_svector_ostream Out(buf);
Out << "Assuming " << (shouldInvert ? RhsString : LhsString) << " is ";
// Do we need to invert the opcode?
if (shouldInvert)
switch (Op) {
default: break;
case BO_LT: Op = BO_GT; break;
case BO_GT: Op = BO_LT; break;
case BO_LE: Op = BO_GE; break;
case BO_GE: Op = BO_LE; break;
}
if (!tookTrue)
switch (Op) {
case BO_EQ: Op = BO_NE; break;
case BO_NE: Op = BO_EQ; break;
case BO_LT: Op = BO_GE; break;
case BO_GT: Op = BO_LE; break;
case BO_LE: Op = BO_GT; break;
case BO_GE: Op = BO_LT; break;
default:
return nullptr;
}
switch (Op) {
case BO_EQ:
Out << "equal to ";
break;
case BO_NE:
Out << "not equal to ";
break;
default:
Out << BinaryOperator::getOpcodeStr(Op) << ' ';
break;
}
Out << (shouldInvert ? LhsString : RhsString);
const LocationContext *LCtx = N->getLocationContext();
PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
PathDiagnosticEventPiece *event =
new PathDiagnosticEventPiece(Loc, Out.str());
if (shouldPrune.hasValue())
event->setPrunable(shouldPrune.getValue());
return event;
}
PathDiagnosticPiece *
ConditionBRVisitor::VisitConditionVariable(StringRef LhsString,
const Expr *CondVarExpr,
const bool tookTrue,
BugReporterContext &BRC,
BugReport &report,
const ExplodedNode *N) {
// FIXME: If there's already a constraint tracker for this variable,
// we shouldn't emit anything here (c.f. the double note in
// test/Analysis/inlining/path-notes.c)
SmallString<256> buf;
llvm::raw_svector_ostream Out(buf);
Out << "Assuming " << LhsString << " is ";
QualType Ty = CondVarExpr->getType();
if (Ty->isPointerType())
Out << (tookTrue ? "not null" : "null");
else if (Ty->isObjCObjectPointerType())
Out << (tookTrue ? "not nil" : "nil");
else if (Ty->isBooleanType())
Out << (tookTrue ? "true" : "false");
else if (Ty->isIntegralOrEnumerationType())
Out << (tookTrue ? "non-zero" : "zero");
else
return nullptr;
const LocationContext *LCtx = N->getLocationContext();
PathDiagnosticLocation Loc(CondVarExpr, BRC.getSourceManager(), LCtx);
PathDiagnosticEventPiece *event =
new PathDiagnosticEventPiece(Loc, Out.str());
if (const DeclRefExpr *DR = dyn_cast<DeclRefExpr>(CondVarExpr)) {
if (const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl())) {
const ProgramState *state = N->getState().get();
if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) {
if (report.isInteresting(R))
event->setPrunable(false);
}
}
}
return event;
}
PathDiagnosticPiece *
ConditionBRVisitor::VisitTrueTest(const Expr *Cond,
const DeclRefExpr *DR,
const bool tookTrue,
BugReporterContext &BRC,
BugReport &report,
const ExplodedNode *N) {
const VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl());
if (!VD)
return nullptr;
SmallString<256> Buf;
llvm::raw_svector_ostream Out(Buf);
Out << "Assuming '" << VD->getDeclName() << "' is ";
QualType VDTy = VD->getType();
if (VDTy->isPointerType())
Out << (tookTrue ? "non-null" : "null");
else if (VDTy->isObjCObjectPointerType())
Out << (tookTrue ? "non-nil" : "nil");
else if (VDTy->isScalarType())
Out << (tookTrue ? "not equal to 0" : "0");
else
return nullptr;
const LocationContext *LCtx = N->getLocationContext();
PathDiagnosticLocation Loc(Cond, BRC.getSourceManager(), LCtx);
PathDiagnosticEventPiece *event =
new PathDiagnosticEventPiece(Loc, Out.str());
const ProgramState *state = N->getState().get();
if (const MemRegion *R = state->getLValue(VD, LCtx).getAsRegion()) {
if (report.isInteresting(R))
event->setPrunable(false);
else {
SVal V = state->getSVal(R);
if (report.isInteresting(V))
event->setPrunable(false);
}
}
return event;
}
// FIXME: Copied from ExprEngineCallAndReturn.cpp.
static bool isInStdNamespace(const Decl *D) {
const DeclContext *DC = D->getDeclContext()->getEnclosingNamespaceContext();
const NamespaceDecl *ND = dyn_cast<NamespaceDecl>(DC);
if (!ND)
return false;
while (const NamespaceDecl *Parent = dyn_cast<NamespaceDecl>(ND->getParent()))
ND = Parent;
return ND->isStdNamespace();
}
std::unique_ptr<PathDiagnosticPiece>
LikelyFalsePositiveSuppressionBRVisitor::getEndPath(BugReporterContext &BRC,
const ExplodedNode *N,
BugReport &BR) {
// Here we suppress false positives coming from system headers. This list is
// based on known issues.
ExprEngine &Eng = BRC.getBugReporter().getEngine();
AnalyzerOptions &Options = Eng.getAnalysisManager().options;
const Decl *D = N->getLocationContext()->getDecl();
if (isInStdNamespace(D)) {
// Skip reports within the 'std' namespace. Although these can sometimes be
// the user's fault, we currently don't report them very well, and
// Note that this will not help for any other data structure libraries, like
// TR1, Boost, or llvm/ADT.
if (Options.shouldSuppressFromCXXStandardLibrary()) {
BR.markInvalid(getTag(), nullptr);
return nullptr;
} else {
// If the complete 'std' suppression is not enabled, suppress reports
// from the 'std' namespace that are known to produce false positives.
// The analyzer issues a false use-after-free when std::list::pop_front
// or std::list::pop_back are called multiple times because we cannot
// reason about the internal invariants of the datastructure.
if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
const CXXRecordDecl *CD = MD->getParent();
if (CD->getName() == "list") {
BR.markInvalid(getTag(), nullptr);
return nullptr;
}
}
// The analyzer issues a false positive when the constructor of
// std::__independent_bits_engine from algorithms is used.
if (const CXXConstructorDecl *MD = dyn_cast<CXXConstructorDecl>(D)) {
const CXXRecordDecl *CD = MD->getParent();
if (CD->getName() == "__independent_bits_engine") {
BR.markInvalid(getTag(), nullptr);
return nullptr;
}
}
// The analyzer issues a false positive on
// std::basic_string<uint8_t> v; v.push_back(1);
// and
// std::u16string s; s += u'a';
// because we cannot reason about the internal invariants of the
// datastructure.
for (const LocationContext *LCtx = N->getLocationContext(); LCtx;
LCtx = LCtx->getParent()) {
const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(LCtx->getDecl());
if (!MD)
continue;
const CXXRecordDecl *CD = MD->getParent();
if (CD->getName() == "basic_string") {
BR.markInvalid(getTag(), nullptr);
return nullptr;
}
}
}
}
// Skip reports within the sys/queue.h macros as we do not have the ability to
// reason about data structure shapes.
SourceManager &SM = BRC.getSourceManager();
FullSourceLoc Loc = BR.getLocation(SM).asLocation();
while (Loc.isMacroID()) {
Loc = Loc.getSpellingLoc();
if (SM.getFilename(Loc).endswith("sys/queue.h")) {
BR.markInvalid(getTag(), nullptr);
return nullptr;
}
}
return nullptr;
}
PathDiagnosticPiece *
UndefOrNullArgVisitor::VisitNode(const ExplodedNode *N,
const ExplodedNode *PrevN,
BugReporterContext &BRC,
BugReport &BR) {
ProgramStateRef State = N->getState();
ProgramPoint ProgLoc = N->getLocation();
// We are only interested in visiting CallEnter nodes.
Optional<CallEnter> CEnter = ProgLoc.getAs<CallEnter>();
if (!CEnter)
return nullptr;
// Check if one of the arguments is the region the visitor is tracking.
CallEventManager &CEMgr = BRC.getStateManager().getCallEventManager();
CallEventRef<> Call = CEMgr.getCaller(CEnter->getCalleeContext(), State);
unsigned Idx = 0;
ArrayRef<ParmVarDecl*> parms = Call->parameters();
for (ArrayRef<ParmVarDecl*>::iterator I = parms.begin(), E = parms.end();
I != E; ++I, ++Idx) {
const MemRegion *ArgReg = Call->getArgSVal(Idx).getAsRegion();
// Are we tracking the argument or its subregion?
if ( !ArgReg || (ArgReg != R && !R->isSubRegionOf(ArgReg->StripCasts())))
continue;
// Check the function parameter type.
const ParmVarDecl *ParamDecl = *I;
assert(ParamDecl && "Formal parameter has no decl?");
QualType T = ParamDecl->getType();
if (!(T->isAnyPointerType() || T->isReferenceType())) {
// Function can only change the value passed in by address.
continue;
}
// If it is a const pointer value, the function does not intend to
// change the value.
if (T->getPointeeType().isConstQualified())
continue;
// Mark the call site (LocationContext) as interesting if the value of the
// argument is undefined or '0'/'NULL'.
SVal BoundVal = State->getSVal(R);
if (BoundVal.isUndef() || BoundVal.isZeroConstant()) {
BR.markInteresting(CEnter->getCalleeContext());
return nullptr;
}
}
return nullptr;
}