OSchip
/
llvm-project
mirror of https://github.com/THU-DSP-LAB/llvm-project.git
13
0
Fork 6
Code Issues Packages Projects Releases Wiki Activity
llvm-project/clang/lib/StaticAnalyzer/Core/ExprEngineC.cpp

1177 lines
43 KiB
C++
Raw Blame History

//=-- ExprEngineC.cpp - ExprEngine support for C expressions ----*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines ExprEngine's support for C expressions.
//
//===----------------------------------------------------------------------===//
#include "clang/AST/ExprCXX.h"
#include "clang/AST/DeclCXX.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
using namespace clang;
using namespace ento;
using llvm::APSInt;
/// Optionally conjure and return a symbol for offset when processing
/// an expression \p Expression.
/// If \p Other is a location, conjure a symbol for \p Symbol
/// (offset) if it is unknown so that memory arithmetic always
/// results in an ElementRegion.
/// \p Count The number of times the current basic block was visited.
static SVal conjureOffsetSymbolOnLocation(
SVal Symbol, SVal Other, Expr* Expression, SValBuilder &svalBuilder,
unsigned Count, const LocationContext *LCtx) {
QualType Ty = Expression->getType();
if (Other.getAs<Loc>() &&
Ty->isIntegralOrEnumerationType() &&
Symbol.isUnknown()) {
return svalBuilder.conjureSymbolVal(Expression, LCtx, Ty, Count);
}
return Symbol;
}
void ExprEngine::VisitBinaryOperator(const BinaryOperator* B,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
Expr *LHS = B->getLHS()->IgnoreParens();
Expr *RHS = B->getRHS()->IgnoreParens();
// FIXME: Prechecks eventually go in ::Visit().
ExplodedNodeSet CheckedSet;
ExplodedNodeSet Tmp2;
getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, B, *this);
// With both the LHS and RHS evaluated, process the operation itself.
for (ExplodedNodeSet::iterator it=CheckedSet.begin(), ei=CheckedSet.end();
it != ei; ++it) {
ProgramStateRef state = (*it)->getState();
const LocationContext *LCtx = (*it)->getLocationContext();
SVal LeftV = state->getSVal(LHS, LCtx);
SVal RightV = state->getSVal(RHS, LCtx);
BinaryOperator::Opcode Op = B->getOpcode();
if (Op == BO_Assign) {
// EXPERIMENTAL: "Conjured" symbols.
// FIXME: Handle structs.
if (RightV.isUnknown()) {
unsigned Count = currBldrCtx->blockCount();
RightV = svalBuilder.conjureSymbolVal(nullptr, B->getRHS(), LCtx,
Count);
}
// Simulate the effects of a "store": bind the value of the RHS
// to the L-Value represented by the LHS.
SVal ExprVal = B->isGLValue() ? LeftV : RightV;
evalStore(Tmp2, B, LHS, *it, state->BindExpr(B, LCtx, ExprVal),
LeftV, RightV);
continue;
}
if (!B->isAssignmentOp()) {
StmtNodeBuilder Bldr(*it, Tmp2, *currBldrCtx);
if (B->isAdditiveOp()) {
// TODO: This can be removed after we enable history tracking with
// SymSymExpr.
unsigned Count = currBldrCtx->blockCount();
RightV = conjureOffsetSymbolOnLocation(
RightV, LeftV, RHS, svalBuilder, Count, LCtx);
LeftV = conjureOffsetSymbolOnLocation(
LeftV, RightV, LHS, svalBuilder, Count, LCtx);
}
// Although we don't yet model pointers-to-members, we do need to make
// sure that the members of temporaries have a valid 'this' pointer for
// other checks.
if (B->getOpcode() == BO_PtrMemD)
state = createTemporaryRegionIfNeeded(state, LCtx, LHS);
// Process non-assignments except commas or short-circuited
// logical expressions (LAnd and LOr).
SVal Result = evalBinOp(state, Op, LeftV, RightV, B->getType());
if (!Result.isUnknown()) {
state = state->BindExpr(B, LCtx, Result);
} else {
// If we cannot evaluate the operation escape the operands.
state = escapeValues(state, LeftV, PSK_EscapeOther);
state = escapeValues(state, RightV, PSK_EscapeOther);
}
Bldr.generateNode(B, *it, state);
continue;
}
assert (B->isCompoundAssignmentOp());
switch (Op) {
default:
llvm_unreachable("Invalid opcode for compound assignment.");
case BO_MulAssign: Op = BO_Mul; break;
case BO_DivAssign: Op = BO_Div; break;
case BO_RemAssign: Op = BO_Rem; break;
case BO_AddAssign: Op = BO_Add; break;
case BO_SubAssign: Op = BO_Sub; break;
case BO_ShlAssign: Op = BO_Shl; break;
case BO_ShrAssign: Op = BO_Shr; break;
case BO_AndAssign: Op = BO_And; break;
case BO_XorAssign: Op = BO_Xor; break;
case BO_OrAssign: Op = BO_Or; break;
}
// Perform a load (the LHS). This performs the checks for
// null dereferences, and so on.
ExplodedNodeSet Tmp;
SVal location = LeftV;
evalLoad(Tmp, B, LHS, *it, state, location);
for (ExplodedNodeSet::iterator I = Tmp.begin(), E = Tmp.end(); I != E;
++I) {
state = (*I)->getState();
const LocationContext *LCtx = (*I)->getLocationContext();
SVal V = state->getSVal(LHS, LCtx);
// Get the computation type.
QualType CTy =
cast<CompoundAssignOperator>(B)->getComputationResultType();
CTy = getContext().getCanonicalType(CTy);
QualType CLHSTy =
cast<CompoundAssignOperator>(B)->getComputationLHSType();
CLHSTy = getContext().getCanonicalType(CLHSTy);
QualType LTy = getContext().getCanonicalType(LHS->getType());
// Promote LHS.
V = svalBuilder.evalCast(V, CLHSTy, LTy);
// Compute the result of the operation.
SVal Result = svalBuilder.evalCast(evalBinOp(state, Op, V, RightV, CTy),
B->getType(), CTy);
// EXPERIMENTAL: "Conjured" symbols.
// FIXME: Handle structs.
SVal LHSVal;
if (Result.isUnknown()) {
// The symbolic value is actually for the type of the left-hand side
// expression, not the computation type, as this is the value the
// LValue on the LHS will bind to.
LHSVal = svalBuilder.conjureSymbolVal(nullptr, B->getRHS(), LCtx, LTy,
currBldrCtx->blockCount());
// However, we need to convert the symbol to the computation type.
Result = svalBuilder.evalCast(LHSVal, CTy, LTy);
}
else {
// The left-hand side may bind to a different value then the
// computation type.
LHSVal = svalBuilder.evalCast(Result, LTy, CTy);
}
// In C++, assignment and compound assignment operators return an
// lvalue.
if (B->isGLValue())
state = state->BindExpr(B, LCtx, location);
else
state = state->BindExpr(B, LCtx, Result);
evalStore(Tmp2, B, LHS, *I, state, location, LHSVal);
}
}
// FIXME: postvisits eventually go in ::Visit()
getCheckerManager().runCheckersForPostStmt(Dst, Tmp2, B, *this);
}
void ExprEngine::VisitBlockExpr(const BlockExpr *BE, ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
CanQualType T = getContext().getCanonicalType(BE->getType());
const BlockDecl *BD = BE->getBlockDecl();
// Get the value of the block itself.
SVal V = svalBuilder.getBlockPointer(BD, T,
Pred->getLocationContext(),
currBldrCtx->blockCount());
ProgramStateRef State = Pred->getState();
// If we created a new MemRegion for the block, we should explicitly bind
// the captured variables.
if (const BlockDataRegion *BDR =
dyn_cast_or_null<BlockDataRegion>(V.getAsRegion())) {
BlockDataRegion::referenced_vars_iterator I = BDR->referenced_vars_begin(),
E = BDR->referenced_vars_end();
auto CI = BD->capture_begin();
auto CE = BD->capture_end();
for (; I != E; ++I) {
const VarRegion *capturedR = I.getCapturedRegion();
const TypedValueRegion *originalR = I.getOriginalRegion();
// If the capture had a copy expression, use the result of evaluating
// that expression, otherwise use the original value.
// We rely on the invariant that the block declaration's capture variables
// are a prefix of the BlockDataRegion's referenced vars (which may include
// referenced globals, etc.) to enable fast lookup of the capture for a
// given referenced var.
const Expr *copyExpr = nullptr;
if (CI != CE) {
assert(CI->getVariable() == capturedR->getDecl());
copyExpr = CI->getCopyExpr();
CI++;
}
if (capturedR != originalR) {
SVal originalV;
const LocationContext *LCtx = Pred->getLocationContext();
if (copyExpr) {
originalV = State->getSVal(copyExpr, LCtx);
} else {
originalV = State->getSVal(loc::MemRegionVal(originalR));
}
State = State->bindLoc(loc::MemRegionVal(capturedR), originalV, LCtx);
}
}
}
ExplodedNodeSet Tmp;
StmtNodeBuilder Bldr(Pred, Tmp, *currBldrCtx);
Bldr.generateNode(BE, Pred,
State->BindExpr(BE, Pred->getLocationContext(), V),
nullptr, ProgramPoint::PostLValueKind);
// FIXME: Move all post/pre visits to ::Visit().
getCheckerManager().runCheckersForPostStmt(Dst, Tmp, BE, *this);
}
ProgramStateRef ExprEngine::handleLValueBitCast(
ProgramStateRef state, const Expr* Ex, const LocationContext* LCtx,
QualType T, QualType ExTy, const CastExpr* CastE, StmtNodeBuilder& Bldr,
ExplodedNode* Pred) {
if (T->isLValueReferenceType()) {
assert(!CastE->getType()->isLValueReferenceType());
ExTy = getContext().getLValueReferenceType(ExTy);
} else if (T->isRValueReferenceType()) {
assert(!CastE->getType()->isRValueReferenceType());
ExTy = getContext().getRValueReferenceType(ExTy);
}
// Delegate to SValBuilder to process.
SVal OrigV = state->getSVal(Ex, LCtx);
SVal V = svalBuilder.evalCast(OrigV, T, ExTy);
// Negate the result if we're treating the boolean as a signed i1
if (CastE->getCastKind() == CK_BooleanToSignedIntegral)
V = evalMinus(V);
state = state->BindExpr(CastE, LCtx, V);
if (V.isUnknown() && !OrigV.isUnknown()) {
state = escapeValues(state, OrigV, PSK_EscapeOther);
}
Bldr.generateNode(CastE, Pred, state);
return state;
}
ProgramStateRef ExprEngine::handleLVectorSplat(
ProgramStateRef state, const LocationContext* LCtx, const CastExpr* CastE,
StmtNodeBuilder &Bldr, ExplodedNode* Pred) {
// Recover some path sensitivity by conjuring a new value.
QualType resultType = CastE->getType();
if (CastE->isGLValue())
resultType = getContext().getPointerType(resultType);
SVal result = svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx,
resultType,
currBldrCtx->blockCount());
state = state->BindExpr(CastE, LCtx, result);
Bldr.generateNode(CastE, Pred, state);
return state;
}
void ExprEngine::VisitCast(const CastExpr *CastE, const Expr *Ex,
ExplodedNode *Pred, ExplodedNodeSet &Dst) {
ExplodedNodeSet dstPreStmt;
getCheckerManager().runCheckersForPreStmt(dstPreStmt, Pred, CastE, *this);
if (CastE->getCastKind() == CK_LValueToRValue) {
for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end();
I!=E; ++I) {
ExplodedNode *subExprNode = *I;
ProgramStateRef state = subExprNode->getState();
const LocationContext *LCtx = subExprNode->getLocationContext();
evalLoad(Dst, CastE, CastE, subExprNode, state, state->getSVal(Ex, LCtx));
}
return;
}
// All other casts.
QualType T = CastE->getType();
QualType ExTy = Ex->getType();
if (const ExplicitCastExpr *ExCast=dyn_cast_or_null<ExplicitCastExpr>(CastE))
T = ExCast->getTypeAsWritten();
StmtNodeBuilder Bldr(dstPreStmt, Dst, *currBldrCtx);
for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end();
I != E; ++I) {
Pred = *I;
ProgramStateRef state = Pred->getState();
const LocationContext *LCtx = Pred->getLocationContext();
switch (CastE->getCastKind()) {
case CK_LValueToRValue:
llvm_unreachable("LValueToRValue casts handled earlier.");
case CK_ToVoid:
continue;
// The analyzer doesn't do anything special with these casts,
// since it understands retain/release semantics already.
case CK_ARCProduceObject:
case CK_ARCConsumeObject:
case CK_ARCReclaimReturnedObject:
case CK_ARCExtendBlockObject: // Fall-through.
case CK_CopyAndAutoreleaseBlockObject:
// The analyser can ignore atomic casts for now, although some future
// checkers may want to make certain that you're not modifying the same
// value through atomic and nonatomic pointers.
case CK_AtomicToNonAtomic:
case CK_NonAtomicToAtomic:
// True no-ops.
case CK_NoOp:
case CK_ConstructorConversion:
case CK_UserDefinedConversion:
case CK_FunctionToPointerDecay:
case CK_BuiltinFnToFnPtr: {
// Copy the SVal of Ex to CastE.
ProgramStateRef state = Pred->getState();
const LocationContext *LCtx = Pred->getLocationContext();
SVal V = state->getSVal(Ex, LCtx);
state = state->BindExpr(CastE, LCtx, V);
Bldr.generateNode(CastE, Pred, state);
continue;
}
case CK_MemberPointerToBoolean:
case CK_PointerToBoolean: {
SVal V = state->getSVal(Ex, LCtx);
auto PTMSV = V.getAs<nonloc::PointerToMember>();
if (PTMSV)
V = svalBuilder.makeTruthVal(!PTMSV->isNullMemberPointer(), ExTy);
if (V.isUndef() || PTMSV) {
state = state->BindExpr(CastE, LCtx, V);
Bldr.generateNode(CastE, Pred, state);
continue;
}
// Explicitly proceed with default handler for this case cascade.
state =
handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
continue;
}
case CK_Dependent:
case CK_ArrayToPointerDecay:
case CK_BitCast:
case CK_LValueToRValueBitCast:
case CK_AddressSpaceConversion:
case CK_BooleanToSignedIntegral:
case CK_IntegralToPointer:
case CK_PointerToIntegral: {
SVal V = state->getSVal(Ex, LCtx);
if (V.getAs<nonloc::PointerToMember>()) {
state = state->BindExpr(CastE, LCtx, UnknownVal());
Bldr.generateNode(CastE, Pred, state);
continue;
}
// Explicitly proceed with default handler for this case cascade.
state =
handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
continue;
}
case CK_IntegralToBoolean:
case CK_IntegralToFloating:
case CK_FloatingToIntegral:
case CK_FloatingToBoolean:
case CK_FloatingCast:
case CK_FloatingRealToComplex:
case CK_FloatingComplexToReal:
case CK_FloatingComplexToBoolean:
case CK_FloatingComplexCast:
case CK_FloatingComplexToIntegralComplex:
case CK_IntegralRealToComplex:
case CK_IntegralComplexToReal:
case CK_IntegralComplexToBoolean:
case CK_IntegralComplexCast:
case CK_IntegralComplexToFloatingComplex:
case CK_CPointerToObjCPointerCast:
case CK_BlockPointerToObjCPointerCast:
case CK_AnyPointerToBlockPointerCast:
case CK_ObjCObjectLValueCast:
case CK_ZeroToOCLOpaqueType:
case CK_IntToOCLSampler:
case CK_LValueBitCast:
case CK_FloatingToFixedPoint:
case CK_FixedPointToFloating:
case CK_FixedPointCast:
case CK_FixedPointToBoolean:
case CK_FixedPointToIntegral:
case CK_IntegralToFixedPoint: {
state =
handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
continue;
}
case CK_IntegralCast: {
// Delegate to SValBuilder to process.
SVal V = state->getSVal(Ex, LCtx);
V = svalBuilder.evalIntegralCast(state, V, T, ExTy);
state = state->BindExpr(CastE, LCtx, V);
Bldr.generateNode(CastE, Pred, state);
continue;
}
case CK_DerivedToBase:
case CK_UncheckedDerivedToBase: {
// For DerivedToBase cast, delegate to the store manager.
SVal val = state->getSVal(Ex, LCtx);
val = getStoreManager().evalDerivedToBase(val, CastE);
state = state->BindExpr(CastE, LCtx, val);
Bldr.generateNode(CastE, Pred, state);
continue;
}
// Handle C++ dyn_cast.
case CK_Dynamic: {
SVal val = state->getSVal(Ex, LCtx);
// Compute the type of the result.
QualType resultType = CastE->getType();
if (CastE->isGLValue())
resultType = getContext().getPointerType(resultType);
bool Failed = false;
// Check if the value being cast evaluates to 0.
if (val.isZeroConstant())
Failed = true;
// Else, evaluate the cast.
else
val = getStoreManager().attemptDownCast(val, T, Failed);
if (Failed) {
if (T->isReferenceType()) {
// A bad_cast exception is thrown if input value is a reference.
// Currently, we model this, by generating a sink.
Bldr.generateSink(CastE, Pred, state);
continue;
} else {
// If the cast fails on a pointer, bind to 0.
state = state->BindExpr(CastE, LCtx, svalBuilder.makeNull());
}
} else {
// If we don't know if the cast succeeded, conjure a new symbol.
if (val.isUnknown()) {
DefinedOrUnknownSVal NewSym =
svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType,
currBldrCtx->blockCount());
state = state->BindExpr(CastE, LCtx, NewSym);
} else
// Else, bind to the derived region value.
state = state->BindExpr(CastE, LCtx, val);
}
Bldr.generateNode(CastE, Pred, state);
continue;
}
case CK_BaseToDerived: {
SVal val = state->getSVal(Ex, LCtx);
QualType resultType = CastE->getType();
if (CastE->isGLValue())
resultType = getContext().getPointerType(resultType);
bool Failed = false;
if (!val.isConstant()) {
val = getStoreManager().attemptDownCast(val, T, Failed);
}
// Failed to cast or the result is unknown, fall back to conservative.
if (Failed || val.isUnknown()) {
val =
svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType,
currBldrCtx->blockCount());
}
state = state->BindExpr(CastE, LCtx, val);
Bldr.generateNode(CastE, Pred, state);
continue;
}
case CK_NullToPointer: {
SVal V = svalBuilder.makeNull();
state = state->BindExpr(CastE, LCtx, V);
Bldr.generateNode(CastE, Pred, state);
continue;
}
case CK_NullToMemberPointer: {
SVal V = svalBuilder.getMemberPointer(nullptr);
state = state->BindExpr(CastE, LCtx, V);
Bldr.generateNode(CastE, Pred, state);
continue;
}
case CK_DerivedToBaseMemberPointer:
case CK_BaseToDerivedMemberPointer:
case CK_ReinterpretMemberPointer: {
SVal V = state->getSVal(Ex, LCtx);
if (auto PTMSV = V.getAs<nonloc::PointerToMember>()) {
SVal CastedPTMSV =
svalBuilder.makePointerToMember(getBasicVals().accumCXXBase(
CastE->path(), *PTMSV, CastE->getCastKind()));
state = state->BindExpr(CastE, LCtx, CastedPTMSV);
Bldr.generateNode(CastE, Pred, state);
continue;
}
// Explicitly proceed with default handler for this case cascade.
state = handleLVectorSplat(state, LCtx, CastE, Bldr, Pred);
continue;
}
// Various C++ casts that are not handled yet.
case CK_ToUnion:
case CK_VectorSplat: {
state = handleLVectorSplat(state, LCtx, CastE, Bldr, Pred);
continue;
}
}
}
}
void ExprEngine::VisitCompoundLiteralExpr(const CompoundLiteralExpr *CL,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
ProgramStateRef State = Pred->getState();
const LocationContext *LCtx = Pred->getLocationContext();
const Expr *Init = CL->getInitializer();
SVal V = State->getSVal(CL->getInitializer(), LCtx);
if (isa<CXXConstructExpr>(Init) || isa<CXXStdInitializerListExpr>(Init)) {
// No work needed. Just pass the value up to this expression.
} else {
assert(isa<InitListExpr>(Init));
Loc CLLoc = State->getLValue(CL, LCtx);
State = State->bindLoc(CLLoc, V, LCtx);
if (CL->isGLValue())
V = CLLoc;
}
B.generateNode(CL, Pred, State->BindExpr(CL, LCtx, V));
}
void ExprEngine::VisitDeclStmt(const DeclStmt *DS, ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
if (isa<TypedefNameDecl>(*DS->decl_begin())) {
// C99 6.7.7 "Any array size expressions associated with variable length
// array declarators are evaluated each time the declaration of the typedef
// name is reached in the order of execution."
// The checkers should know about typedef to be able to handle VLA size
// expressions.
ExplodedNodeSet DstPre;
getCheckerManager().runCheckersForPreStmt(DstPre, Pred, DS, *this);
getCheckerManager().runCheckersForPostStmt(Dst, DstPre, DS, *this);
return;
}
// Assumption: The CFG has one DeclStmt per Decl.
const VarDecl *VD = dyn_cast_or_null<VarDecl>(*DS->decl_begin());
if (!VD) {
//TODO:AZ: remove explicit insertion after refactoring is done.
Dst.insert(Pred);
return;
}
// FIXME: all pre/post visits should eventually be handled by ::Visit().
ExplodedNodeSet dstPreVisit;
getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, DS, *this);
ExplodedNodeSet dstEvaluated;
StmtNodeBuilder B(dstPreVisit, dstEvaluated, *currBldrCtx);
for (ExplodedNodeSet::iterator I = dstPreVisit.begin(), E = dstPreVisit.end();
I!=E; ++I) {
ExplodedNode *N = *I;
ProgramStateRef state = N->getState();
const LocationContext *LC = N->getLocationContext();
// Decls without InitExpr are not initialized explicitly.
if (const Expr *InitEx = VD->getInit()) {
// Note in the state that the initialization has occurred.
ExplodedNode *UpdatedN = N;
SVal InitVal = state->getSVal(InitEx, LC);
assert(DS->isSingleDecl());
if (getObjectUnderConstruction(state, DS, LC)) {
state = finishObjectConstruction(state, DS, LC);
// We constructed the object directly in the variable.
// No need to bind anything.
B.generateNode(DS, UpdatedN, state);
} else {
// Recover some path-sensitivity if a scalar value evaluated to
// UnknownVal.
if (InitVal.isUnknown()) {
QualType Ty = InitEx->getType();
if (InitEx->isGLValue()) {
Ty = getContext().getPointerType(Ty);
}
InitVal = svalBuilder.conjureSymbolVal(nullptr, InitEx, LC, Ty,
currBldrCtx->blockCount());
}
B.takeNodes(UpdatedN);
ExplodedNodeSet Dst2;
evalBind(Dst2, DS, UpdatedN, state->getLValue(VD, LC), InitVal, true);
B.addNodes(Dst2);
}
}
else {
B.generateNode(DS, N, state);
}
}
getCheckerManager().runCheckersForPostStmt(Dst, B.getResults(), DS, *this);
}
void ExprEngine::VisitLogicalExpr(const BinaryOperator* B, ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
// This method acts upon CFG elements for logical operators && and ||
// and attaches the value (true or false) to them as expressions.
// It doesn't produce any state splits.
// If we made it that far, we're past the point when we modeled the short
// circuit. It means that we should have precise knowledge about whether
// we've short-circuited. If we did, we already know the value we need to
// bind. If we didn't, the value of the RHS (casted to the boolean type)
// is the answer.
// Currently this method tries to figure out whether we've short-circuited
// by looking at the ExplodedGraph. This method is imperfect because there
// could inevitably have been merges that would have resulted in multiple
// potential path traversal histories. We bail out when we fail.
// Due to this ambiguity, a more reliable solution would have been to
// track the short circuit operation history path-sensitively until
// we evaluate the respective logical operator.
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;
if (N->pred_size() != 1) {
// We failed to track back where we came from.
Bldr.generateNode(B, Pred, state);
return;
}
N = *N->pred_begin();
}
if (N->pred_size() != 1) {
// We failed to track back where we came from.
Bldr.generateNode(B, Pred, state);
return;
}
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));
}
void ExprEngine::VisitInitListExpr(const InitListExpr *IE,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
ProgramStateRef state = Pred->getState();
const LocationContext *LCtx = Pred->getLocationContext();
QualType T = getContext().getCanonicalType(IE->getType());
unsigned NumInitElements = IE->getNumInits();
if (!IE->isGLValue() && !IE->isTransparent() &&
(T->isArrayType() || T->isRecordType() || T->isVectorType() ||
T->isAnyComplexType())) {
llvm::ImmutableList<SVal> vals = getBasicVals().getEmptySValList();
// Handle base case where the initializer has no elements.
// e.g: static int* myArray[] = {};
if (NumInitElements == 0) {
SVal V = svalBuilder.makeCompoundVal(T, vals);
B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V));
return;
}
for (InitListExpr::const_reverse_iterator it = IE->rbegin(),
ei = IE->rend(); it != ei; ++it) {
SVal V = state->getSVal(cast<Expr>(*it), LCtx);
vals = getBasicVals().prependSVal(V, vals);
}
B.generateNode(IE, Pred,
state->BindExpr(IE, LCtx,
svalBuilder.makeCompoundVal(T, vals)));
return;
}
// Handle scalars: int{5} and int{} and GLvalues.
// Note, if the InitListExpr is a GLvalue, it means that there is an address
// representing it, so it must have a single init element.
assert(NumInitElements <= 1);
SVal V;
if (NumInitElements == 0)
V = getSValBuilder().makeZeroVal(T);
else
V = state->getSVal(IE->getInit(0), LCtx);
B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V));
}
void ExprEngine::VisitGuardedExpr(const Expr *Ex,
const Expr *L,
const Expr *R,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
assert(L && R);
StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
ProgramStateRef state = Pred->getState();
const LocationContext *LCtx = Pred->getLocationContext();
const CFGBlock *SrcBlock = nullptr;
// Find the predecessor block.
ProgramStateRef SrcState = state;
for (const ExplodedNode *N = Pred ; N ; N = *N->pred_begin()) {
ProgramPoint PP = N->getLocation();
if (PP.getAs<PreStmtPurgeDeadSymbols>() || PP.getAs<BlockEntrance>()) {
// If the state N has multiple predecessors P, it means that successors
// of P are all equivalent.
// In turn, that means that all nodes at P are equivalent in terms
// of observable behavior at N, and we can follow any of them.
// FIXME: a more robust solution which does not walk up the tree.
continue;
}
SrcBlock = PP.castAs<BlockEdge>().getSrc();
SrcState = N->getState();
break;
}
assert(SrcBlock && "missing function entry");
// Find the last expression in the predecessor block. That is the
// expression that is used for the value of the ternary expression.
bool hasValue = false;
SVal V;
for (CFGElement CE : llvm::reverse(*SrcBlock)) {
if (Optional<CFGStmt> CS = CE.getAs<CFGStmt>()) {
const Expr *ValEx = cast<Expr>(CS->getStmt());
ValEx = ValEx->IgnoreParens();
// For GNU extension '?:' operator, the left hand side will be an
// OpaqueValueExpr, so get the underlying expression.
if (const OpaqueValueExpr *OpaqueEx = dyn_cast<OpaqueValueExpr>(L))
L = OpaqueEx->getSourceExpr();
// If the last expression in the predecessor block matches true or false
// subexpression, get its the value.
if (ValEx == L->IgnoreParens() || ValEx == R->IgnoreParens()) {
hasValue = true;
V = SrcState->getSVal(ValEx, LCtx);
}
break;
}
}
if (!hasValue)
V = svalBuilder.conjureSymbolVal(nullptr, Ex, LCtx,
currBldrCtx->blockCount());
// Generate a new node with the binding from the appropriate path.
B.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V, true));
}
void ExprEngine::
VisitOffsetOfExpr(const OffsetOfExpr *OOE,
ExplodedNode *Pred, ExplodedNodeSet &Dst) {
StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
Expr::EvalResult Result;
if (OOE->EvaluateAsInt(Result, getContext())) {
APSInt IV = Result.Val.getInt();
assert(IV.getBitWidth() == getContext().getTypeSize(OOE->getType()));
assert(OOE->getType()->castAs<BuiltinType>()->isInteger());
assert(IV.isSigned() == OOE->getType()->isSignedIntegerType());
SVal X = svalBuilder.makeIntVal(IV);
B.generateNode(OOE, Pred,
Pred->getState()->BindExpr(OOE, Pred->getLocationContext(),
X));
}
// FIXME: Handle the case where __builtin_offsetof is not a constant.
}
void ExprEngine::
VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *Ex,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
// FIXME: Prechecks eventually go in ::Visit().
ExplodedNodeSet CheckedSet;
getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, Ex, *this);
ExplodedNodeSet EvalSet;
StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx);
QualType T = Ex->getTypeOfArgument();
for (ExplodedNodeSet::iterator I = CheckedSet.begin(), E = CheckedSet.end();
I != E; ++I) {
if (Ex->getKind() == UETT_SizeOf) {
if (!T->isIncompleteType() && !T->isConstantSizeType()) {
assert(T->isVariableArrayType() && "Unknown non-constant-sized type.");
// FIXME: Add support for VLA type arguments and VLA expressions.
// When that happens, we should probably refactor VLASizeChecker's code.
continue;
} else if (T->getAs<ObjCObjectType>()) {
// Some code tries to take the sizeof an ObjCObjectType, relying that
// the compiler has laid out its representation. Just report Unknown
// for these.
continue;
}
}
APSInt Value = Ex->EvaluateKnownConstInt(getContext());
CharUnits amt = CharUnits::fromQuantity(Value.getZExtValue());
ProgramStateRef state = (*I)->getState();
state = state->BindExpr(Ex, (*I)->getLocationContext(),
svalBuilder.makeIntVal(amt.getQuantity(),
Ex->getType()));
Bldr.generateNode(Ex, *I, state);
}
getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, Ex, *this);
}
void ExprEngine::handleUOExtension(ExplodedNodeSet::iterator I,
const UnaryOperator *U,
StmtNodeBuilder &Bldr) {
// FIXME: We can probably just have some magic in Environment::getSVal()
// that propagates values, instead of creating a new node here.
//
// Unary "+" is a no-op, similar to a parentheses. We still have places
// where it may be a block-level expression, so we need to
// generate an extra node that just propagates the value of the
// subexpression.
const Expr *Ex = U->getSubExpr()->IgnoreParens();
ProgramStateRef state = (*I)->getState();
const LocationContext *LCtx = (*I)->getLocationContext();
Bldr.generateNode(U, *I, state->BindExpr(U, LCtx,
state->getSVal(Ex, LCtx)));
}
void ExprEngine::VisitUnaryOperator(const UnaryOperator* U, ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
// FIXME: Prechecks eventually go in ::Visit().
ExplodedNodeSet CheckedSet;
getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, U, *this);
ExplodedNodeSet EvalSet;
StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx);
for (ExplodedNodeSet::iterator I = CheckedSet.begin(), E = CheckedSet.end();
I != E; ++I) {
switch (U->getOpcode()) {
default: {
Bldr.takeNodes(*I);
ExplodedNodeSet Tmp;
VisitIncrementDecrementOperator(U, *I, Tmp);
Bldr.addNodes(Tmp);
break;
}
case UO_Real: {
const Expr *Ex = U->getSubExpr()->IgnoreParens();
// FIXME: We don't have complex SValues yet.
if (Ex->getType()->isAnyComplexType()) {
// Just report "Unknown."
break;
}
// For all other types, UO_Real is an identity operation.
assert (U->getType() == Ex->getType());
ProgramStateRef state = (*I)->getState();
const LocationContext *LCtx = (*I)->getLocationContext();
Bldr.generateNode(U, *I, state->BindExpr(U, LCtx,
state->getSVal(Ex, LCtx)));
break;
}
case UO_Imag: {
const Expr *Ex = U->getSubExpr()->IgnoreParens();
// FIXME: We don't have complex SValues yet.
if (Ex->getType()->isAnyComplexType()) {
// Just report "Unknown."
break;
}
// For all other types, UO_Imag returns 0.
ProgramStateRef state = (*I)->getState();
const LocationContext *LCtx = (*I)->getLocationContext();
SVal X = svalBuilder.makeZeroVal(Ex->getType());
Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, X));
break;
}
case UO_AddrOf: {
// Process pointer-to-member address operation.
const Expr *Ex = U->getSubExpr()->IgnoreParens();
if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Ex)) {
const ValueDecl *VD = DRE->getDecl();
if (isa<CXXMethodDecl>(VD) || isa<FieldDecl>(VD) ||
isa<IndirectFieldDecl>(VD)) {
ProgramStateRef State = (*I)->getState();
const LocationContext *LCtx = (*I)->getLocationContext();
SVal SV = svalBuilder.getMemberPointer(cast<NamedDecl>(VD));
Bldr.generateNode(U, *I, State->BindExpr(U, LCtx, SV));
break;
}
}
// Explicitly proceed with default handler for this case cascade.
handleUOExtension(I, U, Bldr);
break;
}
case UO_Plus:
assert(!U->isGLValue());
LLVM_FALLTHROUGH;
case UO_Deref:
case UO_Extension: {
handleUOExtension(I, U, Bldr);
break;
}
case UO_LNot:
case UO_Minus:
case UO_Not: {
assert (!U->isGLValue());
const Expr *Ex = U->getSubExpr()->IgnoreParens();
ProgramStateRef state = (*I)->getState();
const LocationContext *LCtx = (*I)->getLocationContext();
// Get the value of the subexpression.
SVal V = state->getSVal(Ex, LCtx);
if (V.isUnknownOrUndef()) {
Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, V));
break;
}
switch (U->getOpcode()) {
default:
llvm_unreachable("Invalid Opcode.");
case UO_Not:
// FIXME: Do we need to handle promotions?
state = state->BindExpr(U, LCtx, evalComplement(V.castAs<NonLoc>()));
break;
case UO_Minus:
// FIXME: Do we need to handle promotions?
state = state->BindExpr(U, LCtx, evalMinus(V.castAs<NonLoc>()));
break;
case UO_LNot:
// C99 6.5.3.3: "The expression !E is equivalent to (0==E)."
//
// Note: technically we do "E == 0", but this is the same in the
// transfer functions as "0 == E".
SVal Result;
if (Optional<Loc> LV = V.getAs<Loc>()) {
Loc X = svalBuilder.makeNullWithType(Ex->getType());
Result = evalBinOp(state, BO_EQ, *LV, X, U->getType());
} else if (Ex->getType()->isFloatingType()) {
// FIXME: handle floating point types.
Result = UnknownVal();
} else {
nonloc::ConcreteInt X(getBasicVals().getValue(0, Ex->getType()));
Result = evalBinOp(state, BO_EQ, V.castAs<NonLoc>(), X,
U->getType());
}
state = state->BindExpr(U, LCtx, Result);
break;
}
Bldr.generateNode(U, *I, state);
break;
}
}
}
getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, U, *this);
}
void ExprEngine::VisitIncrementDecrementOperator(const UnaryOperator* U,
ExplodedNode *Pred,
ExplodedNodeSet &Dst) {
// Handle ++ and -- (both pre- and post-increment).
assert (U->isIncrementDecrementOp());
const Expr *Ex = U->getSubExpr()->IgnoreParens();
const LocationContext *LCtx = Pred->getLocationContext();
ProgramStateRef state = Pred->getState();
SVal loc = state->getSVal(Ex, LCtx);
// Perform a load.
ExplodedNodeSet Tmp;
evalLoad(Tmp, U, Ex, Pred, state, loc);
ExplodedNodeSet Dst2;
StmtNodeBuilder Bldr(Tmp, Dst2, *currBldrCtx);
for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end();I!=E;++I) {
state = (*I)->getState();
assert(LCtx == (*I)->getLocationContext());
SVal V2_untested = state->getSVal(Ex, LCtx);
// Propagate unknown and undefined values.
if (V2_untested.isUnknownOrUndef()) {
state = state->BindExpr(U, LCtx, V2_untested);
// Perform the store, so that the uninitialized value detection happens.
Bldr.takeNodes(*I);
ExplodedNodeSet Dst3;
evalStore(Dst3, U, Ex, *I, state, loc, V2_untested);
Bldr.addNodes(Dst3);
continue;
}
DefinedSVal V2 = V2_untested.castAs<DefinedSVal>();
// Handle all other values.
BinaryOperator::Opcode Op = U->isIncrementOp() ? BO_Add : BO_Sub;
// If the UnaryOperator has non-location type, use its type to create the
// constant value. If the UnaryOperator has location type, create the
// constant with int type and pointer width.
SVal RHS;
SVal Result;
if (U->getType()->isAnyPointerType())
RHS = svalBuilder.makeArrayIndex(1);
else if (U->getType()->isIntegralOrEnumerationType())
RHS = svalBuilder.makeIntVal(1, U->getType());
else
RHS = UnknownVal();
// The use of an operand of type bool with the ++ operators is deprecated
// but valid until C++17. And if the operand of the ++ operator is of type
// bool, it is set to true until C++17. Note that for '_Bool', it is also
// set to true when it encounters ++ operator.
if (U->getType()->isBooleanType() && U->isIncrementOp())
Result = svalBuilder.makeTruthVal(true, U->getType());
else
Result = evalBinOp(state, Op, V2, RHS, U->getType());
// Conjure a new symbol if necessary to recover precision.
if (Result.isUnknown()){
DefinedOrUnknownSVal SymVal =
svalBuilder.conjureSymbolVal(nullptr, U, LCtx,
currBldrCtx->blockCount());
Result = SymVal;
// If the value is a location, ++/-- should always preserve
// non-nullness. Check if the original value was non-null, and if so
// propagate that constraint.
if (Loc::isLocType(U->getType())) {
DefinedOrUnknownSVal Constraint =
svalBuilder.evalEQ(state, V2,svalBuilder.makeZeroVal(U->getType()));
if (!state->assume(Constraint, true)) {
// It isn't feasible for the original value to be null.
// Propagate this constraint.
Constraint = svalBuilder.evalEQ(state, SymVal,
svalBuilder.makeZeroVal(U->getType()));
state = state->assume(Constraint, false);
assert(state);
}
}
}
// Since the lvalue-to-rvalue conversion is explicit in the AST,
// we bind an l-value if the operator is prefix and an lvalue (in C++).
if (U->isGLValue())
state = state->BindExpr(U, LCtx, loc);
else
state = state->BindExpr(U, LCtx, U->isPostfix() ? V2 : Result);
// Perform the store.
Bldr.takeNodes(*I);
ExplodedNodeSet Dst3;
evalStore(Dst3, U, Ex, *I, state, loc, Result);
Bldr.addNodes(Dst3);
}
Dst.insert(Dst2);
}
Reference in New Issue View Git Blame Copy Permalink