1 //=-- ExprEngineC.cpp - ExprEngine support for C expressions ----*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This file defines ExprEngine's support for C expressions.
11 //===----------------------------------------------------------------------===//
13 #include "clang/AST/ExprCXX.h"
14 #include "clang/AST/DeclCXX.h"
15 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
16 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
18 using namespace clang;
22 /// Optionally conjure and return a symbol for offset when processing
23 /// an expression \p Expression.
24 /// If \p Other is a location, conjure a symbol for \p Symbol
25 /// (offset) if it is unknown so that memory arithmetic always
26 /// results in an ElementRegion.
27 /// \p Count The number of times the current basic block was visited.
28 static SVal conjureOffsetSymbolOnLocation(
29 SVal Symbol, SVal Other, Expr* Expression, SValBuilder &svalBuilder,
30 unsigned Count, const LocationContext *LCtx) {
31 QualType Ty = Expression->getType();
32 if (Other.getAs<Loc>() &&
33 Ty->isIntegralOrEnumerationType() &&
35 return svalBuilder.conjureSymbolVal(Expression, LCtx, Ty, Count);
40 void ExprEngine::VisitBinaryOperator(const BinaryOperator* B,
42 ExplodedNodeSet &Dst) {
44 Expr *LHS = B->getLHS()->IgnoreParens();
45 Expr *RHS = B->getRHS()->IgnoreParens();
47 // FIXME: Prechecks eventually go in ::Visit().
48 ExplodedNodeSet CheckedSet;
50 getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, B, *this);
52 // With both the LHS and RHS evaluated, process the operation itself.
53 for (ExplodedNodeSet::iterator it=CheckedSet.begin(), ei=CheckedSet.end();
56 ProgramStateRef state = (*it)->getState();
57 const LocationContext *LCtx = (*it)->getLocationContext();
58 SVal LeftV = state->getSVal(LHS, LCtx);
59 SVal RightV = state->getSVal(RHS, LCtx);
61 BinaryOperator::Opcode Op = B->getOpcode();
63 if (Op == BO_Assign) {
64 // EXPERIMENTAL: "Conjured" symbols.
65 // FIXME: Handle structs.
66 if (RightV.isUnknown()) {
67 unsigned Count = currBldrCtx->blockCount();
68 RightV = svalBuilder.conjureSymbolVal(nullptr, B->getRHS(), LCtx,
71 // Simulate the effects of a "store": bind the value of the RHS
72 // to the L-Value represented by the LHS.
73 SVal ExprVal = B->isGLValue() ? LeftV : RightV;
74 evalStore(Tmp2, B, LHS, *it, state->BindExpr(B, LCtx, ExprVal),
79 if (!B->isAssignmentOp()) {
80 StmtNodeBuilder Bldr(*it, Tmp2, *currBldrCtx);
82 if (B->isAdditiveOp()) {
83 // TODO: This can be removed after we enable history tracking with
85 unsigned Count = currBldrCtx->blockCount();
86 RightV = conjureOffsetSymbolOnLocation(
87 RightV, LeftV, RHS, svalBuilder, Count, LCtx);
88 LeftV = conjureOffsetSymbolOnLocation(
89 LeftV, RightV, LHS, svalBuilder, Count, LCtx);
92 // Although we don't yet model pointers-to-members, we do need to make
93 // sure that the members of temporaries have a valid 'this' pointer for
95 if (B->getOpcode() == BO_PtrMemD)
96 state = createTemporaryRegionIfNeeded(state, LCtx, LHS);
98 // Process non-assignments except commas or short-circuited
99 // logical expressions (LAnd and LOr).
100 SVal Result = evalBinOp(state, Op, LeftV, RightV, B->getType());
101 if (!Result.isUnknown()) {
102 state = state->BindExpr(B, LCtx, Result);
104 // If we cannot evaluate the operation escape the operands.
105 state = escapeValues(state, LeftV, PSK_EscapeOther);
106 state = escapeValues(state, RightV, PSK_EscapeOther);
109 Bldr.generateNode(B, *it, state);
113 assert (B->isCompoundAssignmentOp());
117 llvm_unreachable("Invalid opcode for compound assignment.");
118 case BO_MulAssign: Op = BO_Mul; break;
119 case BO_DivAssign: Op = BO_Div; break;
120 case BO_RemAssign: Op = BO_Rem; break;
121 case BO_AddAssign: Op = BO_Add; break;
122 case BO_SubAssign: Op = BO_Sub; break;
123 case BO_ShlAssign: Op = BO_Shl; break;
124 case BO_ShrAssign: Op = BO_Shr; break;
125 case BO_AndAssign: Op = BO_And; break;
126 case BO_XorAssign: Op = BO_Xor; break;
127 case BO_OrAssign: Op = BO_Or; break;
130 // Perform a load (the LHS). This performs the checks for
131 // null dereferences, and so on.
133 SVal location = LeftV;
134 evalLoad(Tmp, B, LHS, *it, state, location);
136 for (ExplodedNodeSet::iterator I = Tmp.begin(), E = Tmp.end(); I != E;
139 state = (*I)->getState();
140 const LocationContext *LCtx = (*I)->getLocationContext();
141 SVal V = state->getSVal(LHS, LCtx);
143 // Get the computation type.
145 cast<CompoundAssignOperator>(B)->getComputationResultType();
146 CTy = getContext().getCanonicalType(CTy);
149 cast<CompoundAssignOperator>(B)->getComputationLHSType();
150 CLHSTy = getContext().getCanonicalType(CLHSTy);
152 QualType LTy = getContext().getCanonicalType(LHS->getType());
155 V = svalBuilder.evalCast(V, CLHSTy, LTy);
157 // Compute the result of the operation.
158 SVal Result = svalBuilder.evalCast(evalBinOp(state, Op, V, RightV, CTy),
161 // EXPERIMENTAL: "Conjured" symbols.
162 // FIXME: Handle structs.
166 if (Result.isUnknown()) {
167 // The symbolic value is actually for the type of the left-hand side
168 // expression, not the computation type, as this is the value the
169 // LValue on the LHS will bind to.
170 LHSVal = svalBuilder.conjureSymbolVal(nullptr, B->getRHS(), LCtx, LTy,
171 currBldrCtx->blockCount());
172 // However, we need to convert the symbol to the computation type.
173 Result = svalBuilder.evalCast(LHSVal, CTy, LTy);
176 // The left-hand side may bind to a different value then the
178 LHSVal = svalBuilder.evalCast(Result, LTy, CTy);
181 // In C++, assignment and compound assignment operators return an
184 state = state->BindExpr(B, LCtx, location);
186 state = state->BindExpr(B, LCtx, Result);
188 evalStore(Tmp2, B, LHS, *I, state, location, LHSVal);
192 // FIXME: postvisits eventually go in ::Visit()
193 getCheckerManager().runCheckersForPostStmt(Dst, Tmp2, B, *this);
196 void ExprEngine::VisitBlockExpr(const BlockExpr *BE, ExplodedNode *Pred,
197 ExplodedNodeSet &Dst) {
199 CanQualType T = getContext().getCanonicalType(BE->getType());
201 const BlockDecl *BD = BE->getBlockDecl();
202 // Get the value of the block itself.
203 SVal V = svalBuilder.getBlockPointer(BD, T,
204 Pred->getLocationContext(),
205 currBldrCtx->blockCount());
207 ProgramStateRef State = Pred->getState();
209 // If we created a new MemRegion for the block, we should explicitly bind
210 // the captured variables.
211 if (const BlockDataRegion *BDR =
212 dyn_cast_or_null<BlockDataRegion>(V.getAsRegion())) {
214 BlockDataRegion::referenced_vars_iterator I = BDR->referenced_vars_begin(),
215 E = BDR->referenced_vars_end();
217 auto CI = BD->capture_begin();
218 auto CE = BD->capture_end();
219 for (; I != E; ++I) {
220 const VarRegion *capturedR = I.getCapturedRegion();
221 const TypedValueRegion *originalR = I.getOriginalRegion();
223 // If the capture had a copy expression, use the result of evaluating
224 // that expression, otherwise use the original value.
225 // We rely on the invariant that the block declaration's capture variables
226 // are a prefix of the BlockDataRegion's referenced vars (which may include
227 // referenced globals, etc.) to enable fast lookup of the capture for a
228 // given referenced var.
229 const Expr *copyExpr = nullptr;
231 assert(CI->getVariable() == capturedR->getDecl());
232 copyExpr = CI->getCopyExpr();
236 if (capturedR != originalR) {
238 const LocationContext *LCtx = Pred->getLocationContext();
240 originalV = State->getSVal(copyExpr, LCtx);
242 originalV = State->getSVal(loc::MemRegionVal(originalR));
244 State = State->bindLoc(loc::MemRegionVal(capturedR), originalV, LCtx);
250 StmtNodeBuilder Bldr(Pred, Tmp, *currBldrCtx);
251 Bldr.generateNode(BE, Pred,
252 State->BindExpr(BE, Pred->getLocationContext(), V),
253 nullptr, ProgramPoint::PostLValueKind);
255 // FIXME: Move all post/pre visits to ::Visit().
256 getCheckerManager().runCheckersForPostStmt(Dst, Tmp, BE, *this);
259 ProgramStateRef ExprEngine::handleLValueBitCast(
260 ProgramStateRef state, const Expr* Ex, const LocationContext* LCtx,
261 QualType T, QualType ExTy, const CastExpr* CastE, StmtNodeBuilder& Bldr,
262 ExplodedNode* Pred) {
263 if (T->isLValueReferenceType()) {
264 assert(!CastE->getType()->isLValueReferenceType());
265 ExTy = getContext().getLValueReferenceType(ExTy);
266 } else if (T->isRValueReferenceType()) {
267 assert(!CastE->getType()->isRValueReferenceType());
268 ExTy = getContext().getRValueReferenceType(ExTy);
270 // Delegate to SValBuilder to process.
271 SVal OrigV = state->getSVal(Ex, LCtx);
272 SVal V = svalBuilder.evalCast(OrigV, T, ExTy);
273 // Negate the result if we're treating the boolean as a signed i1
274 if (CastE->getCastKind() == CK_BooleanToSignedIntegral)
276 state = state->BindExpr(CastE, LCtx, V);
277 if (V.isUnknown() && !OrigV.isUnknown()) {
278 state = escapeValues(state, OrigV, PSK_EscapeOther);
280 Bldr.generateNode(CastE, Pred, state);
285 void ExprEngine::VisitCast(const CastExpr *CastE, const Expr *Ex,
286 ExplodedNode *Pred, ExplodedNodeSet &Dst) {
288 ExplodedNodeSet dstPreStmt;
289 getCheckerManager().runCheckersForPreStmt(dstPreStmt, Pred, CastE, *this);
291 if (CastE->getCastKind() == CK_LValueToRValue ||
292 CastE->getCastKind() == CK_LValueToRValueBitCast) {
293 for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end();
295 ExplodedNode *subExprNode = *I;
296 ProgramStateRef state = subExprNode->getState();
297 const LocationContext *LCtx = subExprNode->getLocationContext();
298 evalLoad(Dst, CastE, CastE, subExprNode, state, state->getSVal(Ex, LCtx));
304 QualType T = CastE->getType();
305 QualType ExTy = Ex->getType();
307 if (const ExplicitCastExpr *ExCast=dyn_cast_or_null<ExplicitCastExpr>(CastE))
308 T = ExCast->getTypeAsWritten();
310 StmtNodeBuilder Bldr(dstPreStmt, Dst, *currBldrCtx);
311 for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end();
315 ProgramStateRef state = Pred->getState();
316 const LocationContext *LCtx = Pred->getLocationContext();
318 switch (CastE->getCastKind()) {
319 case CK_LValueToRValue:
320 case CK_LValueToRValueBitCast:
321 llvm_unreachable("LValueToRValue casts handled earlier.");
324 // The analyzer doesn't do anything special with these casts,
325 // since it understands retain/release semantics already.
326 case CK_ARCProduceObject:
327 case CK_ARCConsumeObject:
328 case CK_ARCReclaimReturnedObject:
329 case CK_ARCExtendBlockObject: // Fall-through.
330 case CK_CopyAndAutoreleaseBlockObject:
331 // The analyser can ignore atomic casts for now, although some future
332 // checkers may want to make certain that you're not modifying the same
333 // value through atomic and nonatomic pointers.
334 case CK_AtomicToNonAtomic:
335 case CK_NonAtomicToAtomic:
338 case CK_ConstructorConversion:
339 case CK_UserDefinedConversion:
340 case CK_FunctionToPointerDecay:
341 case CK_BuiltinFnToFnPtr: {
342 // Copy the SVal of Ex to CastE.
343 ProgramStateRef state = Pred->getState();
344 const LocationContext *LCtx = Pred->getLocationContext();
345 SVal V = state->getSVal(Ex, LCtx);
346 state = state->BindExpr(CastE, LCtx, V);
347 Bldr.generateNode(CastE, Pred, state);
350 case CK_MemberPointerToBoolean:
351 case CK_PointerToBoolean: {
352 SVal V = state->getSVal(Ex, LCtx);
353 auto PTMSV = V.getAs<nonloc::PointerToMember>();
355 V = svalBuilder.makeTruthVal(!PTMSV->isNullMemberPointer(), ExTy);
356 if (V.isUndef() || PTMSV) {
357 state = state->BindExpr(CastE, LCtx, V);
358 Bldr.generateNode(CastE, Pred, state);
361 // Explicitly proceed with default handler for this case cascade.
363 handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
367 case CK_ArrayToPointerDecay:
369 case CK_AddressSpaceConversion:
370 case CK_BooleanToSignedIntegral:
371 case CK_IntegralToPointer:
372 case CK_PointerToIntegral: {
373 SVal V = state->getSVal(Ex, LCtx);
374 if (V.getAs<nonloc::PointerToMember>()) {
375 state = state->BindExpr(CastE, LCtx, UnknownVal());
376 Bldr.generateNode(CastE, Pred, state);
379 // Explicitly proceed with default handler for this case cascade.
381 handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
384 case CK_IntegralToBoolean:
385 case CK_IntegralToFloating:
386 case CK_FloatingToIntegral:
387 case CK_FloatingToBoolean:
388 case CK_FloatingCast:
389 case CK_FloatingRealToComplex:
390 case CK_FloatingComplexToReal:
391 case CK_FloatingComplexToBoolean:
392 case CK_FloatingComplexCast:
393 case CK_FloatingComplexToIntegralComplex:
394 case CK_IntegralRealToComplex:
395 case CK_IntegralComplexToReal:
396 case CK_IntegralComplexToBoolean:
397 case CK_IntegralComplexCast:
398 case CK_IntegralComplexToFloatingComplex:
399 case CK_CPointerToObjCPointerCast:
400 case CK_BlockPointerToObjCPointerCast:
401 case CK_AnyPointerToBlockPointerCast:
402 case CK_ObjCObjectLValueCast:
403 case CK_ZeroToOCLOpaqueType:
404 case CK_IntToOCLSampler:
405 case CK_LValueBitCast:
406 case CK_FloatingToFixedPoint:
407 case CK_FixedPointToFloating:
408 case CK_FixedPointCast:
409 case CK_FixedPointToBoolean:
410 case CK_FixedPointToIntegral:
411 case CK_IntegralToFixedPoint: {
413 handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
416 case CK_IntegralCast: {
417 // Delegate to SValBuilder to process.
418 SVal V = state->getSVal(Ex, LCtx);
419 if (AMgr.options.ShouldSupportSymbolicIntegerCasts)
420 V = svalBuilder.evalCast(V, T, ExTy);
422 V = svalBuilder.evalIntegralCast(state, V, T, ExTy);
423 state = state->BindExpr(CastE, LCtx, V);
424 Bldr.generateNode(CastE, Pred, state);
427 case CK_DerivedToBase:
428 case CK_UncheckedDerivedToBase: {
429 // For DerivedToBase cast, delegate to the store manager.
430 SVal val = state->getSVal(Ex, LCtx);
431 val = getStoreManager().evalDerivedToBase(val, CastE);
432 state = state->BindExpr(CastE, LCtx, val);
433 Bldr.generateNode(CastE, Pred, state);
436 // Handle C++ dyn_cast.
438 SVal val = state->getSVal(Ex, LCtx);
440 // Compute the type of the result.
441 QualType resultType = CastE->getType();
442 if (CastE->isGLValue())
443 resultType = getContext().getPointerType(resultType);
447 // Check if the value being cast does not evaluates to 0.
448 if (!val.isZeroConstant())
449 if (Optional<SVal> V =
450 StateMgr.getStoreManager().evalBaseToDerived(val, T)) {
456 if (T->isReferenceType()) {
457 // A bad_cast exception is thrown if input value is a reference.
458 // Currently, we model this, by generating a sink.
459 Bldr.generateSink(CastE, Pred, state);
462 // If the cast fails on a pointer, bind to 0.
463 state = state->BindExpr(CastE, LCtx, svalBuilder.makeNull());
466 // If we don't know if the cast succeeded, conjure a new symbol.
467 if (val.isUnknown()) {
468 DefinedOrUnknownSVal NewSym =
469 svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType,
470 currBldrCtx->blockCount());
471 state = state->BindExpr(CastE, LCtx, NewSym);
473 // Else, bind to the derived region value.
474 state = state->BindExpr(CastE, LCtx, val);
476 Bldr.generateNode(CastE, Pred, state);
479 case CK_BaseToDerived: {
480 SVal val = state->getSVal(Ex, LCtx);
481 QualType resultType = CastE->getType();
482 if (CastE->isGLValue())
483 resultType = getContext().getPointerType(resultType);
485 if (!val.isConstant()) {
486 Optional<SVal> V = getStoreManager().evalBaseToDerived(val, T);
487 val = V ? *V : UnknownVal();
490 // Failed to cast or the result is unknown, fall back to conservative.
491 if (val.isUnknown()) {
493 svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType,
494 currBldrCtx->blockCount());
496 state = state->BindExpr(CastE, LCtx, val);
497 Bldr.generateNode(CastE, Pred, state);
500 case CK_NullToPointer: {
501 SVal V = svalBuilder.makeNull();
502 state = state->BindExpr(CastE, LCtx, V);
503 Bldr.generateNode(CastE, Pred, state);
506 case CK_NullToMemberPointer: {
507 SVal V = svalBuilder.getMemberPointer(nullptr);
508 state = state->BindExpr(CastE, LCtx, V);
509 Bldr.generateNode(CastE, Pred, state);
512 case CK_DerivedToBaseMemberPointer:
513 case CK_BaseToDerivedMemberPointer:
514 case CK_ReinterpretMemberPointer: {
515 SVal V = state->getSVal(Ex, LCtx);
516 if (auto PTMSV = V.getAs<nonloc::PointerToMember>()) {
518 svalBuilder.makePointerToMember(getBasicVals().accumCXXBase(
519 CastE->path(), *PTMSV, CastE->getCastKind()));
520 state = state->BindExpr(CastE, LCtx, CastedPTMSV);
521 Bldr.generateNode(CastE, Pred, state);
524 // Explicitly proceed with default handler for this case cascade.
527 // Various C++ casts that are not handled yet.
530 case CK_VectorSplat: {
531 QualType resultType = CastE->getType();
532 if (CastE->isGLValue())
533 resultType = getContext().getPointerType(resultType);
534 SVal result = svalBuilder.conjureSymbolVal(
535 /*symbolTag=*/nullptr, CastE, LCtx, resultType,
536 currBldrCtx->blockCount());
537 state = state->BindExpr(CastE, LCtx, result);
538 Bldr.generateNode(CastE, Pred, state);
545 void ExprEngine::VisitCompoundLiteralExpr(const CompoundLiteralExpr *CL,
547 ExplodedNodeSet &Dst) {
548 StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
550 ProgramStateRef State = Pred->getState();
551 const LocationContext *LCtx = Pred->getLocationContext();
553 const Expr *Init = CL->getInitializer();
554 SVal V = State->getSVal(CL->getInitializer(), LCtx);
556 if (isa<CXXConstructExpr, CXXStdInitializerListExpr>(Init)) {
557 // No work needed. Just pass the value up to this expression.
559 assert(isa<InitListExpr>(Init));
560 Loc CLLoc = State->getLValue(CL, LCtx);
561 State = State->bindLoc(CLLoc, V, LCtx);
567 B.generateNode(CL, Pred, State->BindExpr(CL, LCtx, V));
570 void ExprEngine::VisitDeclStmt(const DeclStmt *DS, ExplodedNode *Pred,
571 ExplodedNodeSet &Dst) {
572 if (isa<TypedefNameDecl>(*DS->decl_begin())) {
573 // C99 6.7.7 "Any array size expressions associated with variable length
574 // array declarators are evaluated each time the declaration of the typedef
575 // name is reached in the order of execution."
576 // The checkers should know about typedef to be able to handle VLA size
578 ExplodedNodeSet DstPre;
579 getCheckerManager().runCheckersForPreStmt(DstPre, Pred, DS, *this);
580 getCheckerManager().runCheckersForPostStmt(Dst, DstPre, DS, *this);
584 // Assumption: The CFG has one DeclStmt per Decl.
585 const VarDecl *VD = dyn_cast_or_null<VarDecl>(*DS->decl_begin());
588 //TODO:AZ: remove explicit insertion after refactoring is done.
593 // FIXME: all pre/post visits should eventually be handled by ::Visit().
594 ExplodedNodeSet dstPreVisit;
595 getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, DS, *this);
597 ExplodedNodeSet dstEvaluated;
598 StmtNodeBuilder B(dstPreVisit, dstEvaluated, *currBldrCtx);
599 for (ExplodedNodeSet::iterator I = dstPreVisit.begin(), E = dstPreVisit.end();
601 ExplodedNode *N = *I;
602 ProgramStateRef state = N->getState();
603 const LocationContext *LC = N->getLocationContext();
605 // Decls without InitExpr are not initialized explicitly.
606 if (const Expr *InitEx = VD->getInit()) {
608 // Note in the state that the initialization has occurred.
609 ExplodedNode *UpdatedN = N;
610 SVal InitVal = state->getSVal(InitEx, LC);
612 assert(DS->isSingleDecl());
613 if (getObjectUnderConstruction(state, DS, LC)) {
614 state = finishObjectConstruction(state, DS, LC);
615 // We constructed the object directly in the variable.
616 // No need to bind anything.
617 B.generateNode(DS, UpdatedN, state);
619 // Recover some path-sensitivity if a scalar value evaluated to
621 if (InitVal.isUnknown()) {
622 QualType Ty = InitEx->getType();
623 if (InitEx->isGLValue()) {
624 Ty = getContext().getPointerType(Ty);
627 InitVal = svalBuilder.conjureSymbolVal(nullptr, InitEx, LC, Ty,
628 currBldrCtx->blockCount());
632 B.takeNodes(UpdatedN);
633 ExplodedNodeSet Dst2;
634 evalBind(Dst2, DS, UpdatedN, state->getLValue(VD, LC), InitVal, true);
639 B.generateNode(DS, N, state);
643 getCheckerManager().runCheckersForPostStmt(Dst, B.getResults(), DS, *this);
646 void ExprEngine::VisitLogicalExpr(const BinaryOperator* B, ExplodedNode *Pred,
647 ExplodedNodeSet &Dst) {
648 // This method acts upon CFG elements for logical operators && and ||
649 // and attaches the value (true or false) to them as expressions.
650 // It doesn't produce any state splits.
651 // If we made it that far, we're past the point when we modeled the short
652 // circuit. It means that we should have precise knowledge about whether
653 // we've short-circuited. If we did, we already know the value we need to
654 // bind. If we didn't, the value of the RHS (casted to the boolean type)
656 // Currently this method tries to figure out whether we've short-circuited
657 // by looking at the ExplodedGraph. This method is imperfect because there
658 // could inevitably have been merges that would have resulted in multiple
659 // potential path traversal histories. We bail out when we fail.
660 // Due to this ambiguity, a more reliable solution would have been to
661 // track the short circuit operation history path-sensitively until
662 // we evaluate the respective logical operator.
663 assert(B->getOpcode() == BO_LAnd ||
664 B->getOpcode() == BO_LOr);
666 StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx);
667 ProgramStateRef state = Pred->getState();
669 if (B->getType()->isVectorType()) {
670 // FIXME: We do not model vector arithmetic yet. When adding support for
671 // that, note that the CFG-based reasoning below does not apply, because
672 // logical operators on vectors are not short-circuit. Currently they are
673 // modeled as short-circuit in Clang CFG but this is incorrect.
674 // Do not set the value for the expression. It'd be UnknownVal by default.
675 Bldr.generateNode(B, Pred, state);
679 ExplodedNode *N = Pred;
680 while (!N->getLocation().getAs<BlockEntrance>()) {
681 ProgramPoint P = N->getLocation();
682 assert(P.getAs<PreStmt>()|| P.getAs<PreStmtPurgeDeadSymbols>());
684 if (N->pred_size() != 1) {
685 // We failed to track back where we came from.
686 Bldr.generateNode(B, Pred, state);
689 N = *N->pred_begin();
692 if (N->pred_size() != 1) {
693 // We failed to track back where we came from.
694 Bldr.generateNode(B, Pred, state);
698 N = *N->pred_begin();
699 BlockEdge BE = N->getLocation().castAs<BlockEdge>();
702 // Determine the value of the expression by introspecting how we
703 // got this location in the CFG. This requires looking at the previous
704 // block we were in and what kind of control-flow transfer was involved.
705 const CFGBlock *SrcBlock = BE.getSrc();
706 // The only terminator (if there is one) that makes sense is a logical op.
707 CFGTerminator T = SrcBlock->getTerminator();
708 if (const BinaryOperator *Term = cast_or_null<BinaryOperator>(T.getStmt())) {
710 assert(Term->isLogicalOp());
711 assert(SrcBlock->succ_size() == 2);
712 // Did we take the true or false branch?
713 unsigned constant = (*SrcBlock->succ_begin() == BE.getDst()) ? 1 : 0;
714 X = svalBuilder.makeIntVal(constant, B->getType());
717 // If there is no terminator, by construction the last statement
718 // in SrcBlock is the value of the enclosing expression.
719 // However, we still need to constrain that value to be 0 or 1.
720 assert(!SrcBlock->empty());
721 CFGStmt Elem = SrcBlock->rbegin()->castAs<CFGStmt>();
722 const Expr *RHS = cast<Expr>(Elem.getStmt());
723 SVal RHSVal = N->getState()->getSVal(RHS, Pred->getLocationContext());
725 if (RHSVal.isUndef()) {
728 // We evaluate "RHSVal != 0" expression which result in 0 if the value is
729 // known to be false, 1 if the value is known to be true and a new symbol
730 // when the assumption is unknown.
731 nonloc::ConcreteInt Zero(getBasicVals().getValue(0, B->getType()));
732 X = evalBinOp(N->getState(), BO_NE,
733 svalBuilder.evalCast(RHSVal, B->getType(), RHS->getType()),
737 Bldr.generateNode(B, Pred, state->BindExpr(B, Pred->getLocationContext(), X));
740 void ExprEngine::VisitInitListExpr(const InitListExpr *IE,
742 ExplodedNodeSet &Dst) {
743 StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
745 ProgramStateRef state = Pred->getState();
746 const LocationContext *LCtx = Pred->getLocationContext();
747 QualType T = getContext().getCanonicalType(IE->getType());
748 unsigned NumInitElements = IE->getNumInits();
750 if (!IE->isGLValue() && !IE->isTransparent() &&
751 (T->isArrayType() || T->isRecordType() || T->isVectorType() ||
752 T->isAnyComplexType())) {
753 llvm::ImmutableList<SVal> vals = getBasicVals().getEmptySValList();
755 // Handle base case where the initializer has no elements.
756 // e.g: static int* myArray[] = {};
757 if (NumInitElements == 0) {
758 SVal V = svalBuilder.makeCompoundVal(T, vals);
759 B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V));
763 for (const Stmt *S : llvm::reverse(*IE)) {
764 SVal V = state->getSVal(cast<Expr>(S), LCtx);
765 vals = getBasicVals().prependSVal(V, vals);
768 B.generateNode(IE, Pred,
769 state->BindExpr(IE, LCtx,
770 svalBuilder.makeCompoundVal(T, vals)));
774 // Handle scalars: int{5} and int{} and GLvalues.
775 // Note, if the InitListExpr is a GLvalue, it means that there is an address
776 // representing it, so it must have a single init element.
777 assert(NumInitElements <= 1);
780 if (NumInitElements == 0)
781 V = getSValBuilder().makeZeroVal(T);
783 V = state->getSVal(IE->getInit(0), LCtx);
785 B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V));
788 void ExprEngine::VisitGuardedExpr(const Expr *Ex,
792 ExplodedNodeSet &Dst) {
795 StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
796 ProgramStateRef state = Pred->getState();
797 const LocationContext *LCtx = Pred->getLocationContext();
798 const CFGBlock *SrcBlock = nullptr;
800 // Find the predecessor block.
801 ProgramStateRef SrcState = state;
802 for (const ExplodedNode *N = Pred ; N ; N = *N->pred_begin()) {
803 ProgramPoint PP = N->getLocation();
804 if (PP.getAs<PreStmtPurgeDeadSymbols>() || PP.getAs<BlockEntrance>()) {
805 // If the state N has multiple predecessors P, it means that successors
806 // of P are all equivalent.
807 // In turn, that means that all nodes at P are equivalent in terms
808 // of observable behavior at N, and we can follow any of them.
809 // FIXME: a more robust solution which does not walk up the tree.
812 SrcBlock = PP.castAs<BlockEdge>().getSrc();
813 SrcState = N->getState();
817 assert(SrcBlock && "missing function entry");
819 // Find the last expression in the predecessor block. That is the
820 // expression that is used for the value of the ternary expression.
821 bool hasValue = false;
824 for (CFGElement CE : llvm::reverse(*SrcBlock)) {
825 if (Optional<CFGStmt> CS = CE.getAs<CFGStmt>()) {
826 const Expr *ValEx = cast<Expr>(CS->getStmt());
827 ValEx = ValEx->IgnoreParens();
829 // For GNU extension '?:' operator, the left hand side will be an
830 // OpaqueValueExpr, so get the underlying expression.
831 if (const OpaqueValueExpr *OpaqueEx = dyn_cast<OpaqueValueExpr>(L))
832 L = OpaqueEx->getSourceExpr();
834 // If the last expression in the predecessor block matches true or false
835 // subexpression, get its the value.
836 if (ValEx == L->IgnoreParens() || ValEx == R->IgnoreParens()) {
838 V = SrcState->getSVal(ValEx, LCtx);
845 V = svalBuilder.conjureSymbolVal(nullptr, Ex, LCtx,
846 currBldrCtx->blockCount());
848 // Generate a new node with the binding from the appropriate path.
849 B.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V, true));
853 VisitOffsetOfExpr(const OffsetOfExpr *OOE,
854 ExplodedNode *Pred, ExplodedNodeSet &Dst) {
855 StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
856 Expr::EvalResult Result;
857 if (OOE->EvaluateAsInt(Result, getContext())) {
858 APSInt IV = Result.Val.getInt();
859 assert(IV.getBitWidth() == getContext().getTypeSize(OOE->getType()));
860 assert(OOE->getType()->castAs<BuiltinType>()->isInteger());
861 assert(IV.isSigned() == OOE->getType()->isSignedIntegerType());
862 SVal X = svalBuilder.makeIntVal(IV);
863 B.generateNode(OOE, Pred,
864 Pred->getState()->BindExpr(OOE, Pred->getLocationContext(),
867 // FIXME: Handle the case where __builtin_offsetof is not a constant.
872 VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *Ex,
874 ExplodedNodeSet &Dst) {
875 // FIXME: Prechecks eventually go in ::Visit().
876 ExplodedNodeSet CheckedSet;
877 getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, Ex, *this);
879 ExplodedNodeSet EvalSet;
880 StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx);
882 QualType T = Ex->getTypeOfArgument();
884 for (ExplodedNodeSet::iterator I = CheckedSet.begin(), E = CheckedSet.end();
886 if (Ex->getKind() == UETT_SizeOf) {
887 if (!T->isIncompleteType() && !T->isConstantSizeType()) {
888 assert(T->isVariableArrayType() && "Unknown non-constant-sized type.");
890 // FIXME: Add support for VLA type arguments and VLA expressions.
891 // When that happens, we should probably refactor VLASizeChecker's code.
893 } else if (T->getAs<ObjCObjectType>()) {
894 // Some code tries to take the sizeof an ObjCObjectType, relying that
895 // the compiler has laid out its representation. Just report Unknown
901 APSInt Value = Ex->EvaluateKnownConstInt(getContext());
902 CharUnits amt = CharUnits::fromQuantity(Value.getZExtValue());
904 ProgramStateRef state = (*I)->getState();
905 state = state->BindExpr(Ex, (*I)->getLocationContext(),
906 svalBuilder.makeIntVal(amt.getQuantity(),
908 Bldr.generateNode(Ex, *I, state);
911 getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, Ex, *this);
914 void ExprEngine::handleUOExtension(ExplodedNodeSet::iterator I,
915 const UnaryOperator *U,
916 StmtNodeBuilder &Bldr) {
917 // FIXME: We can probably just have some magic in Environment::getSVal()
918 // that propagates values, instead of creating a new node here.
920 // Unary "+" is a no-op, similar to a parentheses. We still have places
921 // where it may be a block-level expression, so we need to
922 // generate an extra node that just propagates the value of the
924 const Expr *Ex = U->getSubExpr()->IgnoreParens();
925 ProgramStateRef state = (*I)->getState();
926 const LocationContext *LCtx = (*I)->getLocationContext();
927 Bldr.generateNode(U, *I, state->BindExpr(U, LCtx,
928 state->getSVal(Ex, LCtx)));
931 void ExprEngine::VisitUnaryOperator(const UnaryOperator* U, ExplodedNode *Pred,
932 ExplodedNodeSet &Dst) {
933 // FIXME: Prechecks eventually go in ::Visit().
934 ExplodedNodeSet CheckedSet;
935 getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, U, *this);
937 ExplodedNodeSet EvalSet;
938 StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx);
940 for (ExplodedNodeSet::iterator I = CheckedSet.begin(), E = CheckedSet.end();
942 switch (U->getOpcode()) {
946 VisitIncrementDecrementOperator(U, *I, Tmp);
951 const Expr *Ex = U->getSubExpr()->IgnoreParens();
953 // FIXME: We don't have complex SValues yet.
954 if (Ex->getType()->isAnyComplexType()) {
955 // Just report "Unknown."
959 // For all other types, UO_Real is an identity operation.
960 assert (U->getType() == Ex->getType());
961 ProgramStateRef state = (*I)->getState();
962 const LocationContext *LCtx = (*I)->getLocationContext();
963 Bldr.generateNode(U, *I, state->BindExpr(U, LCtx,
964 state->getSVal(Ex, LCtx)));
969 const Expr *Ex = U->getSubExpr()->IgnoreParens();
970 // FIXME: We don't have complex SValues yet.
971 if (Ex->getType()->isAnyComplexType()) {
972 // Just report "Unknown."
975 // For all other types, UO_Imag returns 0.
976 ProgramStateRef state = (*I)->getState();
977 const LocationContext *LCtx = (*I)->getLocationContext();
978 SVal X = svalBuilder.makeZeroVal(Ex->getType());
979 Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, X));
984 // Process pointer-to-member address operation.
985 const Expr *Ex = U->getSubExpr()->IgnoreParens();
986 if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Ex)) {
987 const ValueDecl *VD = DRE->getDecl();
989 if (isa<CXXMethodDecl, FieldDecl, IndirectFieldDecl>(VD)) {
990 ProgramStateRef State = (*I)->getState();
991 const LocationContext *LCtx = (*I)->getLocationContext();
992 SVal SV = svalBuilder.getMemberPointer(cast<NamedDecl>(VD));
993 Bldr.generateNode(U, *I, State->BindExpr(U, LCtx, SV));
997 // Explicitly proceed with default handler for this case cascade.
998 handleUOExtension(I, U, Bldr);
1002 assert(!U->isGLValue());
1005 case UO_Extension: {
1006 handleUOExtension(I, U, Bldr);
1013 assert (!U->isGLValue());
1014 const Expr *Ex = U->getSubExpr()->IgnoreParens();
1015 ProgramStateRef state = (*I)->getState();
1016 const LocationContext *LCtx = (*I)->getLocationContext();
1018 // Get the value of the subexpression.
1019 SVal V = state->getSVal(Ex, LCtx);
1021 if (V.isUnknownOrUndef()) {
1022 Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, V));
1026 switch (U->getOpcode()) {
1028 llvm_unreachable("Invalid Opcode.");
1030 // FIXME: Do we need to handle promotions?
1031 state = state->BindExpr(U, LCtx, evalComplement(V.castAs<NonLoc>()));
1034 // FIXME: Do we need to handle promotions?
1035 state = state->BindExpr(U, LCtx, evalMinus(V.castAs<NonLoc>()));
1038 // C99 6.5.3.3: "The expression !E is equivalent to (0==E)."
1040 // Note: technically we do "E == 0", but this is the same in the
1041 // transfer functions as "0 == E".
1043 if (Optional<Loc> LV = V.getAs<Loc>()) {
1044 Loc X = svalBuilder.makeNullWithType(Ex->getType());
1045 Result = evalBinOp(state, BO_EQ, *LV, X, U->getType());
1046 } else if (Ex->getType()->isFloatingType()) {
1047 // FIXME: handle floating point types.
1048 Result = UnknownVal();
1050 nonloc::ConcreteInt X(getBasicVals().getValue(0, Ex->getType()));
1051 Result = evalBinOp(state, BO_EQ, V.castAs<NonLoc>(), X,
1055 state = state->BindExpr(U, LCtx, Result);
1058 Bldr.generateNode(U, *I, state);
1064 getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, U, *this);
1067 void ExprEngine::VisitIncrementDecrementOperator(const UnaryOperator* U,
1069 ExplodedNodeSet &Dst) {
1070 // Handle ++ and -- (both pre- and post-increment).
1071 assert (U->isIncrementDecrementOp());
1072 const Expr *Ex = U->getSubExpr()->IgnoreParens();
1074 const LocationContext *LCtx = Pred->getLocationContext();
1075 ProgramStateRef state = Pred->getState();
1076 SVal loc = state->getSVal(Ex, LCtx);
1079 ExplodedNodeSet Tmp;
1080 evalLoad(Tmp, U, Ex, Pred, state, loc);
1082 ExplodedNodeSet Dst2;
1083 StmtNodeBuilder Bldr(Tmp, Dst2, *currBldrCtx);
1084 for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end();I!=E;++I) {
1086 state = (*I)->getState();
1087 assert(LCtx == (*I)->getLocationContext());
1088 SVal V2_untested = state->getSVal(Ex, LCtx);
1090 // Propagate unknown and undefined values.
1091 if (V2_untested.isUnknownOrUndef()) {
1092 state = state->BindExpr(U, LCtx, V2_untested);
1094 // Perform the store, so that the uninitialized value detection happens.
1096 ExplodedNodeSet Dst3;
1097 evalStore(Dst3, U, Ex, *I, state, loc, V2_untested);
1098 Bldr.addNodes(Dst3);
1102 DefinedSVal V2 = V2_untested.castAs<DefinedSVal>();
1104 // Handle all other values.
1105 BinaryOperator::Opcode Op = U->isIncrementOp() ? BO_Add : BO_Sub;
1107 // If the UnaryOperator has non-location type, use its type to create the
1108 // constant value. If the UnaryOperator has location type, create the
1109 // constant with int type and pointer width.
1113 if (U->getType()->isAnyPointerType())
1114 RHS = svalBuilder.makeArrayIndex(1);
1115 else if (U->getType()->isIntegralOrEnumerationType())
1116 RHS = svalBuilder.makeIntVal(1, U->getType());
1120 // The use of an operand of type bool with the ++ operators is deprecated
1121 // but valid until C++17. And if the operand of the ++ operator is of type
1122 // bool, it is set to true until C++17. Note that for '_Bool', it is also
1123 // set to true when it encounters ++ operator.
1124 if (U->getType()->isBooleanType() && U->isIncrementOp())
1125 Result = svalBuilder.makeTruthVal(true, U->getType());
1127 Result = evalBinOp(state, Op, V2, RHS, U->getType());
1129 // Conjure a new symbol if necessary to recover precision.
1130 if (Result.isUnknown()){
1131 DefinedOrUnknownSVal SymVal =
1132 svalBuilder.conjureSymbolVal(nullptr, U, LCtx,
1133 currBldrCtx->blockCount());
1136 // If the value is a location, ++/-- should always preserve
1137 // non-nullness. Check if the original value was non-null, and if so
1138 // propagate that constraint.
1139 if (Loc::isLocType(U->getType())) {
1140 DefinedOrUnknownSVal Constraint =
1141 svalBuilder.evalEQ(state, V2,svalBuilder.makeZeroVal(U->getType()));
1143 if (!state->assume(Constraint, true)) {
1144 // It isn't feasible for the original value to be null.
1145 // Propagate this constraint.
1146 Constraint = svalBuilder.evalEQ(state, SymVal,
1147 svalBuilder.makeZeroVal(U->getType()));
1149 state = state->assume(Constraint, false);
1155 // Since the lvalue-to-rvalue conversion is explicit in the AST,
1156 // we bind an l-value if the operator is prefix and an lvalue (in C++).
1158 state = state->BindExpr(U, LCtx, loc);
1160 state = state->BindExpr(U, LCtx, U->isPostfix() ? V2 : Result);
1162 // Perform the store.
1164 ExplodedNodeSet Dst3;
1165 evalStore(Dst3, U, Ex, *I, state, loc, Result);
1166 Bldr.addNodes(Dst3);