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 ProgramStateRef ExprEngine::handleLVectorSplat(
286 ProgramStateRef state, const LocationContext* LCtx, const CastExpr* CastE,
287 StmtNodeBuilder &Bldr, ExplodedNode* Pred) {
288 // Recover some path sensitivity by conjuring a new value.
289 QualType resultType = CastE->getType();
290 if (CastE->isGLValue())
291 resultType = getContext().getPointerType(resultType);
292 SVal result = svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx,
294 currBldrCtx->blockCount());
295 state = state->BindExpr(CastE, LCtx, result);
296 Bldr.generateNode(CastE, Pred, state);
301 void ExprEngine::VisitCast(const CastExpr *CastE, const Expr *Ex,
302 ExplodedNode *Pred, ExplodedNodeSet &Dst) {
304 ExplodedNodeSet dstPreStmt;
305 getCheckerManager().runCheckersForPreStmt(dstPreStmt, Pred, CastE, *this);
307 if (CastE->getCastKind() == CK_LValueToRValue) {
308 for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end();
310 ExplodedNode *subExprNode = *I;
311 ProgramStateRef state = subExprNode->getState();
312 const LocationContext *LCtx = subExprNode->getLocationContext();
313 evalLoad(Dst, CastE, CastE, subExprNode, state, state->getSVal(Ex, LCtx));
319 QualType T = CastE->getType();
320 QualType ExTy = Ex->getType();
322 if (const ExplicitCastExpr *ExCast=dyn_cast_or_null<ExplicitCastExpr>(CastE))
323 T = ExCast->getTypeAsWritten();
325 StmtNodeBuilder Bldr(dstPreStmt, Dst, *currBldrCtx);
326 for (ExplodedNodeSet::iterator I = dstPreStmt.begin(), E = dstPreStmt.end();
330 ProgramStateRef state = Pred->getState();
331 const LocationContext *LCtx = Pred->getLocationContext();
333 switch (CastE->getCastKind()) {
334 case CK_LValueToRValue:
335 llvm_unreachable("LValueToRValue casts handled earlier.");
338 // The analyzer doesn't do anything special with these casts,
339 // since it understands retain/release semantics already.
340 case CK_ARCProduceObject:
341 case CK_ARCConsumeObject:
342 case CK_ARCReclaimReturnedObject:
343 case CK_ARCExtendBlockObject: // Fall-through.
344 case CK_CopyAndAutoreleaseBlockObject:
345 // The analyser can ignore atomic casts for now, although some future
346 // checkers may want to make certain that you're not modifying the same
347 // value through atomic and nonatomic pointers.
348 case CK_AtomicToNonAtomic:
349 case CK_NonAtomicToAtomic:
352 case CK_ConstructorConversion:
353 case CK_UserDefinedConversion:
354 case CK_FunctionToPointerDecay:
355 case CK_BuiltinFnToFnPtr: {
356 // Copy the SVal of Ex to CastE.
357 ProgramStateRef state = Pred->getState();
358 const LocationContext *LCtx = Pred->getLocationContext();
359 SVal V = state->getSVal(Ex, LCtx);
360 state = state->BindExpr(CastE, LCtx, V);
361 Bldr.generateNode(CastE, Pred, state);
364 case CK_MemberPointerToBoolean:
365 case CK_PointerToBoolean: {
366 SVal V = state->getSVal(Ex, LCtx);
367 auto PTMSV = V.getAs<nonloc::PointerToMember>();
369 V = svalBuilder.makeTruthVal(!PTMSV->isNullMemberPointer(), ExTy);
370 if (V.isUndef() || PTMSV) {
371 state = state->BindExpr(CastE, LCtx, V);
372 Bldr.generateNode(CastE, Pred, state);
375 // Explicitly proceed with default handler for this case cascade.
377 handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
381 case CK_ArrayToPointerDecay:
383 case CK_LValueToRValueBitCast:
384 case CK_AddressSpaceConversion:
385 case CK_BooleanToSignedIntegral:
386 case CK_IntegralToPointer:
387 case CK_PointerToIntegral: {
388 SVal V = state->getSVal(Ex, LCtx);
389 if (V.getAs<nonloc::PointerToMember>()) {
390 state = state->BindExpr(CastE, LCtx, UnknownVal());
391 Bldr.generateNode(CastE, Pred, state);
394 // Explicitly proceed with default handler for this case cascade.
396 handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
399 case CK_IntegralToBoolean:
400 case CK_IntegralToFloating:
401 case CK_FloatingToIntegral:
402 case CK_FloatingToBoolean:
403 case CK_FloatingCast:
404 case CK_FloatingRealToComplex:
405 case CK_FloatingComplexToReal:
406 case CK_FloatingComplexToBoolean:
407 case CK_FloatingComplexCast:
408 case CK_FloatingComplexToIntegralComplex:
409 case CK_IntegralRealToComplex:
410 case CK_IntegralComplexToReal:
411 case CK_IntegralComplexToBoolean:
412 case CK_IntegralComplexCast:
413 case CK_IntegralComplexToFloatingComplex:
414 case CK_CPointerToObjCPointerCast:
415 case CK_BlockPointerToObjCPointerCast:
416 case CK_AnyPointerToBlockPointerCast:
417 case CK_ObjCObjectLValueCast:
418 case CK_ZeroToOCLOpaqueType:
419 case CK_IntToOCLSampler:
420 case CK_LValueBitCast:
421 case CK_FixedPointCast:
422 case CK_FixedPointToBoolean:
423 case CK_FixedPointToIntegral:
424 case CK_IntegralToFixedPoint: {
426 handleLValueBitCast(state, Ex, LCtx, T, ExTy, CastE, Bldr, Pred);
429 case CK_IntegralCast: {
430 // Delegate to SValBuilder to process.
431 SVal V = state->getSVal(Ex, LCtx);
432 V = svalBuilder.evalIntegralCast(state, V, T, ExTy);
433 state = state->BindExpr(CastE, LCtx, V);
434 Bldr.generateNode(CastE, Pred, state);
437 case CK_DerivedToBase:
438 case CK_UncheckedDerivedToBase: {
439 // For DerivedToBase cast, delegate to the store manager.
440 SVal val = state->getSVal(Ex, LCtx);
441 val = getStoreManager().evalDerivedToBase(val, CastE);
442 state = state->BindExpr(CastE, LCtx, val);
443 Bldr.generateNode(CastE, Pred, state);
446 // Handle C++ dyn_cast.
448 SVal val = state->getSVal(Ex, LCtx);
450 // Compute the type of the result.
451 QualType resultType = CastE->getType();
452 if (CastE->isGLValue())
453 resultType = getContext().getPointerType(resultType);
457 // Check if the value being cast evaluates to 0.
458 if (val.isZeroConstant())
460 // Else, evaluate the cast.
462 val = getStoreManager().attemptDownCast(val, T, Failed);
465 if (T->isReferenceType()) {
466 // A bad_cast exception is thrown if input value is a reference.
467 // Currently, we model this, by generating a sink.
468 Bldr.generateSink(CastE, Pred, state);
471 // If the cast fails on a pointer, bind to 0.
472 state = state->BindExpr(CastE, LCtx, svalBuilder.makeNull());
475 // If we don't know if the cast succeeded, conjure a new symbol.
476 if (val.isUnknown()) {
477 DefinedOrUnknownSVal NewSym =
478 svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType,
479 currBldrCtx->blockCount());
480 state = state->BindExpr(CastE, LCtx, NewSym);
482 // Else, bind to the derived region value.
483 state = state->BindExpr(CastE, LCtx, val);
485 Bldr.generateNode(CastE, Pred, state);
488 case CK_BaseToDerived: {
489 SVal val = state->getSVal(Ex, LCtx);
490 QualType resultType = CastE->getType();
491 if (CastE->isGLValue())
492 resultType = getContext().getPointerType(resultType);
496 if (!val.isConstant()) {
497 val = getStoreManager().attemptDownCast(val, T, Failed);
500 // Failed to cast or the result is unknown, fall back to conservative.
501 if (Failed || val.isUnknown()) {
503 svalBuilder.conjureSymbolVal(nullptr, CastE, LCtx, resultType,
504 currBldrCtx->blockCount());
506 state = state->BindExpr(CastE, LCtx, val);
507 Bldr.generateNode(CastE, Pred, state);
510 case CK_NullToPointer: {
511 SVal V = svalBuilder.makeNull();
512 state = state->BindExpr(CastE, LCtx, V);
513 Bldr.generateNode(CastE, Pred, state);
516 case CK_NullToMemberPointer: {
517 SVal V = svalBuilder.getMemberPointer(nullptr);
518 state = state->BindExpr(CastE, LCtx, V);
519 Bldr.generateNode(CastE, Pred, state);
522 case CK_DerivedToBaseMemberPointer:
523 case CK_BaseToDerivedMemberPointer:
524 case CK_ReinterpretMemberPointer: {
525 SVal V = state->getSVal(Ex, LCtx);
526 if (auto PTMSV = V.getAs<nonloc::PointerToMember>()) {
527 SVal CastedPTMSV = svalBuilder.makePointerToMember(
528 getBasicVals().accumCXXBase(
529 llvm::make_range<CastExpr::path_const_iterator>(
530 CastE->path_begin(), CastE->path_end()), *PTMSV));
531 state = state->BindExpr(CastE, LCtx, CastedPTMSV);
532 Bldr.generateNode(CastE, Pred, state);
535 // Explicitly proceed with default handler for this case cascade.
536 state = handleLVectorSplat(state, LCtx, CastE, Bldr, Pred);
539 // Various C++ casts that are not handled yet.
541 case CK_VectorSplat: {
542 state = handleLVectorSplat(state, LCtx, CastE, Bldr, Pred);
549 void ExprEngine::VisitCompoundLiteralExpr(const CompoundLiteralExpr *CL,
551 ExplodedNodeSet &Dst) {
552 StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
554 ProgramStateRef State = Pred->getState();
555 const LocationContext *LCtx = Pred->getLocationContext();
557 const Expr *Init = CL->getInitializer();
558 SVal V = State->getSVal(CL->getInitializer(), LCtx);
560 if (isa<CXXConstructExpr>(Init) || isa<CXXStdInitializerListExpr>(Init)) {
561 // No work needed. Just pass the value up to this expression.
563 assert(isa<InitListExpr>(Init));
564 Loc CLLoc = State->getLValue(CL, LCtx);
565 State = State->bindLoc(CLLoc, V, LCtx);
571 B.generateNode(CL, Pred, State->BindExpr(CL, LCtx, V));
574 void ExprEngine::VisitDeclStmt(const DeclStmt *DS, ExplodedNode *Pred,
575 ExplodedNodeSet &Dst) {
576 if (isa<TypedefNameDecl>(*DS->decl_begin())) {
577 // C99 6.7.7 "Any array size expressions associated with variable length
578 // array declarators are evaluated each time the declaration of the typedef
579 // name is reached in the order of execution."
580 // The checkers should know about typedef to be able to handle VLA size
582 ExplodedNodeSet DstPre;
583 getCheckerManager().runCheckersForPreStmt(DstPre, Pred, DS, *this);
584 getCheckerManager().runCheckersForPostStmt(Dst, DstPre, DS, *this);
588 // Assumption: The CFG has one DeclStmt per Decl.
589 const VarDecl *VD = dyn_cast_or_null<VarDecl>(*DS->decl_begin());
592 //TODO:AZ: remove explicit insertion after refactoring is done.
597 // FIXME: all pre/post visits should eventually be handled by ::Visit().
598 ExplodedNodeSet dstPreVisit;
599 getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, DS, *this);
601 ExplodedNodeSet dstEvaluated;
602 StmtNodeBuilder B(dstPreVisit, dstEvaluated, *currBldrCtx);
603 for (ExplodedNodeSet::iterator I = dstPreVisit.begin(), E = dstPreVisit.end();
605 ExplodedNode *N = *I;
606 ProgramStateRef state = N->getState();
607 const LocationContext *LC = N->getLocationContext();
609 // Decls without InitExpr are not initialized explicitly.
610 if (const Expr *InitEx = VD->getInit()) {
612 // Note in the state that the initialization has occurred.
613 ExplodedNode *UpdatedN = N;
614 SVal InitVal = state->getSVal(InitEx, LC);
616 assert(DS->isSingleDecl());
617 if (getObjectUnderConstruction(state, DS, LC)) {
618 state = finishObjectConstruction(state, DS, LC);
619 // We constructed the object directly in the variable.
620 // No need to bind anything.
621 B.generateNode(DS, UpdatedN, state);
623 // Recover some path-sensitivity if a scalar value evaluated to
625 if (InitVal.isUnknown()) {
626 QualType Ty = InitEx->getType();
627 if (InitEx->isGLValue()) {
628 Ty = getContext().getPointerType(Ty);
631 InitVal = svalBuilder.conjureSymbolVal(nullptr, InitEx, LC, Ty,
632 currBldrCtx->blockCount());
636 B.takeNodes(UpdatedN);
637 ExplodedNodeSet Dst2;
638 evalBind(Dst2, DS, UpdatedN, state->getLValue(VD, LC), InitVal, true);
643 B.generateNode(DS, N, state);
647 getCheckerManager().runCheckersForPostStmt(Dst, B.getResults(), DS, *this);
650 void ExprEngine::VisitLogicalExpr(const BinaryOperator* B, ExplodedNode *Pred,
651 ExplodedNodeSet &Dst) {
652 // This method acts upon CFG elements for logical operators && and ||
653 // and attaches the value (true or false) to them as expressions.
654 // It doesn't produce any state splits.
655 // If we made it that far, we're past the point when we modeled the short
656 // circuit. It means that we should have precise knowledge about whether
657 // we've short-circuited. If we did, we already know the value we need to
658 // bind. If we didn't, the value of the RHS (casted to the boolean type)
660 // Currently this method tries to figure out whether we've short-circuited
661 // by looking at the ExplodedGraph. This method is imperfect because there
662 // could inevitably have been merges that would have resulted in multiple
663 // potential path traversal histories. We bail out when we fail.
664 // Due to this ambiguity, a more reliable solution would have been to
665 // track the short circuit operation history path-sensitively until
666 // we evaluate the respective logical operator.
667 assert(B->getOpcode() == BO_LAnd ||
668 B->getOpcode() == BO_LOr);
670 StmtNodeBuilder Bldr(Pred, Dst, *currBldrCtx);
671 ProgramStateRef state = Pred->getState();
673 if (B->getType()->isVectorType()) {
674 // FIXME: We do not model vector arithmetic yet. When adding support for
675 // that, note that the CFG-based reasoning below does not apply, because
676 // logical operators on vectors are not short-circuit. Currently they are
677 // modeled as short-circuit in Clang CFG but this is incorrect.
678 // Do not set the value for the expression. It'd be UnknownVal by default.
679 Bldr.generateNode(B, Pred, state);
683 ExplodedNode *N = Pred;
684 while (!N->getLocation().getAs<BlockEntrance>()) {
685 ProgramPoint P = N->getLocation();
686 assert(P.getAs<PreStmt>()|| P.getAs<PreStmtPurgeDeadSymbols>());
688 if (N->pred_size() != 1) {
689 // We failed to track back where we came from.
690 Bldr.generateNode(B, Pred, state);
693 N = *N->pred_begin();
696 if (N->pred_size() != 1) {
697 // We failed to track back where we came from.
698 Bldr.generateNode(B, Pred, state);
702 N = *N->pred_begin();
703 BlockEdge BE = N->getLocation().castAs<BlockEdge>();
706 // Determine the value of the expression by introspecting how we
707 // got this location in the CFG. This requires looking at the previous
708 // block we were in and what kind of control-flow transfer was involved.
709 const CFGBlock *SrcBlock = BE.getSrc();
710 // The only terminator (if there is one) that makes sense is a logical op.
711 CFGTerminator T = SrcBlock->getTerminator();
712 if (const BinaryOperator *Term = cast_or_null<BinaryOperator>(T.getStmt())) {
714 assert(Term->isLogicalOp());
715 assert(SrcBlock->succ_size() == 2);
716 // Did we take the true or false branch?
717 unsigned constant = (*SrcBlock->succ_begin() == BE.getDst()) ? 1 : 0;
718 X = svalBuilder.makeIntVal(constant, B->getType());
721 // If there is no terminator, by construction the last statement
722 // in SrcBlock is the value of the enclosing expression.
723 // However, we still need to constrain that value to be 0 or 1.
724 assert(!SrcBlock->empty());
725 CFGStmt Elem = SrcBlock->rbegin()->castAs<CFGStmt>();
726 const Expr *RHS = cast<Expr>(Elem.getStmt());
727 SVal RHSVal = N->getState()->getSVal(RHS, Pred->getLocationContext());
729 if (RHSVal.isUndef()) {
732 // We evaluate "RHSVal != 0" expression which result in 0 if the value is
733 // known to be false, 1 if the value is known to be true and a new symbol
734 // when the assumption is unknown.
735 nonloc::ConcreteInt Zero(getBasicVals().getValue(0, B->getType()));
736 X = evalBinOp(N->getState(), BO_NE,
737 svalBuilder.evalCast(RHSVal, B->getType(), RHS->getType()),
741 Bldr.generateNode(B, Pred, state->BindExpr(B, Pred->getLocationContext(), X));
744 void ExprEngine::VisitInitListExpr(const InitListExpr *IE,
746 ExplodedNodeSet &Dst) {
747 StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
749 ProgramStateRef state = Pred->getState();
750 const LocationContext *LCtx = Pred->getLocationContext();
751 QualType T = getContext().getCanonicalType(IE->getType());
752 unsigned NumInitElements = IE->getNumInits();
754 if (!IE->isGLValue() && !IE->isTransparent() &&
755 (T->isArrayType() || T->isRecordType() || T->isVectorType() ||
756 T->isAnyComplexType())) {
757 llvm::ImmutableList<SVal> vals = getBasicVals().getEmptySValList();
759 // Handle base case where the initializer has no elements.
760 // e.g: static int* myArray[] = {};
761 if (NumInitElements == 0) {
762 SVal V = svalBuilder.makeCompoundVal(T, vals);
763 B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V));
767 for (InitListExpr::const_reverse_iterator it = IE->rbegin(),
768 ei = IE->rend(); it != ei; ++it) {
769 SVal V = state->getSVal(cast<Expr>(*it), LCtx);
770 vals = getBasicVals().prependSVal(V, vals);
773 B.generateNode(IE, Pred,
774 state->BindExpr(IE, LCtx,
775 svalBuilder.makeCompoundVal(T, vals)));
779 // Handle scalars: int{5} and int{} and GLvalues.
780 // Note, if the InitListExpr is a GLvalue, it means that there is an address
781 // representing it, so it must have a single init element.
782 assert(NumInitElements <= 1);
785 if (NumInitElements == 0)
786 V = getSValBuilder().makeZeroVal(T);
788 V = state->getSVal(IE->getInit(0), LCtx);
790 B.generateNode(IE, Pred, state->BindExpr(IE, LCtx, V));
793 void ExprEngine::VisitGuardedExpr(const Expr *Ex,
797 ExplodedNodeSet &Dst) {
800 StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
801 ProgramStateRef state = Pred->getState();
802 const LocationContext *LCtx = Pred->getLocationContext();
803 const CFGBlock *SrcBlock = nullptr;
805 // Find the predecessor block.
806 ProgramStateRef SrcState = state;
807 for (const ExplodedNode *N = Pred ; N ; N = *N->pred_begin()) {
808 ProgramPoint PP = N->getLocation();
809 if (PP.getAs<PreStmtPurgeDeadSymbols>() || PP.getAs<BlockEntrance>()) {
810 // If the state N has multiple predecessors P, it means that successors
811 // of P are all equivalent.
812 // In turn, that means that all nodes at P are equivalent in terms
813 // of observable behavior at N, and we can follow any of them.
814 // FIXME: a more robust solution which does not walk up the tree.
817 SrcBlock = PP.castAs<BlockEdge>().getSrc();
818 SrcState = N->getState();
822 assert(SrcBlock && "missing function entry");
824 // Find the last expression in the predecessor block. That is the
825 // expression that is used for the value of the ternary expression.
826 bool hasValue = false;
829 for (CFGElement CE : llvm::reverse(*SrcBlock)) {
830 if (Optional<CFGStmt> CS = CE.getAs<CFGStmt>()) {
831 const Expr *ValEx = cast<Expr>(CS->getStmt());
832 ValEx = ValEx->IgnoreParens();
834 // For GNU extension '?:' operator, the left hand side will be an
835 // OpaqueValueExpr, so get the underlying expression.
836 if (const OpaqueValueExpr *OpaqueEx = dyn_cast<OpaqueValueExpr>(L))
837 L = OpaqueEx->getSourceExpr();
839 // If the last expression in the predecessor block matches true or false
840 // subexpression, get its the value.
841 if (ValEx == L->IgnoreParens() || ValEx == R->IgnoreParens()) {
843 V = SrcState->getSVal(ValEx, LCtx);
850 V = svalBuilder.conjureSymbolVal(nullptr, Ex, LCtx,
851 currBldrCtx->blockCount());
853 // Generate a new node with the binding from the appropriate path.
854 B.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V, true));
858 VisitOffsetOfExpr(const OffsetOfExpr *OOE,
859 ExplodedNode *Pred, ExplodedNodeSet &Dst) {
860 StmtNodeBuilder B(Pred, Dst, *currBldrCtx);
861 Expr::EvalResult Result;
862 if (OOE->EvaluateAsInt(Result, getContext())) {
863 APSInt IV = Result.Val.getInt();
864 assert(IV.getBitWidth() == getContext().getTypeSize(OOE->getType()));
865 assert(OOE->getType()->castAs<BuiltinType>()->isInteger());
866 assert(IV.isSigned() == OOE->getType()->isSignedIntegerType());
867 SVal X = svalBuilder.makeIntVal(IV);
868 B.generateNode(OOE, Pred,
869 Pred->getState()->BindExpr(OOE, Pred->getLocationContext(),
872 // FIXME: Handle the case where __builtin_offsetof is not a constant.
877 VisitUnaryExprOrTypeTraitExpr(const UnaryExprOrTypeTraitExpr *Ex,
879 ExplodedNodeSet &Dst) {
880 // FIXME: Prechecks eventually go in ::Visit().
881 ExplodedNodeSet CheckedSet;
882 getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, Ex, *this);
884 ExplodedNodeSet EvalSet;
885 StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx);
887 QualType T = Ex->getTypeOfArgument();
889 for (ExplodedNodeSet::iterator I = CheckedSet.begin(), E = CheckedSet.end();
891 if (Ex->getKind() == UETT_SizeOf) {
892 if (!T->isIncompleteType() && !T->isConstantSizeType()) {
893 assert(T->isVariableArrayType() && "Unknown non-constant-sized type.");
895 // FIXME: Add support for VLA type arguments and VLA expressions.
896 // When that happens, we should probably refactor VLASizeChecker's code.
898 } else if (T->getAs<ObjCObjectType>()) {
899 // Some code tries to take the sizeof an ObjCObjectType, relying that
900 // the compiler has laid out its representation. Just report Unknown
906 APSInt Value = Ex->EvaluateKnownConstInt(getContext());
907 CharUnits amt = CharUnits::fromQuantity(Value.getZExtValue());
909 ProgramStateRef state = (*I)->getState();
910 state = state->BindExpr(Ex, (*I)->getLocationContext(),
911 svalBuilder.makeIntVal(amt.getQuantity(),
913 Bldr.generateNode(Ex, *I, state);
916 getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, Ex, *this);
919 void ExprEngine::handleUOExtension(ExplodedNodeSet::iterator I,
920 const UnaryOperator *U,
921 StmtNodeBuilder &Bldr) {
922 // FIXME: We can probably just have some magic in Environment::getSVal()
923 // that propagates values, instead of creating a new node here.
925 // Unary "+" is a no-op, similar to a parentheses. We still have places
926 // where it may be a block-level expression, so we need to
927 // generate an extra node that just propagates the value of the
929 const Expr *Ex = U->getSubExpr()->IgnoreParens();
930 ProgramStateRef state = (*I)->getState();
931 const LocationContext *LCtx = (*I)->getLocationContext();
932 Bldr.generateNode(U, *I, state->BindExpr(U, LCtx,
933 state->getSVal(Ex, LCtx)));
936 void ExprEngine::VisitUnaryOperator(const UnaryOperator* U, ExplodedNode *Pred,
937 ExplodedNodeSet &Dst) {
938 // FIXME: Prechecks eventually go in ::Visit().
939 ExplodedNodeSet CheckedSet;
940 getCheckerManager().runCheckersForPreStmt(CheckedSet, Pred, U, *this);
942 ExplodedNodeSet EvalSet;
943 StmtNodeBuilder Bldr(CheckedSet, EvalSet, *currBldrCtx);
945 for (ExplodedNodeSet::iterator I = CheckedSet.begin(), E = CheckedSet.end();
947 switch (U->getOpcode()) {
951 VisitIncrementDecrementOperator(U, *I, Tmp);
956 const Expr *Ex = U->getSubExpr()->IgnoreParens();
958 // FIXME: We don't have complex SValues yet.
959 if (Ex->getType()->isAnyComplexType()) {
960 // Just report "Unknown."
964 // For all other types, UO_Real is an identity operation.
965 assert (U->getType() == Ex->getType());
966 ProgramStateRef state = (*I)->getState();
967 const LocationContext *LCtx = (*I)->getLocationContext();
968 Bldr.generateNode(U, *I, state->BindExpr(U, LCtx,
969 state->getSVal(Ex, LCtx)));
974 const Expr *Ex = U->getSubExpr()->IgnoreParens();
975 // FIXME: We don't have complex SValues yet.
976 if (Ex->getType()->isAnyComplexType()) {
977 // Just report "Unknown."
980 // For all other types, UO_Imag returns 0.
981 ProgramStateRef state = (*I)->getState();
982 const LocationContext *LCtx = (*I)->getLocationContext();
983 SVal X = svalBuilder.makeZeroVal(Ex->getType());
984 Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, X));
989 // Process pointer-to-member address operation.
990 const Expr *Ex = U->getSubExpr()->IgnoreParens();
991 if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Ex)) {
992 const ValueDecl *VD = DRE->getDecl();
994 if (isa<CXXMethodDecl>(VD) || isa<FieldDecl>(VD)) {
995 ProgramStateRef State = (*I)->getState();
996 const LocationContext *LCtx = (*I)->getLocationContext();
997 SVal SV = svalBuilder.getMemberPointer(cast<DeclaratorDecl>(VD));
998 Bldr.generateNode(U, *I, State->BindExpr(U, LCtx, SV));
1002 // Explicitly proceed with default handler for this case cascade.
1003 handleUOExtension(I, U, Bldr);
1007 assert(!U->isGLValue());
1010 case UO_Extension: {
1011 handleUOExtension(I, U, Bldr);
1018 assert (!U->isGLValue());
1019 const Expr *Ex = U->getSubExpr()->IgnoreParens();
1020 ProgramStateRef state = (*I)->getState();
1021 const LocationContext *LCtx = (*I)->getLocationContext();
1023 // Get the value of the subexpression.
1024 SVal V = state->getSVal(Ex, LCtx);
1026 if (V.isUnknownOrUndef()) {
1027 Bldr.generateNode(U, *I, state->BindExpr(U, LCtx, V));
1031 switch (U->getOpcode()) {
1033 llvm_unreachable("Invalid Opcode.");
1035 // FIXME: Do we need to handle promotions?
1036 state = state->BindExpr(U, LCtx, evalComplement(V.castAs<NonLoc>()));
1039 // FIXME: Do we need to handle promotions?
1040 state = state->BindExpr(U, LCtx, evalMinus(V.castAs<NonLoc>()));
1043 // C99 6.5.3.3: "The expression !E is equivalent to (0==E)."
1045 // Note: technically we do "E == 0", but this is the same in the
1046 // transfer functions as "0 == E".
1048 if (Optional<Loc> LV = V.getAs<Loc>()) {
1049 Loc X = svalBuilder.makeNullWithType(Ex->getType());
1050 Result = evalBinOp(state, BO_EQ, *LV, X, U->getType());
1051 } else if (Ex->getType()->isFloatingType()) {
1052 // FIXME: handle floating point types.
1053 Result = UnknownVal();
1055 nonloc::ConcreteInt X(getBasicVals().getValue(0, Ex->getType()));
1056 Result = evalBinOp(state, BO_EQ, V.castAs<NonLoc>(), X,
1060 state = state->BindExpr(U, LCtx, Result);
1063 Bldr.generateNode(U, *I, state);
1069 getCheckerManager().runCheckersForPostStmt(Dst, EvalSet, U, *this);
1072 void ExprEngine::VisitIncrementDecrementOperator(const UnaryOperator* U,
1074 ExplodedNodeSet &Dst) {
1075 // Handle ++ and -- (both pre- and post-increment).
1076 assert (U->isIncrementDecrementOp());
1077 const Expr *Ex = U->getSubExpr()->IgnoreParens();
1079 const LocationContext *LCtx = Pred->getLocationContext();
1080 ProgramStateRef state = Pred->getState();
1081 SVal loc = state->getSVal(Ex, LCtx);
1084 ExplodedNodeSet Tmp;
1085 evalLoad(Tmp, U, Ex, Pred, state, loc);
1087 ExplodedNodeSet Dst2;
1088 StmtNodeBuilder Bldr(Tmp, Dst2, *currBldrCtx);
1089 for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end();I!=E;++I) {
1091 state = (*I)->getState();
1092 assert(LCtx == (*I)->getLocationContext());
1093 SVal V2_untested = state->getSVal(Ex, LCtx);
1095 // Propagate unknown and undefined values.
1096 if (V2_untested.isUnknownOrUndef()) {
1097 state = state->BindExpr(U, LCtx, V2_untested);
1099 // Perform the store, so that the uninitialized value detection happens.
1101 ExplodedNodeSet Dst3;
1102 evalStore(Dst3, U, Ex, *I, state, loc, V2_untested);
1103 Bldr.addNodes(Dst3);
1107 DefinedSVal V2 = V2_untested.castAs<DefinedSVal>();
1109 // Handle all other values.
1110 BinaryOperator::Opcode Op = U->isIncrementOp() ? BO_Add : BO_Sub;
1112 // If the UnaryOperator has non-location type, use its type to create the
1113 // constant value. If the UnaryOperator has location type, create the
1114 // constant with int type and pointer width.
1118 if (U->getType()->isAnyPointerType())
1119 RHS = svalBuilder.makeArrayIndex(1);
1120 else if (U->getType()->isIntegralOrEnumerationType())
1121 RHS = svalBuilder.makeIntVal(1, U->getType());
1125 // The use of an operand of type bool with the ++ operators is deprecated
1126 // but valid until C++17. And if the operand of the ++ operator is of type
1127 // bool, it is set to true until C++17. Note that for '_Bool', it is also
1128 // set to true when it encounters ++ operator.
1129 if (U->getType()->isBooleanType() && U->isIncrementOp())
1130 Result = svalBuilder.makeTruthVal(true, U->getType());
1132 Result = evalBinOp(state, Op, V2, RHS, U->getType());
1134 // Conjure a new symbol if necessary to recover precision.
1135 if (Result.isUnknown()){
1136 DefinedOrUnknownSVal SymVal =
1137 svalBuilder.conjureSymbolVal(nullptr, U, LCtx,
1138 currBldrCtx->blockCount());
1141 // If the value is a location, ++/-- should always preserve
1142 // non-nullness. Check if the original value was non-null, and if so
1143 // propagate that constraint.
1144 if (Loc::isLocType(U->getType())) {
1145 DefinedOrUnknownSVal Constraint =
1146 svalBuilder.evalEQ(state, V2,svalBuilder.makeZeroVal(U->getType()));
1148 if (!state->assume(Constraint, true)) {
1149 // It isn't feasible for the original value to be null.
1150 // Propagate this constraint.
1151 Constraint = svalBuilder.evalEQ(state, SymVal,
1152 svalBuilder.makeZeroVal(U->getType()));
1154 state = state->assume(Constraint, false);
1160 // Since the lvalue-to-rvalue conversion is explicit in the AST,
1161 // we bind an l-value if the operator is prefix and an lvalue (in C++).
1163 state = state->BindExpr(U, LCtx, loc);
1165 state = state->BindExpr(U, LCtx, U->isPostfix() ? V2 : Result);
1167 // Perform the store.
1169 ExplodedNodeSet Dst3;
1170 evalStore(Dst3, U, Ex, *I, state, loc, Result);
1171 Bldr.addNodes(Dst3);