1 //==- UninitializedValues.cpp - Find Uninitialized Values -------*- C++ --*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements uninitialized values analysis for source-level CFGs.
12 //===----------------------------------------------------------------------===//
14 #include "clang/AST/ASTContext.h"
15 #include "clang/AST/Attr.h"
16 #include "clang/AST/Decl.h"
17 #include "clang/AST/StmtVisitor.h"
18 #include "clang/Analysis/Analyses/PostOrderCFGView.h"
19 #include "clang/Analysis/Analyses/UninitializedValues.h"
20 #include "clang/Analysis/AnalysisContext.h"
21 #include "clang/Analysis/CFG.h"
22 #include "clang/Analysis/DomainSpecific/ObjCNoReturn.h"
23 #include "llvm/ADT/DenseMap.h"
24 #include "llvm/ADT/Optional.h"
25 #include "llvm/ADT/PackedVector.h"
26 #include "llvm/ADT/SmallBitVector.h"
27 #include "llvm/ADT/SmallVector.h"
28 #include "llvm/Support/SaveAndRestore.h"
31 using namespace clang;
33 #define DEBUG_LOGGING 0
35 static bool isTrackedVar(const VarDecl *vd, const DeclContext *dc) {
36 if (vd->isLocalVarDecl() && !vd->hasGlobalStorage() &&
37 !vd->isExceptionVariable() && !vd->isInitCapture() &&
38 vd->getDeclContext() == dc) {
39 QualType ty = vd->getType();
40 return ty->isScalarType() || ty->isVectorType();
45 //------------------------------------------------------------------------====//
46 // DeclToIndex: a mapping from Decls we track to value indices.
47 //====------------------------------------------------------------------------//
51 llvm::DenseMap<const VarDecl *, unsigned> map;
55 /// Compute the actual mapping from declarations to bits.
56 void computeMap(const DeclContext &dc);
58 /// Return the number of declarations in the map.
59 unsigned size() const { return map.size(); }
61 /// Returns the bit vector index for a given declaration.
62 Optional<unsigned> getValueIndex(const VarDecl *d) const;
66 void DeclToIndex::computeMap(const DeclContext &dc) {
68 DeclContext::specific_decl_iterator<VarDecl> I(dc.decls_begin()),
70 for ( ; I != E; ++I) {
71 const VarDecl *vd = *I;
72 if (isTrackedVar(vd, &dc))
77 Optional<unsigned> DeclToIndex::getValueIndex(const VarDecl *d) const {
78 llvm::DenseMap<const VarDecl *, unsigned>::const_iterator I = map.find(d);
84 //------------------------------------------------------------------------====//
85 // CFGBlockValues: dataflow values for CFG blocks.
86 //====------------------------------------------------------------------------//
88 // These values are defined in such a way that a merge can be done using
90 enum Value { Unknown = 0x0, /* 00 */
91 Initialized = 0x1, /* 01 */
92 Uninitialized = 0x2, /* 10 */
93 MayUninitialized = 0x3 /* 11 */ };
95 static bool isUninitialized(const Value v) {
96 return v >= Uninitialized;
98 static bool isAlwaysUninit(const Value v) {
99 return v == Uninitialized;
104 typedef llvm::PackedVector<Value, 2, llvm::SmallBitVector> ValueVector;
106 class CFGBlockValues {
108 SmallVector<ValueVector, 8> vals;
110 DeclToIndex declToIndex;
112 CFGBlockValues(const CFG &cfg);
114 unsigned getNumEntries() const { return declToIndex.size(); }
116 void computeSetOfDeclarations(const DeclContext &dc);
117 ValueVector &getValueVector(const CFGBlock *block) {
118 return vals[block->getBlockID()];
121 void setAllScratchValues(Value V);
122 void mergeIntoScratch(ValueVector const &source, bool isFirst);
123 bool updateValueVectorWithScratch(const CFGBlock *block);
125 bool hasNoDeclarations() const {
126 return declToIndex.size() == 0;
131 ValueVector::reference operator[](const VarDecl *vd);
133 Value getValue(const CFGBlock *block, const CFGBlock *dstBlock,
135 const Optional<unsigned> &idx = declToIndex.getValueIndex(vd);
136 assert(idx.hasValue());
137 return getValueVector(block)[idx.getValue()];
140 } // end anonymous namespace
142 CFGBlockValues::CFGBlockValues(const CFG &c) : cfg(c), vals(0) {}
144 void CFGBlockValues::computeSetOfDeclarations(const DeclContext &dc) {
145 declToIndex.computeMap(dc);
146 unsigned decls = declToIndex.size();
147 scratch.resize(decls);
148 unsigned n = cfg.getNumBlockIDs();
152 for (unsigned i = 0; i < n; ++i)
153 vals[i].resize(decls);
157 static void printVector(const CFGBlock *block, ValueVector &bv,
159 llvm::errs() << block->getBlockID() << " :";
160 for (unsigned i = 0; i < bv.size(); ++i) {
161 llvm::errs() << ' ' << bv[i];
163 llvm::errs() << " : " << num << '\n';
167 void CFGBlockValues::setAllScratchValues(Value V) {
168 for (unsigned I = 0, E = scratch.size(); I != E; ++I)
172 void CFGBlockValues::mergeIntoScratch(ValueVector const &source,
180 bool CFGBlockValues::updateValueVectorWithScratch(const CFGBlock *block) {
181 ValueVector &dst = getValueVector(block);
182 bool changed = (dst != scratch);
186 printVector(block, scratch, 0);
191 void CFGBlockValues::resetScratch() {
195 ValueVector::reference CFGBlockValues::operator[](const VarDecl *vd) {
196 const Optional<unsigned> &idx = declToIndex.getValueIndex(vd);
197 assert(idx.hasValue());
198 return scratch[idx.getValue()];
201 //------------------------------------------------------------------------====//
202 // Worklist: worklist for dataflow analysis.
203 //====------------------------------------------------------------------------//
206 class DataflowWorklist {
207 PostOrderCFGView::iterator PO_I, PO_E;
208 SmallVector<const CFGBlock *, 20> worklist;
209 llvm::BitVector enqueuedBlocks;
211 DataflowWorklist(const CFG &cfg, PostOrderCFGView &view)
212 : PO_I(view.begin()), PO_E(view.end()),
213 enqueuedBlocks(cfg.getNumBlockIDs(), true) {
214 // Treat the first block as already analyzed.
216 assert(*PO_I == &cfg.getEntry());
217 enqueuedBlocks[(*PO_I)->getBlockID()] = false;
222 void enqueueSuccessors(const CFGBlock *block);
223 const CFGBlock *dequeue();
227 void DataflowWorklist::enqueueSuccessors(const clang::CFGBlock *block) {
228 for (CFGBlock::const_succ_iterator I = block->succ_begin(),
229 E = block->succ_end(); I != E; ++I) {
230 const CFGBlock *Successor = *I;
231 if (!Successor || enqueuedBlocks[Successor->getBlockID()])
233 worklist.push_back(Successor);
234 enqueuedBlocks[Successor->getBlockID()] = true;
238 const CFGBlock *DataflowWorklist::dequeue() {
239 const CFGBlock *B = nullptr;
241 // First dequeue from the worklist. This can represent
242 // updates along backedges that we want propagated as quickly as possible.
243 if (!worklist.empty())
244 B = worklist.pop_back_val();
246 // Next dequeue from the initial reverse post order. This is the
247 // theoretical ideal in the presence of no back edges.
248 else if (PO_I != PO_E) {
256 assert(enqueuedBlocks[B->getBlockID()] == true);
257 enqueuedBlocks[B->getBlockID()] = false;
261 //------------------------------------------------------------------------====//
262 // Classification of DeclRefExprs as use or initialization.
263 //====------------------------------------------------------------------------//
266 class FindVarResult {
268 const DeclRefExpr *dr;
270 FindVarResult(const VarDecl *vd, const DeclRefExpr *dr) : vd(vd), dr(dr) {}
272 const DeclRefExpr *getDeclRefExpr() const { return dr; }
273 const VarDecl *getDecl() const { return vd; }
276 static const Expr *stripCasts(ASTContext &C, const Expr *Ex) {
278 Ex = Ex->IgnoreParenNoopCasts(C);
279 if (const CastExpr *CE = dyn_cast<CastExpr>(Ex)) {
280 if (CE->getCastKind() == CK_LValueBitCast) {
281 Ex = CE->getSubExpr();
290 /// If E is an expression comprising a reference to a single variable, find that
292 static FindVarResult findVar(const Expr *E, const DeclContext *DC) {
293 if (const DeclRefExpr *DRE =
294 dyn_cast<DeclRefExpr>(stripCasts(DC->getParentASTContext(), E)))
295 if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
296 if (isTrackedVar(VD, DC))
297 return FindVarResult(VD, DRE);
298 return FindVarResult(nullptr, nullptr);
301 /// \brief Classify each DeclRefExpr as an initialization or a use. Any
302 /// DeclRefExpr which isn't explicitly classified will be assumed to have
303 /// escaped the analysis and will be treated as an initialization.
304 class ClassifyRefs : public StmtVisitor<ClassifyRefs> {
314 const DeclContext *DC;
315 llvm::DenseMap<const DeclRefExpr*, Class> Classification;
317 bool isTrackedVar(const VarDecl *VD) const {
318 return ::isTrackedVar(VD, DC);
321 void classify(const Expr *E, Class C);
324 ClassifyRefs(AnalysisDeclContext &AC) : DC(cast<DeclContext>(AC.getDecl())) {}
326 void VisitDeclStmt(DeclStmt *DS);
327 void VisitUnaryOperator(UnaryOperator *UO);
328 void VisitBinaryOperator(BinaryOperator *BO);
329 void VisitCallExpr(CallExpr *CE);
330 void VisitCastExpr(CastExpr *CE);
332 void operator()(Stmt *S) { Visit(S); }
334 Class get(const DeclRefExpr *DRE) const {
335 llvm::DenseMap<const DeclRefExpr*, Class>::const_iterator I
336 = Classification.find(DRE);
337 if (I != Classification.end())
340 const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl());
341 if (!VD || !isTrackedVar(VD))
349 static const DeclRefExpr *getSelfInitExpr(VarDecl *VD) {
350 if (Expr *Init = VD->getInit()) {
351 const DeclRefExpr *DRE
352 = dyn_cast<DeclRefExpr>(stripCasts(VD->getASTContext(), Init));
353 if (DRE && DRE->getDecl() == VD)
359 void ClassifyRefs::classify(const Expr *E, Class C) {
360 // The result of a ?: could also be an lvalue.
361 E = E->IgnoreParens();
362 if (const ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E)) {
363 const Expr *TrueExpr = CO->getTrueExpr();
364 if (!isa<OpaqueValueExpr>(TrueExpr))
365 classify(TrueExpr, C);
366 classify(CO->getFalseExpr(), C);
370 FindVarResult Var = findVar(E, DC);
371 if (const DeclRefExpr *DRE = Var.getDeclRefExpr())
372 Classification[DRE] = std::max(Classification[DRE], C);
375 void ClassifyRefs::VisitDeclStmt(DeclStmt *DS) {
376 for (auto *DI : DS->decls()) {
377 VarDecl *VD = dyn_cast<VarDecl>(DI);
378 if (VD && isTrackedVar(VD))
379 if (const DeclRefExpr *DRE = getSelfInitExpr(VD))
380 Classification[DRE] = SelfInit;
384 void ClassifyRefs::VisitBinaryOperator(BinaryOperator *BO) {
385 // Ignore the evaluation of a DeclRefExpr on the LHS of an assignment. If this
386 // is not a compound-assignment, we will treat it as initializing the variable
387 // when TransferFunctions visits it. A compound-assignment does not affect
388 // whether a variable is uninitialized, and there's no point counting it as a
390 if (BO->isCompoundAssignmentOp())
391 classify(BO->getLHS(), Use);
392 else if (BO->getOpcode() == BO_Assign)
393 classify(BO->getLHS(), Ignore);
396 void ClassifyRefs::VisitUnaryOperator(UnaryOperator *UO) {
397 // Increment and decrement are uses despite there being no lvalue-to-rvalue
399 if (UO->isIncrementDecrementOp())
400 classify(UO->getSubExpr(), Use);
403 void ClassifyRefs::VisitCallExpr(CallExpr *CE) {
404 // If a value is passed by const reference to a function, we should not assume
405 // that it is initialized by the call, and we conservatively do not assume
407 for (CallExpr::arg_iterator I = CE->arg_begin(), E = CE->arg_end();
409 if ((*I)->getType().isConstQualified() && (*I)->isGLValue())
410 classify(*I, Ignore);
413 void ClassifyRefs::VisitCastExpr(CastExpr *CE) {
414 if (CE->getCastKind() == CK_LValueToRValue)
415 classify(CE->getSubExpr(), Use);
416 else if (CStyleCastExpr *CSE = dyn_cast<CStyleCastExpr>(CE)) {
417 if (CSE->getType()->isVoidType()) {
418 // Squelch any detected load of an uninitialized value if
419 // we cast it to void.
421 classify(CSE->getSubExpr(), Ignore);
426 //------------------------------------------------------------------------====//
427 // Transfer function for uninitialized values analysis.
428 //====------------------------------------------------------------------------//
431 class TransferFunctions : public StmtVisitor<TransferFunctions> {
432 CFGBlockValues &vals;
434 const CFGBlock *block;
435 AnalysisDeclContext ∾
436 const ClassifyRefs &classification;
437 ObjCNoReturn objCNoRet;
438 UninitVariablesHandler &handler;
441 TransferFunctions(CFGBlockValues &vals, const CFG &cfg,
442 const CFGBlock *block, AnalysisDeclContext &ac,
443 const ClassifyRefs &classification,
444 UninitVariablesHandler &handler)
445 : vals(vals), cfg(cfg), block(block), ac(ac),
446 classification(classification), objCNoRet(ac.getASTContext()),
449 void reportUse(const Expr *ex, const VarDecl *vd);
451 void VisitBinaryOperator(BinaryOperator *bo);
452 void VisitBlockExpr(BlockExpr *be);
453 void VisitCallExpr(CallExpr *ce);
454 void VisitDeclRefExpr(DeclRefExpr *dr);
455 void VisitDeclStmt(DeclStmt *ds);
456 void VisitObjCForCollectionStmt(ObjCForCollectionStmt *FS);
457 void VisitObjCMessageExpr(ObjCMessageExpr *ME);
459 bool isTrackedVar(const VarDecl *vd) {
460 return ::isTrackedVar(vd, cast<DeclContext>(ac.getDecl()));
463 FindVarResult findVar(const Expr *ex) {
464 return ::findVar(ex, cast<DeclContext>(ac.getDecl()));
467 UninitUse getUninitUse(const Expr *ex, const VarDecl *vd, Value v) {
468 UninitUse Use(ex, isAlwaysUninit(v));
470 assert(isUninitialized(v));
471 if (Use.getKind() == UninitUse::Always)
474 // If an edge which leads unconditionally to this use did not initialize
475 // the variable, we can say something stronger than 'may be uninitialized':
476 // we can say 'either it's used uninitialized or you have dead code'.
478 // We track the number of successors of a node which have been visited, and
479 // visit a node once we have visited all of its successors. Only edges where
480 // the variable might still be uninitialized are followed. Since a variable
481 // can't transfer from being initialized to being uninitialized, this will
482 // trace out the subgraph which inevitably leads to the use and does not
483 // initialize the variable. We do not want to skip past loops, since their
484 // non-termination might be correlated with the initialization condition.
488 // void f(bool a, bool b) {
493 // block4: } else if (b) {
494 // block5: while (!a) {
495 // block6: do_work(&a);
504 // Starting from the maybe-uninitialized use in block 9:
505 // * Block 7 is not visited because we have only visited one of its two
507 // * Block 8 is visited because we've visited its only successor.
509 // * Block 7 is visited because we've now visited both of its successors.
511 // * Blocks 1, 2, 4, 5, and 6 are not visited because we didn't visit all
512 // of their successors (we didn't visit 4, 3, 5, 6, and 5, respectively).
513 // * Block 3 is not visited because it initializes 'n'.
514 // Now the algorithm terminates, having visited blocks 7 and 8, and having
515 // found the frontier is blocks 2, 4, and 5.
517 // 'n' is definitely uninitialized for two edges into block 7 (from blocks 2
518 // and 4), so we report that any time either of those edges is taken (in
519 // each case when 'b == false'), 'n' is used uninitialized.
520 SmallVector<const CFGBlock*, 32> Queue;
521 SmallVector<unsigned, 32> SuccsVisited(cfg.getNumBlockIDs(), 0);
522 Queue.push_back(block);
523 // Specify that we've already visited all successors of the starting block.
524 // This has the dual purpose of ensuring we never add it to the queue, and
525 // of marking it as not being a candidate element of the frontier.
526 SuccsVisited[block->getBlockID()] = block->succ_size();
527 while (!Queue.empty()) {
528 const CFGBlock *B = Queue.pop_back_val();
530 // If the use is always reached from the entry block, make a note of that.
531 if (B == &cfg.getEntry())
532 Use.setUninitAfterCall();
534 for (CFGBlock::const_pred_iterator I = B->pred_begin(), E = B->pred_end();
536 const CFGBlock *Pred = *I;
540 Value AtPredExit = vals.getValue(Pred, B, vd);
541 if (AtPredExit == Initialized)
542 // This block initializes the variable.
544 if (AtPredExit == MayUninitialized &&
545 vals.getValue(B, nullptr, vd) == Uninitialized) {
546 // This block declares the variable (uninitialized), and is reachable
547 // from a block that initializes the variable. We can't guarantee to
548 // give an earlier location for the diagnostic (and it appears that
549 // this code is intended to be reachable) so give a diagnostic here
550 // and go no further down this path.
551 Use.setUninitAfterDecl();
555 unsigned &SV = SuccsVisited[Pred->getBlockID()];
557 // When visiting the first successor of a block, mark all NULL
558 // successors as having been visited.
559 for (CFGBlock::const_succ_iterator SI = Pred->succ_begin(),
560 SE = Pred->succ_end();
566 if (++SV == Pred->succ_size())
567 // All paths from this block lead to the use and don't initialize the
569 Queue.push_back(Pred);
573 // Scan the frontier, looking for blocks where the variable was
575 for (CFG::const_iterator BI = cfg.begin(), BE = cfg.end(); BI != BE; ++BI) {
576 const CFGBlock *Block = *BI;
577 unsigned BlockID = Block->getBlockID();
578 const Stmt *Term = Block->getTerminator();
579 if (SuccsVisited[BlockID] && SuccsVisited[BlockID] < Block->succ_size() &&
581 // This block inevitably leads to the use. If we have an edge from here
582 // to a post-dominator block, and the variable is uninitialized on that
583 // edge, we have found a bug.
584 for (CFGBlock::const_succ_iterator I = Block->succ_begin(),
585 E = Block->succ_end(); I != E; ++I) {
586 const CFGBlock *Succ = *I;
587 if (Succ && SuccsVisited[Succ->getBlockID()] >= Succ->succ_size() &&
588 vals.getValue(Block, Succ, vd) == Uninitialized) {
589 // Switch cases are a special case: report the label to the caller
590 // as the 'terminator', not the switch statement itself. Suppress
591 // situations where no label matched: we can't be sure that's
593 if (isa<SwitchStmt>(Term)) {
594 const Stmt *Label = Succ->getLabel();
595 if (!Label || !isa<SwitchCase>(Label))
596 // Might not be possible.
598 UninitUse::Branch Branch;
599 Branch.Terminator = Label;
600 Branch.Output = 0; // Ignored.
601 Use.addUninitBranch(Branch);
603 UninitUse::Branch Branch;
604 Branch.Terminator = Term;
605 Branch.Output = I - Block->succ_begin();
606 Use.addUninitBranch(Branch);
618 void TransferFunctions::reportUse(const Expr *ex, const VarDecl *vd) {
620 if (isUninitialized(v))
621 handler.handleUseOfUninitVariable(vd, getUninitUse(ex, vd, v));
624 void TransferFunctions::VisitObjCForCollectionStmt(ObjCForCollectionStmt *FS) {
625 // This represents an initialization of the 'element' value.
626 if (DeclStmt *DS = dyn_cast<DeclStmt>(FS->getElement())) {
627 const VarDecl *VD = cast<VarDecl>(DS->getSingleDecl());
628 if (isTrackedVar(VD))
629 vals[VD] = Initialized;
633 void TransferFunctions::VisitBlockExpr(BlockExpr *be) {
634 const BlockDecl *bd = be->getBlockDecl();
635 for (const auto &I : bd->captures()) {
636 const VarDecl *vd = I.getVariable();
637 if (!isTrackedVar(vd))
640 vals[vd] = Initialized;
647 void TransferFunctions::VisitCallExpr(CallExpr *ce) {
648 if (Decl *Callee = ce->getCalleeDecl()) {
649 if (Callee->hasAttr<ReturnsTwiceAttr>()) {
650 // After a call to a function like setjmp or vfork, any variable which is
651 // initialized anywhere within this function may now be initialized. For
652 // now, just assume such a call initializes all variables. FIXME: Only
653 // mark variables as initialized if they have an initializer which is
654 // reachable from here.
655 vals.setAllScratchValues(Initialized);
657 else if (Callee->hasAttr<AnalyzerNoReturnAttr>()) {
658 // Functions labeled like "analyzer_noreturn" are often used to denote
659 // "panic" functions that in special debug situations can still return,
660 // but for the most part should not be treated as returning. This is a
661 // useful annotation borrowed from the static analyzer that is useful for
662 // suppressing branch-specific false positives when we call one of these
663 // functions but keep pretending the path continues (when in reality the
664 // user doesn't care).
665 vals.setAllScratchValues(Unknown);
670 void TransferFunctions::VisitDeclRefExpr(DeclRefExpr *dr) {
671 switch (classification.get(dr)) {
672 case ClassifyRefs::Ignore:
674 case ClassifyRefs::Use:
675 reportUse(dr, cast<VarDecl>(dr->getDecl()));
677 case ClassifyRefs::Init:
678 vals[cast<VarDecl>(dr->getDecl())] = Initialized;
680 case ClassifyRefs::SelfInit:
681 handler.handleSelfInit(cast<VarDecl>(dr->getDecl()));
686 void TransferFunctions::VisitBinaryOperator(BinaryOperator *BO) {
687 if (BO->getOpcode() == BO_Assign) {
688 FindVarResult Var = findVar(BO->getLHS());
689 if (const VarDecl *VD = Var.getDecl())
690 vals[VD] = Initialized;
694 void TransferFunctions::VisitDeclStmt(DeclStmt *DS) {
695 for (auto *DI : DS->decls()) {
696 VarDecl *VD = dyn_cast<VarDecl>(DI);
697 if (VD && isTrackedVar(VD)) {
698 if (getSelfInitExpr(VD)) {
699 // If the initializer consists solely of a reference to itself, we
700 // explicitly mark the variable as uninitialized. This allows code
701 // like the following:
705 // to deliberately leave a variable uninitialized. Different analysis
706 // clients can detect this pattern and adjust their reporting
707 // appropriately, but we need to continue to analyze subsequent uses
709 vals[VD] = Uninitialized;
710 } else if (VD->getInit()) {
711 // Treat the new variable as initialized.
712 vals[VD] = Initialized;
714 // No initializer: the variable is now uninitialized. This matters
721 // FIXME: Mark the variable as uninitialized whenever its scope is
722 // left, since its scope could be re-entered by a jump over the
724 vals[VD] = Uninitialized;
730 void TransferFunctions::VisitObjCMessageExpr(ObjCMessageExpr *ME) {
731 // If the Objective-C message expression is an implicit no-return that
732 // is not modeled in the CFG, set the tracked dataflow values to Unknown.
733 if (objCNoRet.isImplicitNoReturn(ME)) {
734 vals.setAllScratchValues(Unknown);
738 //------------------------------------------------------------------------====//
739 // High-level "driver" logic for uninitialized values analysis.
740 //====------------------------------------------------------------------------//
742 static bool runOnBlock(const CFGBlock *block, const CFG &cfg,
743 AnalysisDeclContext &ac, CFGBlockValues &vals,
744 const ClassifyRefs &classification,
745 llvm::BitVector &wasAnalyzed,
746 UninitVariablesHandler &handler) {
747 wasAnalyzed[block->getBlockID()] = true;
749 // Merge in values of predecessor blocks.
751 for (CFGBlock::const_pred_iterator I = block->pred_begin(),
752 E = block->pred_end(); I != E; ++I) {
753 const CFGBlock *pred = *I;
756 if (wasAnalyzed[pred->getBlockID()]) {
757 vals.mergeIntoScratch(vals.getValueVector(pred), isFirst);
761 // Apply the transfer function.
762 TransferFunctions tf(vals, cfg, block, ac, classification, handler);
763 for (CFGBlock::const_iterator I = block->begin(), E = block->end();
765 if (Optional<CFGStmt> cs = I->getAs<CFGStmt>())
766 tf.Visit(const_cast<Stmt*>(cs->getStmt()));
768 return vals.updateValueVectorWithScratch(block);
771 /// PruneBlocksHandler is a special UninitVariablesHandler that is used
772 /// to detect when a CFGBlock has any *potential* use of an uninitialized
773 /// variable. It is mainly used to prune out work during the final
776 struct PruneBlocksHandler : public UninitVariablesHandler {
777 PruneBlocksHandler(unsigned numBlocks)
778 : hadUse(numBlocks, false), hadAnyUse(false),
781 virtual ~PruneBlocksHandler() {}
783 /// Records if a CFGBlock had a potential use of an uninitialized variable.
784 llvm::BitVector hadUse;
786 /// Records if any CFGBlock had a potential use of an uninitialized variable.
789 /// The current block to scribble use information.
790 unsigned currentBlock;
792 void handleUseOfUninitVariable(const VarDecl *vd,
793 const UninitUse &use) override {
794 hadUse[currentBlock] = true;
798 /// Called when the uninitialized variable analysis detects the
799 /// idiom 'int x = x'. All other uses of 'x' within the initializer
800 /// are handled by handleUseOfUninitVariable.
801 void handleSelfInit(const VarDecl *vd) override {
802 hadUse[currentBlock] = true;
808 void clang::runUninitializedVariablesAnalysis(
809 const DeclContext &dc,
811 AnalysisDeclContext &ac,
812 UninitVariablesHandler &handler,
813 UninitVariablesAnalysisStats &stats) {
814 CFGBlockValues vals(cfg);
815 vals.computeSetOfDeclarations(dc);
816 if (vals.hasNoDeclarations())
819 stats.NumVariablesAnalyzed = vals.getNumEntries();
821 // Precompute which expressions are uses and which are initializations.
822 ClassifyRefs classification(ac);
823 cfg.VisitBlockStmts(classification);
825 // Mark all variables uninitialized at the entry.
826 const CFGBlock &entry = cfg.getEntry();
827 ValueVector &vec = vals.getValueVector(&entry);
828 const unsigned n = vals.getNumEntries();
829 for (unsigned j = 0; j < n ; ++j) {
830 vec[j] = Uninitialized;
833 // Proceed with the workist.
834 DataflowWorklist worklist(cfg, *ac.getAnalysis<PostOrderCFGView>());
835 llvm::BitVector previouslyVisited(cfg.getNumBlockIDs());
836 worklist.enqueueSuccessors(&cfg.getEntry());
837 llvm::BitVector wasAnalyzed(cfg.getNumBlockIDs(), false);
838 wasAnalyzed[cfg.getEntry().getBlockID()] = true;
839 PruneBlocksHandler PBH(cfg.getNumBlockIDs());
841 while (const CFGBlock *block = worklist.dequeue()) {
842 PBH.currentBlock = block->getBlockID();
844 // Did the block change?
845 bool changed = runOnBlock(block, cfg, ac, vals,
846 classification, wasAnalyzed, PBH);
847 ++stats.NumBlockVisits;
848 if (changed || !previouslyVisited[block->getBlockID()])
849 worklist.enqueueSuccessors(block);
850 previouslyVisited[block->getBlockID()] = true;
856 // Run through the blocks one more time, and report uninitialized variables.
857 for (CFG::const_iterator BI = cfg.begin(), BE = cfg.end(); BI != BE; ++BI) {
858 const CFGBlock *block = *BI;
859 if (PBH.hadUse[block->getBlockID()]) {
860 runOnBlock(block, cfg, ac, vals, classification, wasAnalyzed, handler);
861 ++stats.NumBlockVisits;
866 UninitVariablesHandler::~UninitVariablesHandler() {}