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1 //== SymbolManager.h - Management of Symbolic Values ------------*- C++ -*--==//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 //  This file defines SymbolManager, a class that manages symbolic values
11 //  created for use by ExprEngine and related classes.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
16 #include "clang/Analysis/Analyses/LiveVariables.h"
17 #include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/Store.h"
19 #include "llvm/Support/raw_ostream.h"
20 
21 using namespace clang;
22 using namespace ento;
23 
anchor()24 void SymExpr::anchor() { }
25 
dump() const26 void SymExpr::dump() const {
27   dumpToStream(llvm::errs());
28 }
29 
dumpToStream(raw_ostream & os) const30 void SymIntExpr::dumpToStream(raw_ostream &os) const {
31   os << '(';
32   getLHS()->dumpToStream(os);
33   os << ") "
34      << BinaryOperator::getOpcodeStr(getOpcode()) << ' '
35      << getRHS().getZExtValue();
36   if (getRHS().isUnsigned())
37     os << 'U';
38 }
39 
dumpToStream(raw_ostream & os) const40 void IntSymExpr::dumpToStream(raw_ostream &os) const {
41   os << getLHS().getZExtValue();
42   if (getLHS().isUnsigned())
43     os << 'U';
44   os << ' '
45      << BinaryOperator::getOpcodeStr(getOpcode())
46      << " (";
47   getRHS()->dumpToStream(os);
48   os << ')';
49 }
50 
dumpToStream(raw_ostream & os) const51 void SymSymExpr::dumpToStream(raw_ostream &os) const {
52   os << '(';
53   getLHS()->dumpToStream(os);
54   os << ") "
55      << BinaryOperator::getOpcodeStr(getOpcode())
56      << " (";
57   getRHS()->dumpToStream(os);
58   os << ')';
59 }
60 
dumpToStream(raw_ostream & os) const61 void SymbolCast::dumpToStream(raw_ostream &os) const {
62   os << '(' << ToTy.getAsString() << ") (";
63   Operand->dumpToStream(os);
64   os << ')';
65 }
66 
dumpToStream(raw_ostream & os) const67 void SymbolConjured::dumpToStream(raw_ostream &os) const {
68   os << "conj_$" << getSymbolID() << '{' << T.getAsString() << '}';
69 }
70 
dumpToStream(raw_ostream & os) const71 void SymbolDerived::dumpToStream(raw_ostream &os) const {
72   os << "derived_$" << getSymbolID() << '{'
73      << getParentSymbol() << ',' << getRegion() << '}';
74 }
75 
dumpToStream(raw_ostream & os) const76 void SymbolExtent::dumpToStream(raw_ostream &os) const {
77   os << "extent_$" << getSymbolID() << '{' << getRegion() << '}';
78 }
79 
dumpToStream(raw_ostream & os) const80 void SymbolMetadata::dumpToStream(raw_ostream &os) const {
81   os << "meta_$" << getSymbolID() << '{'
82      << getRegion() << ',' << T.getAsString() << '}';
83 }
84 
anchor()85 void SymbolData::anchor() { }
86 
dumpToStream(raw_ostream & os) const87 void SymbolRegionValue::dumpToStream(raw_ostream &os) const {
88   os << "reg_$" << getSymbolID() << "<" << R << ">";
89 }
90 
operator ==(const symbol_iterator & X) const91 bool SymExpr::symbol_iterator::operator==(const symbol_iterator &X) const {
92   return itr == X.itr;
93 }
94 
operator !=(const symbol_iterator & X) const95 bool SymExpr::symbol_iterator::operator!=(const symbol_iterator &X) const {
96   return itr != X.itr;
97 }
98 
symbol_iterator(const SymExpr * SE)99 SymExpr::symbol_iterator::symbol_iterator(const SymExpr *SE) {
100   itr.push_back(SE);
101 }
102 
operator ++()103 SymExpr::symbol_iterator &SymExpr::symbol_iterator::operator++() {
104   assert(!itr.empty() && "attempting to iterate on an 'end' iterator");
105   expand();
106   return *this;
107 }
108 
operator *()109 SymbolRef SymExpr::symbol_iterator::operator*() {
110   assert(!itr.empty() && "attempting to dereference an 'end' iterator");
111   return itr.back();
112 }
113 
expand()114 void SymExpr::symbol_iterator::expand() {
115   const SymExpr *SE = itr.back();
116   itr.pop_back();
117 
118   switch (SE->getKind()) {
119     case SymExpr::RegionValueKind:
120     case SymExpr::ConjuredKind:
121     case SymExpr::DerivedKind:
122     case SymExpr::ExtentKind:
123     case SymExpr::MetadataKind:
124       return;
125     case SymExpr::CastSymbolKind:
126       itr.push_back(cast<SymbolCast>(SE)->getOperand());
127       return;
128     case SymExpr::SymIntKind:
129       itr.push_back(cast<SymIntExpr>(SE)->getLHS());
130       return;
131     case SymExpr::IntSymKind:
132       itr.push_back(cast<IntSymExpr>(SE)->getRHS());
133       return;
134     case SymExpr::SymSymKind: {
135       const SymSymExpr *x = cast<SymSymExpr>(SE);
136       itr.push_back(x->getLHS());
137       itr.push_back(x->getRHS());
138       return;
139     }
140   }
141   llvm_unreachable("unhandled expansion case");
142 }
143 
computeComplexity() const144 unsigned SymExpr::computeComplexity() const {
145   unsigned R = 0;
146   for (symbol_iterator I = symbol_begin(), E = symbol_end(); I != E; ++I)
147     R++;
148   return R;
149 }
150 
151 const SymbolRegionValue*
getRegionValueSymbol(const TypedValueRegion * R)152 SymbolManager::getRegionValueSymbol(const TypedValueRegion* R) {
153   llvm::FoldingSetNodeID profile;
154   SymbolRegionValue::Profile(profile, R);
155   void *InsertPos;
156   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
157   if (!SD) {
158     SD = (SymExpr*) BPAlloc.Allocate<SymbolRegionValue>();
159     new (SD) SymbolRegionValue(SymbolCounter, R);
160     DataSet.InsertNode(SD, InsertPos);
161     ++SymbolCounter;
162   }
163 
164   return cast<SymbolRegionValue>(SD);
165 }
166 
conjureSymbol(const Stmt * E,const LocationContext * LCtx,QualType T,unsigned Count,const void * SymbolTag)167 const SymbolConjured* SymbolManager::conjureSymbol(const Stmt *E,
168                                                    const LocationContext *LCtx,
169                                                    QualType T,
170                                                    unsigned Count,
171                                                    const void *SymbolTag) {
172   llvm::FoldingSetNodeID profile;
173   SymbolConjured::Profile(profile, E, T, Count, LCtx, SymbolTag);
174   void *InsertPos;
175   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
176   if (!SD) {
177     SD = (SymExpr*) BPAlloc.Allocate<SymbolConjured>();
178     new (SD) SymbolConjured(SymbolCounter, E, LCtx, T, Count, SymbolTag);
179     DataSet.InsertNode(SD, InsertPos);
180     ++SymbolCounter;
181   }
182 
183   return cast<SymbolConjured>(SD);
184 }
185 
186 const SymbolDerived*
getDerivedSymbol(SymbolRef parentSymbol,const TypedValueRegion * R)187 SymbolManager::getDerivedSymbol(SymbolRef parentSymbol,
188                                 const TypedValueRegion *R) {
189 
190   llvm::FoldingSetNodeID profile;
191   SymbolDerived::Profile(profile, parentSymbol, R);
192   void *InsertPos;
193   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
194   if (!SD) {
195     SD = (SymExpr*) BPAlloc.Allocate<SymbolDerived>();
196     new (SD) SymbolDerived(SymbolCounter, parentSymbol, R);
197     DataSet.InsertNode(SD, InsertPos);
198     ++SymbolCounter;
199   }
200 
201   return cast<SymbolDerived>(SD);
202 }
203 
204 const SymbolExtent*
getExtentSymbol(const SubRegion * R)205 SymbolManager::getExtentSymbol(const SubRegion *R) {
206   llvm::FoldingSetNodeID profile;
207   SymbolExtent::Profile(profile, R);
208   void *InsertPos;
209   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
210   if (!SD) {
211     SD = (SymExpr*) BPAlloc.Allocate<SymbolExtent>();
212     new (SD) SymbolExtent(SymbolCounter, R);
213     DataSet.InsertNode(SD, InsertPos);
214     ++SymbolCounter;
215   }
216 
217   return cast<SymbolExtent>(SD);
218 }
219 
220 const SymbolMetadata*
getMetadataSymbol(const MemRegion * R,const Stmt * S,QualType T,unsigned Count,const void * SymbolTag)221 SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
222                                  unsigned Count, const void *SymbolTag) {
223 
224   llvm::FoldingSetNodeID profile;
225   SymbolMetadata::Profile(profile, R, S, T, Count, SymbolTag);
226   void *InsertPos;
227   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
228   if (!SD) {
229     SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
230     new (SD) SymbolMetadata(SymbolCounter, R, S, T, Count, SymbolTag);
231     DataSet.InsertNode(SD, InsertPos);
232     ++SymbolCounter;
233   }
234 
235   return cast<SymbolMetadata>(SD);
236 }
237 
238 const SymbolCast*
getCastSymbol(const SymExpr * Op,QualType From,QualType To)239 SymbolManager::getCastSymbol(const SymExpr *Op,
240                              QualType From, QualType To) {
241   llvm::FoldingSetNodeID ID;
242   SymbolCast::Profile(ID, Op, From, To);
243   void *InsertPos;
244   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
245   if (!data) {
246     data = (SymbolCast*) BPAlloc.Allocate<SymbolCast>();
247     new (data) SymbolCast(Op, From, To);
248     DataSet.InsertNode(data, InsertPos);
249   }
250 
251   return cast<SymbolCast>(data);
252 }
253 
getSymIntExpr(const SymExpr * lhs,BinaryOperator::Opcode op,const llvm::APSInt & v,QualType t)254 const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
255                                                BinaryOperator::Opcode op,
256                                                const llvm::APSInt& v,
257                                                QualType t) {
258   llvm::FoldingSetNodeID ID;
259   SymIntExpr::Profile(ID, lhs, op, v, t);
260   void *InsertPos;
261   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
262 
263   if (!data) {
264     data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
265     new (data) SymIntExpr(lhs, op, v, t);
266     DataSet.InsertNode(data, InsertPos);
267   }
268 
269   return cast<SymIntExpr>(data);
270 }
271 
getIntSymExpr(const llvm::APSInt & lhs,BinaryOperator::Opcode op,const SymExpr * rhs,QualType t)272 const IntSymExpr *SymbolManager::getIntSymExpr(const llvm::APSInt& lhs,
273                                                BinaryOperator::Opcode op,
274                                                const SymExpr *rhs,
275                                                QualType t) {
276   llvm::FoldingSetNodeID ID;
277   IntSymExpr::Profile(ID, lhs, op, rhs, t);
278   void *InsertPos;
279   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
280 
281   if (!data) {
282     data = (IntSymExpr*) BPAlloc.Allocate<IntSymExpr>();
283     new (data) IntSymExpr(lhs, op, rhs, t);
284     DataSet.InsertNode(data, InsertPos);
285   }
286 
287   return cast<IntSymExpr>(data);
288 }
289 
getSymSymExpr(const SymExpr * lhs,BinaryOperator::Opcode op,const SymExpr * rhs,QualType t)290 const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
291                                                BinaryOperator::Opcode op,
292                                                const SymExpr *rhs,
293                                                QualType t) {
294   llvm::FoldingSetNodeID ID;
295   SymSymExpr::Profile(ID, lhs, op, rhs, t);
296   void *InsertPos;
297   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
298 
299   if (!data) {
300     data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
301     new (data) SymSymExpr(lhs, op, rhs, t);
302     DataSet.InsertNode(data, InsertPos);
303   }
304 
305   return cast<SymSymExpr>(data);
306 }
307 
getType() const308 QualType SymbolConjured::getType() const {
309   return T;
310 }
311 
getType() const312 QualType SymbolDerived::getType() const {
313   return R->getValueType();
314 }
315 
getType() const316 QualType SymbolExtent::getType() const {
317   ASTContext &Ctx = R->getMemRegionManager()->getContext();
318   return Ctx.getSizeType();
319 }
320 
getType() const321 QualType SymbolMetadata::getType() const {
322   return T;
323 }
324 
getType() const325 QualType SymbolRegionValue::getType() const {
326   return R->getValueType();
327 }
328 
~SymbolManager()329 SymbolManager::~SymbolManager() {
330   for (SymbolDependTy::const_iterator I = SymbolDependencies.begin(),
331        E = SymbolDependencies.end(); I != E; ++I) {
332     delete I->second;
333   }
334 
335 }
336 
canSymbolicate(QualType T)337 bool SymbolManager::canSymbolicate(QualType T) {
338   T = T.getCanonicalType();
339 
340   if (Loc::isLocType(T))
341     return true;
342 
343   if (T->isIntegralOrEnumerationType())
344     return true;
345 
346   if (T->isRecordType() && !T->isUnionType())
347     return true;
348 
349   return false;
350 }
351 
addSymbolDependency(const SymbolRef Primary,const SymbolRef Dependent)352 void SymbolManager::addSymbolDependency(const SymbolRef Primary,
353                                         const SymbolRef Dependent) {
354   SymbolDependTy::iterator I = SymbolDependencies.find(Primary);
355   SymbolRefSmallVectorTy *dependencies = 0;
356   if (I == SymbolDependencies.end()) {
357     dependencies = new SymbolRefSmallVectorTy();
358     SymbolDependencies[Primary] = dependencies;
359   } else {
360     dependencies = I->second;
361   }
362   dependencies->push_back(Dependent);
363 }
364 
getDependentSymbols(const SymbolRef Primary)365 const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
366                                                      const SymbolRef Primary) {
367   SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
368   if (I == SymbolDependencies.end())
369     return 0;
370   return I->second;
371 }
372 
markDependentsLive(SymbolRef sym)373 void SymbolReaper::markDependentsLive(SymbolRef sym) {
374   // Do not mark dependents more then once.
375   SymbolMapTy::iterator LI = TheLiving.find(sym);
376   assert(LI != TheLiving.end() && "The primary symbol is not live.");
377   if (LI->second == HaveMarkedDependents)
378     return;
379   LI->second = HaveMarkedDependents;
380 
381   if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
382     for (SymbolRefSmallVectorTy::const_iterator I = Deps->begin(),
383                                                 E = Deps->end(); I != E; ++I) {
384       if (TheLiving.find(*I) != TheLiving.end())
385         continue;
386       markLive(*I);
387     }
388   }
389 }
390 
markLive(SymbolRef sym)391 void SymbolReaper::markLive(SymbolRef sym) {
392   TheLiving[sym] = NotProcessed;
393   TheDead.erase(sym);
394   markDependentsLive(sym);
395 }
396 
markLive(const MemRegion * region)397 void SymbolReaper::markLive(const MemRegion *region) {
398   RegionRoots.insert(region);
399 }
400 
markInUse(SymbolRef sym)401 void SymbolReaper::markInUse(SymbolRef sym) {
402   if (isa<SymbolMetadata>(sym))
403     MetadataInUse.insert(sym);
404 }
405 
maybeDead(SymbolRef sym)406 bool SymbolReaper::maybeDead(SymbolRef sym) {
407   if (isLive(sym))
408     return false;
409 
410   TheDead.insert(sym);
411   return true;
412 }
413 
isLiveRegion(const MemRegion * MR)414 bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
415   if (RegionRoots.count(MR))
416     return true;
417 
418   MR = MR->getBaseRegion();
419 
420   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(MR))
421     return isLive(SR->getSymbol());
422 
423   if (const VarRegion *VR = dyn_cast<VarRegion>(MR))
424     return isLive(VR, true);
425 
426   // FIXME: This is a gross over-approximation. What we really need is a way to
427   // tell if anything still refers to this region. Unlike SymbolicRegions,
428   // AllocaRegions don't have associated symbols, though, so we don't actually
429   // have a way to track their liveness.
430   if (isa<AllocaRegion>(MR))
431     return true;
432 
433   if (isa<CXXThisRegion>(MR))
434     return true;
435 
436   if (isa<MemSpaceRegion>(MR))
437     return true;
438 
439   return false;
440 }
441 
isLive(SymbolRef sym)442 bool SymbolReaper::isLive(SymbolRef sym) {
443   if (TheLiving.count(sym)) {
444     markDependentsLive(sym);
445     return true;
446   }
447 
448   bool KnownLive;
449 
450   switch (sym->getKind()) {
451   case SymExpr::RegionValueKind:
452     KnownLive = isLiveRegion(cast<SymbolRegionValue>(sym)->getRegion());
453     break;
454   case SymExpr::ConjuredKind:
455     KnownLive = false;
456     break;
457   case SymExpr::DerivedKind:
458     KnownLive = isLive(cast<SymbolDerived>(sym)->getParentSymbol());
459     break;
460   case SymExpr::ExtentKind:
461     KnownLive = isLiveRegion(cast<SymbolExtent>(sym)->getRegion());
462     break;
463   case SymExpr::MetadataKind:
464     KnownLive = MetadataInUse.count(sym) &&
465                 isLiveRegion(cast<SymbolMetadata>(sym)->getRegion());
466     if (KnownLive)
467       MetadataInUse.erase(sym);
468     break;
469   case SymExpr::SymIntKind:
470     KnownLive = isLive(cast<SymIntExpr>(sym)->getLHS());
471     break;
472   case SymExpr::IntSymKind:
473     KnownLive = isLive(cast<IntSymExpr>(sym)->getRHS());
474     break;
475   case SymExpr::SymSymKind:
476     KnownLive = isLive(cast<SymSymExpr>(sym)->getLHS()) &&
477                 isLive(cast<SymSymExpr>(sym)->getRHS());
478     break;
479   case SymExpr::CastSymbolKind:
480     KnownLive = isLive(cast<SymbolCast>(sym)->getOperand());
481     break;
482   }
483 
484   if (KnownLive)
485     markLive(sym);
486 
487   return KnownLive;
488 }
489 
490 bool
isLive(const Stmt * ExprVal,const LocationContext * ELCtx) const491 SymbolReaper::isLive(const Stmt *ExprVal, const LocationContext *ELCtx) const {
492   if (LCtx == 0)
493     return false;
494 
495   if (LCtx != ELCtx) {
496     // If the reaper's location context is a parent of the expression's
497     // location context, then the expression value is now "out of scope".
498     if (LCtx->isParentOf(ELCtx))
499       return false;
500     return true;
501   }
502 
503   // If no statement is provided, everything is this and parent contexts is live.
504   if (!Loc)
505     return true;
506 
507   return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
508 }
509 
isLive(const VarRegion * VR,bool includeStoreBindings) const510 bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
511   const StackFrameContext *VarContext = VR->getStackFrame();
512 
513   if (!VarContext)
514     return true;
515 
516   if (!LCtx)
517     return false;
518   const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();
519 
520   if (VarContext == CurrentContext) {
521     // If no statement is provided, everything is live.
522     if (!Loc)
523       return true;
524 
525     if (LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, VR->getDecl()))
526       return true;
527 
528     if (!includeStoreBindings)
529       return false;
530 
531     unsigned &cachedQuery =
532       const_cast<SymbolReaper*>(this)->includedRegionCache[VR];
533 
534     if (cachedQuery) {
535       return cachedQuery == 1;
536     }
537 
538     // Query the store to see if the region occurs in any live bindings.
539     if (Store store = reapedStore.getStore()) {
540       bool hasRegion =
541         reapedStore.getStoreManager().includedInBindings(store, VR);
542       cachedQuery = hasRegion ? 1 : 2;
543       return hasRegion;
544     }
545 
546     return false;
547   }
548 
549   return VarContext->isParentOf(CurrentContext);
550 }
551 
~SymbolVisitor()552 SymbolVisitor::~SymbolVisitor() {}
553