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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 
     24 void SymExpr::anchor() { }
     25 
     26 LLVM_DUMP_METHOD void SymExpr::dump() const {
     27   dumpToStream(llvm::errs());
     28 }
     29 
     30 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 
     40 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 
     51 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 
     61 void SymbolCast::dumpToStream(raw_ostream &os) const {
     62   os << '(' << ToTy.getAsString() << ") (";
     63   Operand->dumpToStream(os);
     64   os << ')';
     65 }
     66 
     67 void SymbolConjured::dumpToStream(raw_ostream &os) const {
     68   os << "conj_$" << getSymbolID() << '{' << T.getAsString() << '}';
     69 }
     70 
     71 void SymbolDerived::dumpToStream(raw_ostream &os) const {
     72   os << "derived_$" << getSymbolID() << '{'
     73      << getParentSymbol() << ',' << getRegion() << '}';
     74 }
     75 
     76 void SymbolExtent::dumpToStream(raw_ostream &os) const {
     77   os << "extent_$" << getSymbolID() << '{' << getRegion() << '}';
     78 }
     79 
     80 void SymbolMetadata::dumpToStream(raw_ostream &os) const {
     81   os << "meta_$" << getSymbolID() << '{'
     82      << getRegion() << ',' << T.getAsString() << '}';
     83 }
     84 
     85 void SymbolData::anchor() { }
     86 
     87 void SymbolRegionValue::dumpToStream(raw_ostream &os) const {
     88   os << "reg_$" << getSymbolID() << "<" << R << ">";
     89 }
     90 
     91 bool SymExpr::symbol_iterator::operator==(const symbol_iterator &X) const {
     92   return itr == X.itr;
     93 }
     94 
     95 bool SymExpr::symbol_iterator::operator!=(const symbol_iterator &X) const {
     96   return itr != X.itr;
     97 }
     98 
     99 SymExpr::symbol_iterator::symbol_iterator(const SymExpr *SE) {
    100   itr.push_back(SE);
    101 }
    102 
    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 
    109 SymbolRef SymExpr::symbol_iterator::operator*() {
    110   assert(!itr.empty() && "attempting to dereference an 'end' iterator");
    111   return itr.back();
    112 }
    113 
    114 void SymExpr::symbol_iterator::expand() {
    115   const SymExpr *SE = itr.pop_back_val();
    116 
    117   switch (SE->getKind()) {
    118     case SymExpr::SymbolRegionValueKind:
    119     case SymExpr::SymbolConjuredKind:
    120     case SymExpr::SymbolDerivedKind:
    121     case SymExpr::SymbolExtentKind:
    122     case SymExpr::SymbolMetadataKind:
    123       return;
    124     case SymExpr::SymbolCastKind:
    125       itr.push_back(cast<SymbolCast>(SE)->getOperand());
    126       return;
    127     case SymExpr::SymIntExprKind:
    128       itr.push_back(cast<SymIntExpr>(SE)->getLHS());
    129       return;
    130     case SymExpr::IntSymExprKind:
    131       itr.push_back(cast<IntSymExpr>(SE)->getRHS());
    132       return;
    133     case SymExpr::SymSymExprKind: {
    134       const SymSymExpr *x = cast<SymSymExpr>(SE);
    135       itr.push_back(x->getLHS());
    136       itr.push_back(x->getRHS());
    137       return;
    138     }
    139   }
    140   llvm_unreachable("unhandled expansion case");
    141 }
    142 
    143 unsigned SymExpr::computeComplexity() const {
    144   unsigned R = 0;
    145   for (symbol_iterator I = symbol_begin(), E = symbol_end(); I != E; ++I)
    146     R++;
    147   return R;
    148 }
    149 
    150 const SymbolRegionValue*
    151 SymbolManager::getRegionValueSymbol(const TypedValueRegion* R) {
    152   llvm::FoldingSetNodeID profile;
    153   SymbolRegionValue::Profile(profile, R);
    154   void *InsertPos;
    155   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    156   if (!SD) {
    157     SD = (SymExpr*) BPAlloc.Allocate<SymbolRegionValue>();
    158     new (SD) SymbolRegionValue(SymbolCounter, R);
    159     DataSet.InsertNode(SD, InsertPos);
    160     ++SymbolCounter;
    161   }
    162 
    163   return cast<SymbolRegionValue>(SD);
    164 }
    165 
    166 const SymbolConjured* SymbolManager::conjureSymbol(const Stmt *E,
    167                                                    const LocationContext *LCtx,
    168                                                    QualType T,
    169                                                    unsigned Count,
    170                                                    const void *SymbolTag) {
    171   llvm::FoldingSetNodeID profile;
    172   SymbolConjured::Profile(profile, E, T, Count, LCtx, SymbolTag);
    173   void *InsertPos;
    174   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    175   if (!SD) {
    176     SD = (SymExpr*) BPAlloc.Allocate<SymbolConjured>();
    177     new (SD) SymbolConjured(SymbolCounter, E, LCtx, T, Count, SymbolTag);
    178     DataSet.InsertNode(SD, InsertPos);
    179     ++SymbolCounter;
    180   }
    181 
    182   return cast<SymbolConjured>(SD);
    183 }
    184 
    185 const SymbolDerived*
    186 SymbolManager::getDerivedSymbol(SymbolRef parentSymbol,
    187                                 const TypedValueRegion *R) {
    188 
    189   llvm::FoldingSetNodeID profile;
    190   SymbolDerived::Profile(profile, parentSymbol, R);
    191   void *InsertPos;
    192   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    193   if (!SD) {
    194     SD = (SymExpr*) BPAlloc.Allocate<SymbolDerived>();
    195     new (SD) SymbolDerived(SymbolCounter, parentSymbol, R);
    196     DataSet.InsertNode(SD, InsertPos);
    197     ++SymbolCounter;
    198   }
    199 
    200   return cast<SymbolDerived>(SD);
    201 }
    202 
    203 const SymbolExtent*
    204 SymbolManager::getExtentSymbol(const SubRegion *R) {
    205   llvm::FoldingSetNodeID profile;
    206   SymbolExtent::Profile(profile, R);
    207   void *InsertPos;
    208   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    209   if (!SD) {
    210     SD = (SymExpr*) BPAlloc.Allocate<SymbolExtent>();
    211     new (SD) SymbolExtent(SymbolCounter, R);
    212     DataSet.InsertNode(SD, InsertPos);
    213     ++SymbolCounter;
    214   }
    215 
    216   return cast<SymbolExtent>(SD);
    217 }
    218 
    219 const SymbolMetadata*
    220 SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
    221                                  unsigned Count, const void *SymbolTag) {
    222 
    223   llvm::FoldingSetNodeID profile;
    224   SymbolMetadata::Profile(profile, R, S, T, Count, SymbolTag);
    225   void *InsertPos;
    226   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    227   if (!SD) {
    228     SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
    229     new (SD) SymbolMetadata(SymbolCounter, R, S, T, Count, SymbolTag);
    230     DataSet.InsertNode(SD, InsertPos);
    231     ++SymbolCounter;
    232   }
    233 
    234   return cast<SymbolMetadata>(SD);
    235 }
    236 
    237 const SymbolCast*
    238 SymbolManager::getCastSymbol(const SymExpr *Op,
    239                              QualType From, QualType To) {
    240   llvm::FoldingSetNodeID ID;
    241   SymbolCast::Profile(ID, Op, From, To);
    242   void *InsertPos;
    243   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
    244   if (!data) {
    245     data = (SymbolCast*) BPAlloc.Allocate<SymbolCast>();
    246     new (data) SymbolCast(Op, From, To);
    247     DataSet.InsertNode(data, InsertPos);
    248   }
    249 
    250   return cast<SymbolCast>(data);
    251 }
    252 
    253 const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
    254                                                BinaryOperator::Opcode op,
    255                                                const llvm::APSInt& v,
    256                                                QualType t) {
    257   llvm::FoldingSetNodeID ID;
    258   SymIntExpr::Profile(ID, lhs, op, v, t);
    259   void *InsertPos;
    260   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
    261 
    262   if (!data) {
    263     data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
    264     new (data) SymIntExpr(lhs, op, v, t);
    265     DataSet.InsertNode(data, InsertPos);
    266   }
    267 
    268   return cast<SymIntExpr>(data);
    269 }
    270 
    271 const IntSymExpr *SymbolManager::getIntSymExpr(const llvm::APSInt& lhs,
    272                                                BinaryOperator::Opcode op,
    273                                                const SymExpr *rhs,
    274                                                QualType t) {
    275   llvm::FoldingSetNodeID ID;
    276   IntSymExpr::Profile(ID, lhs, op, rhs, t);
    277   void *InsertPos;
    278   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
    279 
    280   if (!data) {
    281     data = (IntSymExpr*) BPAlloc.Allocate<IntSymExpr>();
    282     new (data) IntSymExpr(lhs, op, rhs, t);
    283     DataSet.InsertNode(data, InsertPos);
    284   }
    285 
    286   return cast<IntSymExpr>(data);
    287 }
    288 
    289 const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
    290                                                BinaryOperator::Opcode op,
    291                                                const SymExpr *rhs,
    292                                                QualType t) {
    293   llvm::FoldingSetNodeID ID;
    294   SymSymExpr::Profile(ID, lhs, op, rhs, t);
    295   void *InsertPos;
    296   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
    297 
    298   if (!data) {
    299     data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
    300     new (data) SymSymExpr(lhs, op, rhs, t);
    301     DataSet.InsertNode(data, InsertPos);
    302   }
    303 
    304   return cast<SymSymExpr>(data);
    305 }
    306 
    307 QualType SymbolConjured::getType() const {
    308   return T;
    309 }
    310 
    311 QualType SymbolDerived::getType() const {
    312   return R->getValueType();
    313 }
    314 
    315 QualType SymbolExtent::getType() const {
    316   ASTContext &Ctx = R->getMemRegionManager()->getContext();
    317   return Ctx.getSizeType();
    318 }
    319 
    320 QualType SymbolMetadata::getType() const {
    321   return T;
    322 }
    323 
    324 QualType SymbolRegionValue::getType() const {
    325   return R->getValueType();
    326 }
    327 
    328 SymbolManager::~SymbolManager() {
    329   llvm::DeleteContainerSeconds(SymbolDependencies);
    330 }
    331 
    332 bool SymbolManager::canSymbolicate(QualType T) {
    333   T = T.getCanonicalType();
    334 
    335   if (Loc::isLocType(T))
    336     return true;
    337 
    338   if (T->isIntegralOrEnumerationType())
    339     return true;
    340 
    341   if (T->isRecordType() && !T->isUnionType())
    342     return true;
    343 
    344   return false;
    345 }
    346 
    347 void SymbolManager::addSymbolDependency(const SymbolRef Primary,
    348                                         const SymbolRef Dependent) {
    349   SymbolDependTy::iterator I = SymbolDependencies.find(Primary);
    350   SymbolRefSmallVectorTy *dependencies = nullptr;
    351   if (I == SymbolDependencies.end()) {
    352     dependencies = new SymbolRefSmallVectorTy();
    353     SymbolDependencies[Primary] = dependencies;
    354   } else {
    355     dependencies = I->second;
    356   }
    357   dependencies->push_back(Dependent);
    358 }
    359 
    360 const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
    361                                                      const SymbolRef Primary) {
    362   SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
    363   if (I == SymbolDependencies.end())
    364     return nullptr;
    365   return I->second;
    366 }
    367 
    368 void SymbolReaper::markDependentsLive(SymbolRef sym) {
    369   // Do not mark dependents more then once.
    370   SymbolMapTy::iterator LI = TheLiving.find(sym);
    371   assert(LI != TheLiving.end() && "The primary symbol is not live.");
    372   if (LI->second == HaveMarkedDependents)
    373     return;
    374   LI->second = HaveMarkedDependents;
    375 
    376   if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
    377     for (SymbolRefSmallVectorTy::const_iterator I = Deps->begin(),
    378                                                 E = Deps->end(); I != E; ++I) {
    379       if (TheLiving.find(*I) != TheLiving.end())
    380         continue;
    381       markLive(*I);
    382     }
    383   }
    384 }
    385 
    386 void SymbolReaper::markLive(SymbolRef sym) {
    387   TheLiving[sym] = NotProcessed;
    388   TheDead.erase(sym);
    389   markDependentsLive(sym);
    390 }
    391 
    392 void SymbolReaper::markLive(const MemRegion *region) {
    393   RegionRoots.insert(region);
    394   markElementIndicesLive(region);
    395 }
    396 
    397 void SymbolReaper::markElementIndicesLive(const MemRegion *region) {
    398   for (auto SR = dyn_cast<SubRegion>(region); SR;
    399        SR = dyn_cast<SubRegion>(SR->getSuperRegion())) {
    400     if (auto ER = dyn_cast<ElementRegion>(SR)) {
    401       SVal Idx = ER->getIndex();
    402       for (auto SI = Idx.symbol_begin(), SE = Idx.symbol_end(); SI != SE; ++SI)
    403         markLive(*SI);
    404     }
    405   }
    406 }
    407 
    408 void SymbolReaper::markInUse(SymbolRef sym) {
    409   if (isa<SymbolMetadata>(sym))
    410     MetadataInUse.insert(sym);
    411 }
    412 
    413 bool SymbolReaper::maybeDead(SymbolRef sym) {
    414   if (isLive(sym))
    415     return false;
    416 
    417   TheDead.insert(sym);
    418   return true;
    419 }
    420 
    421 bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
    422   if (RegionRoots.count(MR))
    423     return true;
    424 
    425   MR = MR->getBaseRegion();
    426 
    427   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(MR))
    428     return isLive(SR->getSymbol());
    429 
    430   if (const VarRegion *VR = dyn_cast<VarRegion>(MR))
    431     return isLive(VR, true);
    432 
    433   // FIXME: This is a gross over-approximation. What we really need is a way to
    434   // tell if anything still refers to this region. Unlike SymbolicRegions,
    435   // AllocaRegions don't have associated symbols, though, so we don't actually
    436   // have a way to track their liveness.
    437   if (isa<AllocaRegion>(MR))
    438     return true;
    439 
    440   if (isa<CXXThisRegion>(MR))
    441     return true;
    442 
    443   if (isa<MemSpaceRegion>(MR))
    444     return true;
    445 
    446   if (isa<CodeTextRegion>(MR))
    447     return true;
    448 
    449   return false;
    450 }
    451 
    452 bool SymbolReaper::isLive(SymbolRef sym) {
    453   if (TheLiving.count(sym)) {
    454     markDependentsLive(sym);
    455     return true;
    456   }
    457 
    458   bool KnownLive;
    459 
    460   switch (sym->getKind()) {
    461   case SymExpr::SymbolRegionValueKind:
    462     KnownLive = isLiveRegion(cast<SymbolRegionValue>(sym)->getRegion());
    463     break;
    464   case SymExpr::SymbolConjuredKind:
    465     KnownLive = false;
    466     break;
    467   case SymExpr::SymbolDerivedKind:
    468     KnownLive = isLive(cast<SymbolDerived>(sym)->getParentSymbol());
    469     break;
    470   case SymExpr::SymbolExtentKind:
    471     KnownLive = isLiveRegion(cast<SymbolExtent>(sym)->getRegion());
    472     break;
    473   case SymExpr::SymbolMetadataKind:
    474     KnownLive = MetadataInUse.count(sym) &&
    475                 isLiveRegion(cast<SymbolMetadata>(sym)->getRegion());
    476     if (KnownLive)
    477       MetadataInUse.erase(sym);
    478     break;
    479   case SymExpr::SymIntExprKind:
    480     KnownLive = isLive(cast<SymIntExpr>(sym)->getLHS());
    481     break;
    482   case SymExpr::IntSymExprKind:
    483     KnownLive = isLive(cast<IntSymExpr>(sym)->getRHS());
    484     break;
    485   case SymExpr::SymSymExprKind:
    486     KnownLive = isLive(cast<SymSymExpr>(sym)->getLHS()) &&
    487                 isLive(cast<SymSymExpr>(sym)->getRHS());
    488     break;
    489   case SymExpr::SymbolCastKind:
    490     KnownLive = isLive(cast<SymbolCast>(sym)->getOperand());
    491     break;
    492   }
    493 
    494   if (KnownLive)
    495     markLive(sym);
    496 
    497   return KnownLive;
    498 }
    499 
    500 bool
    501 SymbolReaper::isLive(const Stmt *ExprVal, const LocationContext *ELCtx) const {
    502   if (LCtx == nullptr)
    503     return false;
    504 
    505   if (LCtx != ELCtx) {
    506     // If the reaper's location context is a parent of the expression's
    507     // location context, then the expression value is now "out of scope".
    508     if (LCtx->isParentOf(ELCtx))
    509       return false;
    510     return true;
    511   }
    512 
    513   // If no statement is provided, everything is this and parent contexts is live.
    514   if (!Loc)
    515     return true;
    516 
    517   return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
    518 }
    519 
    520 bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
    521   const StackFrameContext *VarContext = VR->getStackFrame();
    522 
    523   if (!VarContext)
    524     return true;
    525 
    526   if (!LCtx)
    527     return false;
    528   const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();
    529 
    530   if (VarContext == CurrentContext) {
    531     // If no statement is provided, everything is live.
    532     if (!Loc)
    533       return true;
    534 
    535     if (LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, VR->getDecl()))
    536       return true;
    537 
    538     if (!includeStoreBindings)
    539       return false;
    540 
    541     unsigned &cachedQuery =
    542       const_cast<SymbolReaper*>(this)->includedRegionCache[VR];
    543 
    544     if (cachedQuery) {
    545       return cachedQuery == 1;
    546     }
    547 
    548     // Query the store to see if the region occurs in any live bindings.
    549     if (Store store = reapedStore.getStore()) {
    550       bool hasRegion =
    551         reapedStore.getStoreManager().includedInBindings(store, VR);
    552       cachedQuery = hasRegion ? 1 : 2;
    553       return hasRegion;
    554     }
    555 
    556     return false;
    557   }
    558 
    559   return VarContext->isParentOf(CurrentContext);
    560 }
    561