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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::dump() const {
     25   dumpToStream(llvm::errs());
     26 }
     27 
     28 static void print(raw_ostream &os, BinaryOperator::Opcode Op) {
     29   switch (Op) {
     30     default:
     31       llvm_unreachable("operator printing not implemented");
     32     case BO_Mul: os << '*'  ; break;
     33     case BO_Div: os << '/'  ; break;
     34     case BO_Rem: os << '%'  ; break;
     35     case BO_Add: os << '+'  ; break;
     36     case BO_Sub: os << '-'  ; break;
     37     case BO_Shl: os << "<<" ; break;
     38     case BO_Shr: os << ">>" ; break;
     39     case BO_LT:  os << "<"  ; break;
     40     case BO_GT:  os << '>'  ; break;
     41     case BO_LE:  os << "<=" ; break;
     42     case BO_GE:  os << ">=" ; break;
     43     case BO_EQ:  os << "==" ; break;
     44     case BO_NE:  os << "!=" ; break;
     45     case BO_And: os << '&'  ; break;
     46     case BO_Xor: os << '^'  ; break;
     47     case BO_Or:  os << '|'  ; break;
     48   }
     49 }
     50 
     51 void SymIntExpr::dumpToStream(raw_ostream &os) const {
     52   os << '(';
     53   getLHS()->dumpToStream(os);
     54   os << ") ";
     55   print(os, getOpcode());
     56   os << ' ' << getRHS().getZExtValue();
     57   if (getRHS().isUnsigned()) os << 'U';
     58 }
     59 
     60 void SymSymExpr::dumpToStream(raw_ostream &os) const {
     61   os << '(';
     62   getLHS()->dumpToStream(os);
     63   os << ") ";
     64   os << '(';
     65   getRHS()->dumpToStream(os);
     66   os << ')';
     67 }
     68 
     69 void SymbolConjured::dumpToStream(raw_ostream &os) const {
     70   os << "conj_$" << getSymbolID() << '{' << T.getAsString() << '}';
     71 }
     72 
     73 void SymbolDerived::dumpToStream(raw_ostream &os) const {
     74   os << "derived_$" << getSymbolID() << '{'
     75      << getParentSymbol() << ',' << getRegion() << '}';
     76 }
     77 
     78 void SymbolExtent::dumpToStream(raw_ostream &os) const {
     79   os << "extent_$" << getSymbolID() << '{' << getRegion() << '}';
     80 }
     81 
     82 void SymbolMetadata::dumpToStream(raw_ostream &os) const {
     83   os << "meta_$" << getSymbolID() << '{'
     84      << getRegion() << ',' << T.getAsString() << '}';
     85 }
     86 
     87 void SymbolRegionValue::dumpToStream(raw_ostream &os) const {
     88   os << "reg_$" << getSymbolID() << "<" << R << ">";
     89 }
     90 
     91 const SymbolRegionValue*
     92 SymbolManager::getRegionValueSymbol(const TypedValueRegion* R) {
     93   llvm::FoldingSetNodeID profile;
     94   SymbolRegionValue::Profile(profile, R);
     95   void *InsertPos;
     96   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
     97   if (!SD) {
     98     SD = (SymExpr*) BPAlloc.Allocate<SymbolRegionValue>();
     99     new (SD) SymbolRegionValue(SymbolCounter, R);
    100     DataSet.InsertNode(SD, InsertPos);
    101     ++SymbolCounter;
    102   }
    103 
    104   return cast<SymbolRegionValue>(SD);
    105 }
    106 
    107 const SymbolConjured*
    108 SymbolManager::getConjuredSymbol(const Stmt *E, QualType T, unsigned Count,
    109                                  const void *SymbolTag) {
    110 
    111   llvm::FoldingSetNodeID profile;
    112   SymbolConjured::Profile(profile, E, T, Count, SymbolTag);
    113   void *InsertPos;
    114   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    115   if (!SD) {
    116     SD = (SymExpr*) BPAlloc.Allocate<SymbolConjured>();
    117     new (SD) SymbolConjured(SymbolCounter, E, T, Count, SymbolTag);
    118     DataSet.InsertNode(SD, InsertPos);
    119     ++SymbolCounter;
    120   }
    121 
    122   return cast<SymbolConjured>(SD);
    123 }
    124 
    125 const SymbolDerived*
    126 SymbolManager::getDerivedSymbol(SymbolRef parentSymbol,
    127                                 const TypedValueRegion *R) {
    128 
    129   llvm::FoldingSetNodeID profile;
    130   SymbolDerived::Profile(profile, parentSymbol, R);
    131   void *InsertPos;
    132   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    133   if (!SD) {
    134     SD = (SymExpr*) BPAlloc.Allocate<SymbolDerived>();
    135     new (SD) SymbolDerived(SymbolCounter, parentSymbol, R);
    136     DataSet.InsertNode(SD, InsertPos);
    137     ++SymbolCounter;
    138   }
    139 
    140   return cast<SymbolDerived>(SD);
    141 }
    142 
    143 const SymbolExtent*
    144 SymbolManager::getExtentSymbol(const SubRegion *R) {
    145   llvm::FoldingSetNodeID profile;
    146   SymbolExtent::Profile(profile, R);
    147   void *InsertPos;
    148   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    149   if (!SD) {
    150     SD = (SymExpr*) BPAlloc.Allocate<SymbolExtent>();
    151     new (SD) SymbolExtent(SymbolCounter, R);
    152     DataSet.InsertNode(SD, InsertPos);
    153     ++SymbolCounter;
    154   }
    155 
    156   return cast<SymbolExtent>(SD);
    157 }
    158 
    159 const SymbolMetadata*
    160 SymbolManager::getMetadataSymbol(const MemRegion* R, const Stmt *S, QualType T,
    161                                  unsigned Count, const void *SymbolTag) {
    162 
    163   llvm::FoldingSetNodeID profile;
    164   SymbolMetadata::Profile(profile, R, S, T, Count, SymbolTag);
    165   void *InsertPos;
    166   SymExpr *SD = DataSet.FindNodeOrInsertPos(profile, InsertPos);
    167   if (!SD) {
    168     SD = (SymExpr*) BPAlloc.Allocate<SymbolMetadata>();
    169     new (SD) SymbolMetadata(SymbolCounter, R, S, T, Count, SymbolTag);
    170     DataSet.InsertNode(SD, InsertPos);
    171     ++SymbolCounter;
    172   }
    173 
    174   return cast<SymbolMetadata>(SD);
    175 }
    176 
    177 const SymIntExpr *SymbolManager::getSymIntExpr(const SymExpr *lhs,
    178                                                BinaryOperator::Opcode op,
    179                                                const llvm::APSInt& v,
    180                                                QualType t) {
    181   llvm::FoldingSetNodeID ID;
    182   SymIntExpr::Profile(ID, lhs, op, v, t);
    183   void *InsertPos;
    184   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
    185 
    186   if (!data) {
    187     data = (SymIntExpr*) BPAlloc.Allocate<SymIntExpr>();
    188     new (data) SymIntExpr(lhs, op, v, t);
    189     DataSet.InsertNode(data, InsertPos);
    190   }
    191 
    192   return cast<SymIntExpr>(data);
    193 }
    194 
    195 const SymSymExpr *SymbolManager::getSymSymExpr(const SymExpr *lhs,
    196                                                BinaryOperator::Opcode op,
    197                                                const SymExpr *rhs,
    198                                                QualType t) {
    199   llvm::FoldingSetNodeID ID;
    200   SymSymExpr::Profile(ID, lhs, op, rhs, t);
    201   void *InsertPos;
    202   SymExpr *data = DataSet.FindNodeOrInsertPos(ID, InsertPos);
    203 
    204   if (!data) {
    205     data = (SymSymExpr*) BPAlloc.Allocate<SymSymExpr>();
    206     new (data) SymSymExpr(lhs, op, rhs, t);
    207     DataSet.InsertNode(data, InsertPos);
    208   }
    209 
    210   return cast<SymSymExpr>(data);
    211 }
    212 
    213 QualType SymbolConjured::getType(ASTContext&) const {
    214   return T;
    215 }
    216 
    217 QualType SymbolDerived::getType(ASTContext &Ctx) const {
    218   return R->getValueType();
    219 }
    220 
    221 QualType SymbolExtent::getType(ASTContext &Ctx) const {
    222   return Ctx.getSizeType();
    223 }
    224 
    225 QualType SymbolMetadata::getType(ASTContext&) const {
    226   return T;
    227 }
    228 
    229 QualType SymbolRegionValue::getType(ASTContext &C) const {
    230   return R->getValueType();
    231 }
    232 
    233 SymbolManager::~SymbolManager() {
    234   for (SymbolDependTy::const_iterator I = SymbolDependencies.begin(),
    235        E = SymbolDependencies.end(); I != E; ++I) {
    236     delete I->second;
    237   }
    238 
    239 }
    240 
    241 bool SymbolManager::canSymbolicate(QualType T) {
    242   T = T.getCanonicalType();
    243 
    244   if (Loc::isLocType(T))
    245     return true;
    246 
    247   if (T->isIntegerType())
    248     return T->isScalarType();
    249 
    250   if (T->isRecordType() && !T->isUnionType())
    251     return true;
    252 
    253   return false;
    254 }
    255 
    256 void SymbolManager::addSymbolDependency(const SymbolRef Primary,
    257                                         const SymbolRef Dependent) {
    258   SymbolDependTy::iterator I = SymbolDependencies.find(Primary);
    259   SymbolRefSmallVectorTy *dependencies = 0;
    260   if (I == SymbolDependencies.end()) {
    261     dependencies = new SymbolRefSmallVectorTy();
    262     SymbolDependencies[Primary] = dependencies;
    263   } else {
    264     dependencies = I->second;
    265   }
    266   dependencies->push_back(Dependent);
    267 }
    268 
    269 const SymbolRefSmallVectorTy *SymbolManager::getDependentSymbols(
    270                                                      const SymbolRef Primary) {
    271   SymbolDependTy::const_iterator I = SymbolDependencies.find(Primary);
    272   if (I == SymbolDependencies.end())
    273     return 0;
    274   return I->second;
    275 }
    276 
    277 void SymbolReaper::markDependentsLive(SymbolRef sym) {
    278   // Do not mark dependents more then once.
    279   SymbolMapTy::iterator LI = TheLiving.find(sym);
    280   assert(LI != TheLiving.end() && "The primary symbol is not live.");
    281   if (LI->second == HaveMarkedDependents)
    282     return;
    283   LI->second = HaveMarkedDependents;
    284 
    285   if (const SymbolRefSmallVectorTy *Deps = SymMgr.getDependentSymbols(sym)) {
    286     for (SymbolRefSmallVectorTy::const_iterator I = Deps->begin(),
    287                                                 E = Deps->end(); I != E; ++I) {
    288       if (TheLiving.find(*I) != TheLiving.end())
    289         continue;
    290       markLive(*I);
    291     }
    292   }
    293 }
    294 
    295 void SymbolReaper::markLive(SymbolRef sym) {
    296   TheLiving[sym] = NotProcessed;
    297   TheDead.erase(sym);
    298   markDependentsLive(sym);
    299 }
    300 
    301 void SymbolReaper::markLive(const MemRegion *region) {
    302   RegionRoots.insert(region);
    303 }
    304 
    305 void SymbolReaper::markInUse(SymbolRef sym) {
    306   if (isa<SymbolMetadata>(sym))
    307     MetadataInUse.insert(sym);
    308 }
    309 
    310 bool SymbolReaper::maybeDead(SymbolRef sym) {
    311   if (isLive(sym))
    312     return false;
    313 
    314   TheDead.insert(sym);
    315   return true;
    316 }
    317 
    318 bool SymbolReaper::isLiveRegion(const MemRegion *MR) {
    319   if (RegionRoots.count(MR))
    320     return true;
    321 
    322   MR = MR->getBaseRegion();
    323 
    324   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(MR))
    325     return isLive(SR->getSymbol());
    326 
    327   if (const VarRegion *VR = dyn_cast<VarRegion>(MR))
    328     return isLive(VR, true);
    329 
    330   // FIXME: This is a gross over-approximation. What we really need is a way to
    331   // tell if anything still refers to this region. Unlike SymbolicRegions,
    332   // AllocaRegions don't have associated symbols, though, so we don't actually
    333   // have a way to track their liveness.
    334   if (isa<AllocaRegion>(MR))
    335     return true;
    336 
    337   if (isa<CXXThisRegion>(MR))
    338     return true;
    339 
    340   if (isa<MemSpaceRegion>(MR))
    341     return true;
    342 
    343   return false;
    344 }
    345 
    346 bool SymbolReaper::isLive(SymbolRef sym) {
    347   if (TheLiving.count(sym)) {
    348     markDependentsLive(sym);
    349     return true;
    350   }
    351 
    352   if (const SymbolDerived *derived = dyn_cast<SymbolDerived>(sym)) {
    353     if (isLive(derived->getParentSymbol())) {
    354       markLive(sym);
    355       return true;
    356     }
    357     return false;
    358   }
    359 
    360   if (const SymbolExtent *extent = dyn_cast<SymbolExtent>(sym)) {
    361     if (isLiveRegion(extent->getRegion())) {
    362       markLive(sym);
    363       return true;
    364     }
    365     return false;
    366   }
    367 
    368   if (const SymbolMetadata *metadata = dyn_cast<SymbolMetadata>(sym)) {
    369     if (MetadataInUse.count(sym)) {
    370       if (isLiveRegion(metadata->getRegion())) {
    371         markLive(sym);
    372         MetadataInUse.erase(sym);
    373         return true;
    374       }
    375     }
    376     return false;
    377   }
    378 
    379   // Interogate the symbol.  It may derive from an input value to
    380   // the analyzed function/method.
    381   return isa<SymbolRegionValue>(sym);
    382 }
    383 
    384 bool SymbolReaper::isLive(const Stmt *ExprVal) const {
    385   return LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, ExprVal);
    386 }
    387 
    388 bool SymbolReaper::isLive(const VarRegion *VR, bool includeStoreBindings) const{
    389   const StackFrameContext *VarContext = VR->getStackFrame();
    390   const StackFrameContext *CurrentContext = LCtx->getCurrentStackFrame();
    391 
    392   if (VarContext == CurrentContext) {
    393     if (LCtx->getAnalysis<RelaxedLiveVariables>()->isLive(Loc, VR->getDecl()))
    394       return true;
    395 
    396     if (!includeStoreBindings)
    397       return false;
    398 
    399     unsigned &cachedQuery =
    400       const_cast<SymbolReaper*>(this)->includedRegionCache[VR];
    401 
    402     if (cachedQuery) {
    403       return cachedQuery == 1;
    404     }
    405 
    406     // Query the store to see if the region occurs in any live bindings.
    407     if (Store store = reapedStore.getStore()) {
    408       bool hasRegion =
    409         reapedStore.getStoreManager().includedInBindings(store, VR);
    410       cachedQuery = hasRegion ? 1 : 2;
    411       return hasRegion;
    412     }
    413 
    414     return false;
    415   }
    416 
    417   return VarContext->isParentOf(CurrentContext);
    418 }
    419 
    420 SymbolVisitor::~SymbolVisitor() {}
    421