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      1 //===--- ScopeInfo.cpp - Information about a semantic context -------------===//
      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 implements FunctionScopeInfo and its subclasses, which contain
     11 // information about a single function, block, lambda, or method body.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "clang/Sema/ScopeInfo.h"
     16 #include "clang/AST/Decl.h"
     17 #include "clang/AST/DeclCXX.h"
     18 #include "clang/AST/DeclObjC.h"
     19 #include "clang/AST/Expr.h"
     20 #include "clang/AST/ExprCXX.h"
     21 #include "clang/AST/ExprObjC.h"
     22 
     23 using namespace clang;
     24 using namespace sema;
     25 
     26 void FunctionScopeInfo::Clear() {
     27   HasBranchProtectedScope = false;
     28   HasBranchIntoScope = false;
     29   HasIndirectGoto = false;
     30   HasDroppedStmt = false;
     31   ObjCShouldCallSuper = false;
     32   ObjCIsDesignatedInit = false;
     33   ObjCWarnForNoDesignatedInitChain = false;
     34   ObjCIsSecondaryInit = false;
     35   ObjCWarnForNoInitDelegation = false;
     36   FirstReturnLoc = SourceLocation();
     37   FirstCXXTryLoc = SourceLocation();
     38   FirstSEHTryLoc = SourceLocation();
     39 
     40   SwitchStack.clear();
     41   Returns.clear();
     42   CoroutinePromise = nullptr;
     43   CoroutineStmts.clear();
     44   ErrorTrap.reset();
     45   PossiblyUnreachableDiags.clear();
     46   WeakObjectUses.clear();
     47   ModifiedNonNullParams.clear();
     48 }
     49 
     50 static const NamedDecl *getBestPropertyDecl(const ObjCPropertyRefExpr *PropE) {
     51   if (PropE->isExplicitProperty())
     52     return PropE->getExplicitProperty();
     53 
     54   return PropE->getImplicitPropertyGetter();
     55 }
     56 
     57 FunctionScopeInfo::WeakObjectProfileTy::BaseInfoTy
     58 FunctionScopeInfo::WeakObjectProfileTy::getBaseInfo(const Expr *E) {
     59   E = E->IgnoreParenCasts();
     60 
     61   const NamedDecl *D = nullptr;
     62   bool IsExact = false;
     63 
     64   switch (E->getStmtClass()) {
     65   case Stmt::DeclRefExprClass:
     66     D = cast<DeclRefExpr>(E)->getDecl();
     67     IsExact = isa<VarDecl>(D);
     68     break;
     69   case Stmt::MemberExprClass: {
     70     const MemberExpr *ME = cast<MemberExpr>(E);
     71     D = ME->getMemberDecl();
     72     IsExact = isa<CXXThisExpr>(ME->getBase()->IgnoreParenImpCasts());
     73     break;
     74   }
     75   case Stmt::ObjCIvarRefExprClass: {
     76     const ObjCIvarRefExpr *IE = cast<ObjCIvarRefExpr>(E);
     77     D = IE->getDecl();
     78     IsExact = IE->getBase()->isObjCSelfExpr();
     79     break;
     80   }
     81   case Stmt::PseudoObjectExprClass: {
     82     const PseudoObjectExpr *POE = cast<PseudoObjectExpr>(E);
     83     const ObjCPropertyRefExpr *BaseProp =
     84       dyn_cast<ObjCPropertyRefExpr>(POE->getSyntacticForm());
     85     if (BaseProp) {
     86       D = getBestPropertyDecl(BaseProp);
     87 
     88       const Expr *DoubleBase = BaseProp->getBase();
     89       if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(DoubleBase))
     90         DoubleBase = OVE->getSourceExpr();
     91 
     92       IsExact = DoubleBase->isObjCSelfExpr();
     93     }
     94     break;
     95   }
     96   default:
     97     break;
     98   }
     99 
    100   return BaseInfoTy(D, IsExact);
    101 }
    102 
    103 bool CapturingScopeInfo::isVLATypeCaptured(const VariableArrayType *VAT) const {
    104   RecordDecl *RD = nullptr;
    105   if (auto *LSI = dyn_cast<LambdaScopeInfo>(this))
    106     RD = LSI->Lambda;
    107   else if (auto CRSI = dyn_cast<CapturedRegionScopeInfo>(this))
    108     RD = CRSI->TheRecordDecl;
    109 
    110   if (RD)
    111     for (auto *FD : RD->fields()) {
    112       if (FD->hasCapturedVLAType() && FD->getCapturedVLAType() == VAT)
    113         return true;
    114     }
    115   return false;
    116 }
    117 
    118 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
    119                                           const ObjCPropertyRefExpr *PropE)
    120     : Base(nullptr, true), Property(getBestPropertyDecl(PropE)) {
    121 
    122   if (PropE->isObjectReceiver()) {
    123     const OpaqueValueExpr *OVE = cast<OpaqueValueExpr>(PropE->getBase());
    124     const Expr *E = OVE->getSourceExpr();
    125     Base = getBaseInfo(E);
    126   } else if (PropE->isClassReceiver()) {
    127     Base.setPointer(PropE->getClassReceiver());
    128   } else {
    129     assert(PropE->isSuperReceiver());
    130   }
    131 }
    132 
    133 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(const Expr *BaseE,
    134                                                 const ObjCPropertyDecl *Prop)
    135     : Base(nullptr, true), Property(Prop) {
    136   if (BaseE)
    137     Base = getBaseInfo(BaseE);
    138   // else, this is a message accessing a property on super.
    139 }
    140 
    141 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
    142                                                       const DeclRefExpr *DRE)
    143   : Base(nullptr, true), Property(DRE->getDecl()) {
    144   assert(isa<VarDecl>(Property));
    145 }
    146 
    147 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
    148                                                   const ObjCIvarRefExpr *IvarE)
    149   : Base(getBaseInfo(IvarE->getBase())), Property(IvarE->getDecl()) {
    150 }
    151 
    152 void FunctionScopeInfo::recordUseOfWeak(const ObjCMessageExpr *Msg,
    153                                         const ObjCPropertyDecl *Prop) {
    154   assert(Msg && Prop);
    155   WeakUseVector &Uses =
    156     WeakObjectUses[WeakObjectProfileTy(Msg->getInstanceReceiver(), Prop)];
    157   Uses.push_back(WeakUseTy(Msg, Msg->getNumArgs() == 0));
    158 }
    159 
    160 void FunctionScopeInfo::markSafeWeakUse(const Expr *E) {
    161   E = E->IgnoreParenCasts();
    162 
    163   if (const PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(E)) {
    164     markSafeWeakUse(POE->getSyntacticForm());
    165     return;
    166   }
    167 
    168   if (const ConditionalOperator *Cond = dyn_cast<ConditionalOperator>(E)) {
    169     markSafeWeakUse(Cond->getTrueExpr());
    170     markSafeWeakUse(Cond->getFalseExpr());
    171     return;
    172   }
    173 
    174   if (const BinaryConditionalOperator *Cond =
    175         dyn_cast<BinaryConditionalOperator>(E)) {
    176     markSafeWeakUse(Cond->getCommon());
    177     markSafeWeakUse(Cond->getFalseExpr());
    178     return;
    179   }
    180 
    181   // Has this weak object been seen before?
    182   FunctionScopeInfo::WeakObjectUseMap::iterator Uses;
    183   if (const ObjCPropertyRefExpr *RefExpr = dyn_cast<ObjCPropertyRefExpr>(E)) {
    184     if (!RefExpr->isObjectReceiver())
    185       return;
    186     if (isa<OpaqueValueExpr>(RefExpr->getBase()))
    187      Uses = WeakObjectUses.find(WeakObjectProfileTy(RefExpr));
    188     else {
    189       markSafeWeakUse(RefExpr->getBase());
    190       return;
    191     }
    192   }
    193   else if (const ObjCIvarRefExpr *IvarE = dyn_cast<ObjCIvarRefExpr>(E))
    194     Uses = WeakObjectUses.find(WeakObjectProfileTy(IvarE));
    195   else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
    196     Uses = WeakObjectUses.find(WeakObjectProfileTy(DRE));
    197   else if (const ObjCMessageExpr *MsgE = dyn_cast<ObjCMessageExpr>(E)) {
    198     Uses = WeakObjectUses.end();
    199     if (const ObjCMethodDecl *MD = MsgE->getMethodDecl()) {
    200       if (const ObjCPropertyDecl *Prop = MD->findPropertyDecl()) {
    201         Uses =
    202           WeakObjectUses.find(WeakObjectProfileTy(MsgE->getInstanceReceiver(),
    203                                                   Prop));
    204       }
    205     }
    206   }
    207   else
    208     return;
    209 
    210   if (Uses == WeakObjectUses.end())
    211     return;
    212 
    213   // Has there been a read from the object using this Expr?
    214   FunctionScopeInfo::WeakUseVector::reverse_iterator ThisUse =
    215     std::find(Uses->second.rbegin(), Uses->second.rend(), WeakUseTy(E, true));
    216   if (ThisUse == Uses->second.rend())
    217     return;
    218 
    219   ThisUse->markSafe();
    220 }
    221 
    222 void LambdaScopeInfo::getPotentialVariableCapture(unsigned Idx, VarDecl *&VD,
    223                                                   Expr *&E) const {
    224   assert(Idx < getNumPotentialVariableCaptures() &&
    225          "Index of potential capture must be within 0 to less than the "
    226          "number of captures!");
    227   E = PotentiallyCapturingExprs[Idx];
    228   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
    229     VD = dyn_cast<VarDecl>(DRE->getFoundDecl());
    230   else if (MemberExpr *ME = dyn_cast<MemberExpr>(E))
    231     VD = dyn_cast<VarDecl>(ME->getMemberDecl());
    232   else
    233     llvm_unreachable("Only DeclRefExprs or MemberExprs should be added for "
    234     "potential captures");
    235   assert(VD);
    236 }
    237 
    238 FunctionScopeInfo::~FunctionScopeInfo() { }
    239 BlockScopeInfo::~BlockScopeInfo() { }
    240 CapturedRegionScopeInfo::~CapturedRegionScopeInfo() { }
    241