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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   HasOMPDeclareReductionCombiner = false;
     32   ObjCShouldCallSuper = false;
     33   ObjCIsDesignatedInit = false;
     34   ObjCWarnForNoDesignatedInitChain = false;
     35   ObjCIsSecondaryInit = false;
     36   ObjCWarnForNoInitDelegation = false;
     37   FirstReturnLoc = SourceLocation();
     38   FirstCXXTryLoc = SourceLocation();
     39   FirstSEHTryLoc = SourceLocation();
     40 
     41   SwitchStack.clear();
     42   Returns.clear();
     43   CoroutinePromise = nullptr;
     44   CoroutineStmts.clear();
     45   ErrorTrap.reset();
     46   PossiblyUnreachableDiags.clear();
     47   WeakObjectUses.clear();
     48   ModifiedNonNullParams.clear();
     49 }
     50 
     51 static const NamedDecl *getBestPropertyDecl(const ObjCPropertyRefExpr *PropE) {
     52   if (PropE->isExplicitProperty())
     53     return PropE->getExplicitProperty();
     54 
     55   return PropE->getImplicitPropertyGetter();
     56 }
     57 
     58 FunctionScopeInfo::WeakObjectProfileTy::BaseInfoTy
     59 FunctionScopeInfo::WeakObjectProfileTy::getBaseInfo(const Expr *E) {
     60   E = E->IgnoreParenCasts();
     61 
     62   const NamedDecl *D = nullptr;
     63   bool IsExact = false;
     64 
     65   switch (E->getStmtClass()) {
     66   case Stmt::DeclRefExprClass:
     67     D = cast<DeclRefExpr>(E)->getDecl();
     68     IsExact = isa<VarDecl>(D);
     69     break;
     70   case Stmt::MemberExprClass: {
     71     const MemberExpr *ME = cast<MemberExpr>(E);
     72     D = ME->getMemberDecl();
     73     IsExact = isa<CXXThisExpr>(ME->getBase()->IgnoreParenImpCasts());
     74     break;
     75   }
     76   case Stmt::ObjCIvarRefExprClass: {
     77     const ObjCIvarRefExpr *IE = cast<ObjCIvarRefExpr>(E);
     78     D = IE->getDecl();
     79     IsExact = IE->getBase()->isObjCSelfExpr();
     80     break;
     81   }
     82   case Stmt::PseudoObjectExprClass: {
     83     const PseudoObjectExpr *POE = cast<PseudoObjectExpr>(E);
     84     const ObjCPropertyRefExpr *BaseProp =
     85       dyn_cast<ObjCPropertyRefExpr>(POE->getSyntacticForm());
     86     if (BaseProp) {
     87       D = getBestPropertyDecl(BaseProp);
     88 
     89       if (BaseProp->isObjectReceiver()) {
     90         const Expr *DoubleBase = BaseProp->getBase();
     91         if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(DoubleBase))
     92           DoubleBase = OVE->getSourceExpr();
     93 
     94         IsExact = DoubleBase->isObjCSelfExpr();
     95       }
     96     }
     97     break;
     98   }
     99   default:
    100     break;
    101   }
    102 
    103   return BaseInfoTy(D, IsExact);
    104 }
    105 
    106 bool CapturingScopeInfo::isVLATypeCaptured(const VariableArrayType *VAT) const {
    107   RecordDecl *RD = nullptr;
    108   if (auto *LSI = dyn_cast<LambdaScopeInfo>(this))
    109     RD = LSI->Lambda;
    110   else if (auto CRSI = dyn_cast<CapturedRegionScopeInfo>(this))
    111     RD = CRSI->TheRecordDecl;
    112 
    113   if (RD)
    114     for (auto *FD : RD->fields()) {
    115       if (FD->hasCapturedVLAType() && FD->getCapturedVLAType() == VAT)
    116         return true;
    117     }
    118   return false;
    119 }
    120 
    121 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
    122                                           const ObjCPropertyRefExpr *PropE)
    123     : Base(nullptr, true), Property(getBestPropertyDecl(PropE)) {
    124 
    125   if (PropE->isObjectReceiver()) {
    126     const OpaqueValueExpr *OVE = cast<OpaqueValueExpr>(PropE->getBase());
    127     const Expr *E = OVE->getSourceExpr();
    128     Base = getBaseInfo(E);
    129   } else if (PropE->isClassReceiver()) {
    130     Base.setPointer(PropE->getClassReceiver());
    131   } else {
    132     assert(PropE->isSuperReceiver());
    133   }
    134 }
    135 
    136 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(const Expr *BaseE,
    137                                                 const ObjCPropertyDecl *Prop)
    138     : Base(nullptr, true), Property(Prop) {
    139   if (BaseE)
    140     Base = getBaseInfo(BaseE);
    141   // else, this is a message accessing a property on super.
    142 }
    143 
    144 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
    145                                                       const DeclRefExpr *DRE)
    146   : Base(nullptr, true), Property(DRE->getDecl()) {
    147   assert(isa<VarDecl>(Property));
    148 }
    149 
    150 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
    151                                                   const ObjCIvarRefExpr *IvarE)
    152   : Base(getBaseInfo(IvarE->getBase())), Property(IvarE->getDecl()) {
    153 }
    154 
    155 void FunctionScopeInfo::recordUseOfWeak(const ObjCMessageExpr *Msg,
    156                                         const ObjCPropertyDecl *Prop) {
    157   assert(Msg && Prop);
    158   WeakUseVector &Uses =
    159     WeakObjectUses[WeakObjectProfileTy(Msg->getInstanceReceiver(), Prop)];
    160   Uses.push_back(WeakUseTy(Msg, Msg->getNumArgs() == 0));
    161 }
    162 
    163 void FunctionScopeInfo::markSafeWeakUse(const Expr *E) {
    164   E = E->IgnoreParenCasts();
    165 
    166   if (const PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(E)) {
    167     markSafeWeakUse(POE->getSyntacticForm());
    168     return;
    169   }
    170 
    171   if (const ConditionalOperator *Cond = dyn_cast<ConditionalOperator>(E)) {
    172     markSafeWeakUse(Cond->getTrueExpr());
    173     markSafeWeakUse(Cond->getFalseExpr());
    174     return;
    175   }
    176 
    177   if (const BinaryConditionalOperator *Cond =
    178         dyn_cast<BinaryConditionalOperator>(E)) {
    179     markSafeWeakUse(Cond->getCommon());
    180     markSafeWeakUse(Cond->getFalseExpr());
    181     return;
    182   }
    183 
    184   // Has this weak object been seen before?
    185   FunctionScopeInfo::WeakObjectUseMap::iterator Uses;
    186   if (const ObjCPropertyRefExpr *RefExpr = dyn_cast<ObjCPropertyRefExpr>(E)) {
    187     if (!RefExpr->isObjectReceiver())
    188       return;
    189     if (isa<OpaqueValueExpr>(RefExpr->getBase()))
    190      Uses = WeakObjectUses.find(WeakObjectProfileTy(RefExpr));
    191     else {
    192       markSafeWeakUse(RefExpr->getBase());
    193       return;
    194     }
    195   }
    196   else if (const ObjCIvarRefExpr *IvarE = dyn_cast<ObjCIvarRefExpr>(E))
    197     Uses = WeakObjectUses.find(WeakObjectProfileTy(IvarE));
    198   else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
    199     Uses = WeakObjectUses.find(WeakObjectProfileTy(DRE));
    200   else if (const ObjCMessageExpr *MsgE = dyn_cast<ObjCMessageExpr>(E)) {
    201     Uses = WeakObjectUses.end();
    202     if (const ObjCMethodDecl *MD = MsgE->getMethodDecl()) {
    203       if (const ObjCPropertyDecl *Prop = MD->findPropertyDecl()) {
    204         Uses =
    205           WeakObjectUses.find(WeakObjectProfileTy(MsgE->getInstanceReceiver(),
    206                                                   Prop));
    207       }
    208     }
    209   }
    210   else
    211     return;
    212 
    213   if (Uses == WeakObjectUses.end())
    214     return;
    215 
    216   // Has there been a read from the object using this Expr?
    217   FunctionScopeInfo::WeakUseVector::reverse_iterator ThisUse =
    218       llvm::find(llvm::reverse(Uses->second), WeakUseTy(E, true));
    219   if (ThisUse == Uses->second.rend())
    220     return;
    221 
    222   ThisUse->markSafe();
    223 }
    224 
    225 void LambdaScopeInfo::getPotentialVariableCapture(unsigned Idx, VarDecl *&VD,
    226                                                   Expr *&E) const {
    227   assert(Idx < getNumPotentialVariableCaptures() &&
    228          "Index of potential capture must be within 0 to less than the "
    229          "number of captures!");
    230   E = PotentiallyCapturingExprs[Idx];
    231   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
    232     VD = dyn_cast<VarDecl>(DRE->getFoundDecl());
    233   else if (MemberExpr *ME = dyn_cast<MemberExpr>(E))
    234     VD = dyn_cast<VarDecl>(ME->getMemberDecl());
    235   else
    236     llvm_unreachable("Only DeclRefExprs or MemberExprs should be added for "
    237     "potential captures");
    238   assert(VD);
    239 }
    240 
    241 FunctionScopeInfo::~FunctionScopeInfo() { }
    242 BlockScopeInfo::~BlockScopeInfo() { }
    243 CapturedRegionScopeInfo::~CapturedRegionScopeInfo() { }
    244