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