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