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     Uses = WeakObjectUses.find(WeakObjectProfileTy(RefExpr));
163   else if (const ObjCIvarRefExpr *IvarE = dyn_cast<ObjCIvarRefExpr>(E))
164     Uses = WeakObjectUses.find(WeakObjectProfileTy(IvarE));
165   else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
166     Uses = WeakObjectUses.find(WeakObjectProfileTy(DRE));
167   else if (const ObjCMessageExpr *MsgE = dyn_cast<ObjCMessageExpr>(E)) {
168     Uses = WeakObjectUses.end();
169     if (const ObjCMethodDecl *MD = MsgE->getMethodDecl()) {
170       if (const ObjCPropertyDecl *Prop = MD->findPropertyDecl()) {
171         Uses =
172           WeakObjectUses.find(WeakObjectProfileTy(MsgE->getInstanceReceiver(),
173                                                   Prop));
174       }
175     }
176   }
177   else
178     return;
179 
180   if (Uses == WeakObjectUses.end())
181     return;
182 
183   // Has there been a read from the object using this Expr?
184   FunctionScopeInfo::WeakUseVector::reverse_iterator ThisUse =
185     std::find(Uses->second.rbegin(), Uses->second.rend(), WeakUseTy(E, true));
186   if (ThisUse == Uses->second.rend())
187     return;
188 
189   ThisUse->markSafe();
190 }
191 
192 void LambdaScopeInfo::getPotentialVariableCapture(unsigned Idx, VarDecl *&VD,
193                                                   Expr *&E) const {
194   assert(Idx < getNumPotentialVariableCaptures() &&
195          "Index of potential capture must be within 0 to less than the "
196          "number of captures!");
197   E = PotentiallyCapturingExprs[Idx];
198   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
199     VD = dyn_cast<VarDecl>(DRE->getFoundDecl());
200   else if (MemberExpr *ME = dyn_cast<MemberExpr>(E))
201     VD = dyn_cast<VarDecl>(ME->getMemberDecl());
202   else
203     llvm_unreachable("Only DeclRefExprs or MemberExprs should be added for "
204     "potential captures");
205   assert(VD);
206 }
207 
208 FunctionScopeInfo::~FunctionScopeInfo() { }
209 BlockScopeInfo::~BlockScopeInfo() { }
210 LambdaScopeInfo::~LambdaScopeInfo() { }
211 CapturedRegionScopeInfo::~CapturedRegionScopeInfo() { }
212