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