1 //===--- ScopeInfo.cpp - Information about a semantic context -------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements FunctionScopeInfo and its subclasses, which contain
10 // information about a single function, block, lambda, or method body.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "clang/Sema/ScopeInfo.h"
15 #include "clang/AST/Decl.h"
16 #include "clang/AST/DeclCXX.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   HasOMPDeclareReductionCombiner = false;
31   HasFallthroughStmt = false;
32   HasPotentialAvailabilityViolations = false;
33   ObjCShouldCallSuper = false;
34   ObjCIsDesignatedInit = false;
35   ObjCWarnForNoDesignatedInitChain = false;
36   ObjCIsSecondaryInit = false;
37   ObjCWarnForNoInitDelegation = false;
38   FirstReturnLoc = SourceLocation();
39   FirstCXXTryLoc = SourceLocation();
40   FirstSEHTryLoc = SourceLocation();
41 
42   // Coroutine state
43   FirstCoroutineStmtLoc = SourceLocation();
44   CoroutinePromise = nullptr;
45   CoroutineParameterMoves.clear();
46   NeedsCoroutineSuspends = true;
47   CoroutineSuspends.first = nullptr;
48   CoroutineSuspends.second = nullptr;
49 
50   SwitchStack.clear();
51   Returns.clear();
52   ErrorTrap.reset();
53   PossiblyUnreachableDiags.clear();
54   WeakObjectUses.clear();
55   ModifiedNonNullParams.clear();
56   Blocks.clear();
57   ByrefBlockVars.clear();
58 }
59 
60 static const NamedDecl *getBestPropertyDecl(const ObjCPropertyRefExpr *PropE) {
61   if (PropE->isExplicitProperty())
62     return PropE->getExplicitProperty();
63 
64   return PropE->getImplicitPropertyGetter();
65 }
66 
67 FunctionScopeInfo::WeakObjectProfileTy::BaseInfoTy
68 FunctionScopeInfo::WeakObjectProfileTy::getBaseInfo(const Expr *E) {
69   E = E->IgnoreParenCasts();
70 
71   const NamedDecl *D = nullptr;
72   bool IsExact = false;
73 
74   switch (E->getStmtClass()) {
75   case Stmt::DeclRefExprClass:
76     D = cast<DeclRefExpr>(E)->getDecl();
77     IsExact = isa<VarDecl>(D);
78     break;
79   case Stmt::MemberExprClass: {
80     const MemberExpr *ME = cast<MemberExpr>(E);
81     D = ME->getMemberDecl();
82     IsExact = isa<CXXThisExpr>(ME->getBase()->IgnoreParenImpCasts());
83     break;
84   }
85   case Stmt::ObjCIvarRefExprClass: {
86     const ObjCIvarRefExpr *IE = cast<ObjCIvarRefExpr>(E);
87     D = IE->getDecl();
88     IsExact = IE->getBase()->isObjCSelfExpr();
89     break;
90   }
91   case Stmt::PseudoObjectExprClass: {
92     const PseudoObjectExpr *POE = cast<PseudoObjectExpr>(E);
93     const ObjCPropertyRefExpr *BaseProp =
94       dyn_cast<ObjCPropertyRefExpr>(POE->getSyntacticForm());
95     if (BaseProp) {
96       D = getBestPropertyDecl(BaseProp);
97 
98       if (BaseProp->isObjectReceiver()) {
99         const Expr *DoubleBase = BaseProp->getBase();
100         if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(DoubleBase))
101           DoubleBase = OVE->getSourceExpr();
102 
103         IsExact = DoubleBase->isObjCSelfExpr();
104       }
105     }
106     break;
107   }
108   default:
109     break;
110   }
111 
112   return BaseInfoTy(D, IsExact);
113 }
114 
115 bool CapturingScopeInfo::isVLATypeCaptured(const VariableArrayType *VAT) const {
116   RecordDecl *RD = nullptr;
117   if (auto *LSI = dyn_cast<LambdaScopeInfo>(this))
118     RD = LSI->Lambda;
119   else if (auto CRSI = dyn_cast<CapturedRegionScopeInfo>(this))
120     RD = CRSI->TheRecordDecl;
121 
122   if (RD)
123     for (auto *FD : RD->fields()) {
124       if (FD->hasCapturedVLAType() && FD->getCapturedVLAType() == VAT)
125         return true;
126     }
127   return false;
128 }
129 
130 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
131                                           const ObjCPropertyRefExpr *PropE)
132     : Base(nullptr, true), Property(getBestPropertyDecl(PropE)) {
133 
134   if (PropE->isObjectReceiver()) {
135     const OpaqueValueExpr *OVE = cast<OpaqueValueExpr>(PropE->getBase());
136     const Expr *E = OVE->getSourceExpr();
137     Base = getBaseInfo(E);
138   } else if (PropE->isClassReceiver()) {
139     Base.setPointer(PropE->getClassReceiver());
140   } else {
141     assert(PropE->isSuperReceiver());
142   }
143 }
144 
145 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(const Expr *BaseE,
146                                                 const ObjCPropertyDecl *Prop)
147     : Base(nullptr, true), Property(Prop) {
148   if (BaseE)
149     Base = getBaseInfo(BaseE);
150   // else, this is a message accessing a property on super.
151 }
152 
153 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
154                                                       const DeclRefExpr *DRE)
155   : Base(nullptr, true), Property(DRE->getDecl()) {
156   assert(isa<VarDecl>(Property));
157 }
158 
159 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
160                                                   const ObjCIvarRefExpr *IvarE)
161   : Base(getBaseInfo(IvarE->getBase())), Property(IvarE->getDecl()) {
162 }
163 
164 void FunctionScopeInfo::recordUseOfWeak(const ObjCMessageExpr *Msg,
165                                         const ObjCPropertyDecl *Prop) {
166   assert(Msg && Prop);
167   WeakUseVector &Uses =
168     WeakObjectUses[WeakObjectProfileTy(Msg->getInstanceReceiver(), Prop)];
169   Uses.push_back(WeakUseTy(Msg, Msg->getNumArgs() == 0));
170 }
171 
172 void FunctionScopeInfo::markSafeWeakUse(const Expr *E) {
173   E = E->IgnoreParenCasts();
174 
175   if (const PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(E)) {
176     markSafeWeakUse(POE->getSyntacticForm());
177     return;
178   }
179 
180   if (const ConditionalOperator *Cond = dyn_cast<ConditionalOperator>(E)) {
181     markSafeWeakUse(Cond->getTrueExpr());
182     markSafeWeakUse(Cond->getFalseExpr());
183     return;
184   }
185 
186   if (const BinaryConditionalOperator *Cond =
187         dyn_cast<BinaryConditionalOperator>(E)) {
188     markSafeWeakUse(Cond->getCommon());
189     markSafeWeakUse(Cond->getFalseExpr());
190     return;
191   }
192 
193   // Has this weak object been seen before?
194   FunctionScopeInfo::WeakObjectUseMap::iterator Uses = WeakObjectUses.end();
195   if (const ObjCPropertyRefExpr *RefExpr = dyn_cast<ObjCPropertyRefExpr>(E)) {
196     if (!RefExpr->isObjectReceiver())
197       return;
198     if (isa<OpaqueValueExpr>(RefExpr->getBase()))
199      Uses = WeakObjectUses.find(WeakObjectProfileTy(RefExpr));
200     else {
201       markSafeWeakUse(RefExpr->getBase());
202       return;
203     }
204   }
205   else if (const ObjCIvarRefExpr *IvarE = dyn_cast<ObjCIvarRefExpr>(E))
206     Uses = WeakObjectUses.find(WeakObjectProfileTy(IvarE));
207   else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
208     if (isa<VarDecl>(DRE->getDecl()))
209       Uses = WeakObjectUses.find(WeakObjectProfileTy(DRE));
210   } else if (const ObjCMessageExpr *MsgE = dyn_cast<ObjCMessageExpr>(E)) {
211     if (const ObjCMethodDecl *MD = MsgE->getMethodDecl()) {
212       if (const ObjCPropertyDecl *Prop = MD->findPropertyDecl()) {
213         Uses =
214           WeakObjectUses.find(WeakObjectProfileTy(MsgE->getInstanceReceiver(),
215                                                   Prop));
216       }
217     }
218   }
219   else
220     return;
221 
222   if (Uses == WeakObjectUses.end())
223     return;
224 
225   // Has there been a read from the object using this Expr?
226   FunctionScopeInfo::WeakUseVector::reverse_iterator ThisUse =
227       llvm::find(llvm::reverse(Uses->second), WeakUseTy(E, true));
228   if (ThisUse == Uses->second.rend())
229     return;
230 
231   ThisUse->markSafe();
232 }
233 
234 void LambdaScopeInfo::getPotentialVariableCapture(unsigned Idx, VarDecl *&VD,
235                                                   Expr *&E) const {
236   assert(Idx < getNumPotentialVariableCaptures() &&
237          "Index of potential capture must be within 0 to less than the "
238          "number of captures!");
239   E = PotentiallyCapturingExprs[Idx];
240   if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
241     VD = dyn_cast<VarDecl>(DRE->getFoundDecl());
242   else if (MemberExpr *ME = dyn_cast<MemberExpr>(E))
243     VD = dyn_cast<VarDecl>(ME->getMemberDecl());
244   else
245     llvm_unreachable("Only DeclRefExprs or MemberExprs should be added for "
246     "potential captures");
247   assert(VD);
248 }
249 
250 FunctionScopeInfo::~FunctionScopeInfo() { }
251 BlockScopeInfo::~BlockScopeInfo() { }
252 CapturedRegionScopeInfo::~CapturedRegionScopeInfo() { }
253