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   UsesFPIntrin = false;
33   HasPotentialAvailabilityViolations = false;
34   ObjCShouldCallSuper = false;
35   ObjCIsDesignatedInit = false;
36   ObjCWarnForNoDesignatedInitChain = false;
37   ObjCIsSecondaryInit = false;
38   ObjCWarnForNoInitDelegation = false;
39   FirstReturnLoc = SourceLocation();
40   FirstCXXOrObjCTryLoc = SourceLocation();
41   FirstSEHTryLoc = SourceLocation();
42 
43   // Coroutine state
44   FirstCoroutineStmtLoc = SourceLocation();
45   CoroutinePromise = nullptr;
46   CoroutineParameterMoves.clear();
47   NeedsCoroutineSuspends = true;
48   CoroutineSuspends.first = nullptr;
49   CoroutineSuspends.second = nullptr;
50 
51   SwitchStack.clear();
52   Returns.clear();
53   ErrorTrap.reset();
54   PossiblyUnreachableDiags.clear();
55   WeakObjectUses.clear();
56   ModifiedNonNullParams.clear();
57   Blocks.clear();
58   ByrefBlockVars.clear();
59 }
60 
61 static const NamedDecl *getBestPropertyDecl(const ObjCPropertyRefExpr *PropE) {
62   if (PropE->isExplicitProperty())
63     return PropE->getExplicitProperty();
64 
65   return PropE->getImplicitPropertyGetter();
66 }
67 
68 FunctionScopeInfo::WeakObjectProfileTy::BaseInfoTy
69 FunctionScopeInfo::WeakObjectProfileTy::getBaseInfo(const Expr *E) {
70   E = E->IgnoreParenCasts();
71 
72   const NamedDecl *D = nullptr;
73   bool IsExact = false;
74 
75   switch (E->getStmtClass()) {
76   case Stmt::DeclRefExprClass:
77     D = cast<DeclRefExpr>(E)->getDecl();
78     IsExact = isa<VarDecl>(D);
79     break;
80   case Stmt::MemberExprClass: {
81     const MemberExpr *ME = cast<MemberExpr>(E);
82     D = ME->getMemberDecl();
83     IsExact = isa<CXXThisExpr>(ME->getBase()->IgnoreParenImpCasts());
84     break;
85   }
86   case Stmt::ObjCIvarRefExprClass: {
87     const ObjCIvarRefExpr *IE = cast<ObjCIvarRefExpr>(E);
88     D = IE->getDecl();
89     IsExact = IE->getBase()->isObjCSelfExpr();
90     break;
91   }
92   case Stmt::PseudoObjectExprClass: {
93     const PseudoObjectExpr *POE = cast<PseudoObjectExpr>(E);
94     const ObjCPropertyRefExpr *BaseProp =
95       dyn_cast<ObjCPropertyRefExpr>(POE->getSyntacticForm());
96     if (BaseProp) {
97       D = getBestPropertyDecl(BaseProp);
98 
99       if (BaseProp->isObjectReceiver()) {
100         const Expr *DoubleBase = BaseProp->getBase();
101         if (const OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(DoubleBase))
102           DoubleBase = OVE->getSourceExpr();
103 
104         IsExact = DoubleBase->isObjCSelfExpr();
105       }
106     }
107     break;
108   }
109   default:
110     break;
111   }
112 
113   return BaseInfoTy(D, IsExact);
114 }
115 
116 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
117                                           const ObjCPropertyRefExpr *PropE)
118     : Base(nullptr, true), Property(getBestPropertyDecl(PropE)) {
119 
120   if (PropE->isObjectReceiver()) {
121     const OpaqueValueExpr *OVE = cast<OpaqueValueExpr>(PropE->getBase());
122     const Expr *E = OVE->getSourceExpr();
123     Base = getBaseInfo(E);
124   } else if (PropE->isClassReceiver()) {
125     Base.setPointer(PropE->getClassReceiver());
126   } else {
127     assert(PropE->isSuperReceiver());
128   }
129 }
130 
131 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(const Expr *BaseE,
132                                                 const ObjCPropertyDecl *Prop)
133     : Base(nullptr, true), Property(Prop) {
134   if (BaseE)
135     Base = getBaseInfo(BaseE);
136   // else, this is a message accessing a property on super.
137 }
138 
139 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
140                                                       const DeclRefExpr *DRE)
141   : Base(nullptr, true), Property(DRE->getDecl()) {
142   assert(isa<VarDecl>(Property));
143 }
144 
145 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
146                                                   const ObjCIvarRefExpr *IvarE)
147   : Base(getBaseInfo(IvarE->getBase())), Property(IvarE->getDecl()) {
148 }
149 
150 void FunctionScopeInfo::recordUseOfWeak(const ObjCMessageExpr *Msg,
151                                         const ObjCPropertyDecl *Prop) {
152   assert(Msg && Prop);
153   WeakUseVector &Uses =
154     WeakObjectUses[WeakObjectProfileTy(Msg->getInstanceReceiver(), Prop)];
155   Uses.push_back(WeakUseTy(Msg, Msg->getNumArgs() == 0));
156 }
157 
158 void FunctionScopeInfo::markSafeWeakUse(const Expr *E) {
159   E = E->IgnoreParenCasts();
160 
161   if (const PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(E)) {
162     markSafeWeakUse(POE->getSyntacticForm());
163     return;
164   }
165 
166   if (const ConditionalOperator *Cond = dyn_cast<ConditionalOperator>(E)) {
167     markSafeWeakUse(Cond->getTrueExpr());
168     markSafeWeakUse(Cond->getFalseExpr());
169     return;
170   }
171 
172   if (const BinaryConditionalOperator *Cond =
173         dyn_cast<BinaryConditionalOperator>(E)) {
174     markSafeWeakUse(Cond->getCommon());
175     markSafeWeakUse(Cond->getFalseExpr());
176     return;
177   }
178 
179   // Has this weak object been seen before?
180   FunctionScopeInfo::WeakObjectUseMap::iterator Uses = WeakObjectUses.end();
181   if (const ObjCPropertyRefExpr *RefExpr = dyn_cast<ObjCPropertyRefExpr>(E)) {
182     if (!RefExpr->isObjectReceiver())
183       return;
184     if (isa<OpaqueValueExpr>(RefExpr->getBase()))
185      Uses = WeakObjectUses.find(WeakObjectProfileTy(RefExpr));
186     else {
187       markSafeWeakUse(RefExpr->getBase());
188       return;
189     }
190   }
191   else if (const ObjCIvarRefExpr *IvarE = dyn_cast<ObjCIvarRefExpr>(E))
192     Uses = WeakObjectUses.find(WeakObjectProfileTy(IvarE));
193   else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
194     if (isa<VarDecl>(DRE->getDecl()))
195       Uses = WeakObjectUses.find(WeakObjectProfileTy(DRE));
196   } else if (const ObjCMessageExpr *MsgE = dyn_cast<ObjCMessageExpr>(E)) {
197     if (const ObjCMethodDecl *MD = MsgE->getMethodDecl()) {
198       if (const ObjCPropertyDecl *Prop = MD->findPropertyDecl()) {
199         Uses =
200           WeakObjectUses.find(WeakObjectProfileTy(MsgE->getInstanceReceiver(),
201                                                   Prop));
202       }
203     }
204   }
205   else
206     return;
207 
208   if (Uses == WeakObjectUses.end())
209     return;
210 
211   // Has there been a read from the object using this Expr?
212   FunctionScopeInfo::WeakUseVector::reverse_iterator ThisUse =
213       llvm::find(llvm::reverse(Uses->second), WeakUseTy(E, true));
214   if (ThisUse == Uses->second.rend())
215     return;
216 
217   ThisUse->markSafe();
218 }
219 
220 bool Capture::isInitCapture() const {
221   // Note that a nested capture of an init-capture is not itself an
222   // init-capture.
223   return !isNested() && isVariableCapture() && getVariable()->isInitCapture();
224 }
225 
226 bool CapturingScopeInfo::isVLATypeCaptured(const VariableArrayType *VAT) const {
227   for (auto &Cap : Captures)
228     if (Cap.isVLATypeCapture() && Cap.getCapturedVLAType() == VAT)
229       return true;
230   return false;
231 }
232 
233 void LambdaScopeInfo::visitPotentialCaptures(
234     llvm::function_ref<void(VarDecl *, Expr *)> Callback) const {
235   for (Expr *E : PotentiallyCapturingExprs) {
236     if (auto *DRE = dyn_cast<DeclRefExpr>(E)) {
237       Callback(cast<VarDecl>(DRE->getFoundDecl()), E);
238     } else if (auto *ME = dyn_cast<MemberExpr>(E)) {
239       Callback(cast<VarDecl>(ME->getMemberDecl()), E);
240     } else if (auto *FP = dyn_cast<FunctionParmPackExpr>(E)) {
241       for (VarDecl *VD : *FP)
242         Callback(VD, E);
243     } else {
244       llvm_unreachable("unexpected expression in potential captures list");
245     }
246   }
247 }
248 
249 FunctionScopeInfo::~FunctionScopeInfo() { }
250 BlockScopeInfo::~BlockScopeInfo() { }
251 CapturedRegionScopeInfo::~CapturedRegionScopeInfo() { }
252