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 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
116                                           const ObjCPropertyRefExpr *PropE)
117     : Base(nullptr, true), Property(getBestPropertyDecl(PropE)) {
118 
119   if (PropE->isObjectReceiver()) {
120     const OpaqueValueExpr *OVE = cast<OpaqueValueExpr>(PropE->getBase());
121     const Expr *E = OVE->getSourceExpr();
122     Base = getBaseInfo(E);
123   } else if (PropE->isClassReceiver()) {
124     Base.setPointer(PropE->getClassReceiver());
125   } else {
126     assert(PropE->isSuperReceiver());
127   }
128 }
129 
130 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(const Expr *BaseE,
131                                                 const ObjCPropertyDecl *Prop)
132     : Base(nullptr, true), Property(Prop) {
133   if (BaseE)
134     Base = getBaseInfo(BaseE);
135   // else, this is a message accessing a property on super.
136 }
137 
138 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
139                                                       const DeclRefExpr *DRE)
140   : Base(nullptr, true), Property(DRE->getDecl()) {
141   assert(isa<VarDecl>(Property));
142 }
143 
144 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy(
145                                                   const ObjCIvarRefExpr *IvarE)
146   : Base(getBaseInfo(IvarE->getBase())), Property(IvarE->getDecl()) {
147 }
148 
149 void FunctionScopeInfo::recordUseOfWeak(const ObjCMessageExpr *Msg,
150                                         const ObjCPropertyDecl *Prop) {
151   assert(Msg && Prop);
152   WeakUseVector &Uses =
153     WeakObjectUses[WeakObjectProfileTy(Msg->getInstanceReceiver(), Prop)];
154   Uses.push_back(WeakUseTy(Msg, Msg->getNumArgs() == 0));
155 }
156 
157 void FunctionScopeInfo::markSafeWeakUse(const Expr *E) {
158   E = E->IgnoreParenCasts();
159 
160   if (const PseudoObjectExpr *POE = dyn_cast<PseudoObjectExpr>(E)) {
161     markSafeWeakUse(POE->getSyntacticForm());
162     return;
163   }
164 
165   if (const ConditionalOperator *Cond = dyn_cast<ConditionalOperator>(E)) {
166     markSafeWeakUse(Cond->getTrueExpr());
167     markSafeWeakUse(Cond->getFalseExpr());
168     return;
169   }
170 
171   if (const BinaryConditionalOperator *Cond =
172         dyn_cast<BinaryConditionalOperator>(E)) {
173     markSafeWeakUse(Cond->getCommon());
174     markSafeWeakUse(Cond->getFalseExpr());
175     return;
176   }
177 
178   // Has this weak object been seen before?
179   FunctionScopeInfo::WeakObjectUseMap::iterator Uses = WeakObjectUses.end();
180   if (const ObjCPropertyRefExpr *RefExpr = dyn_cast<ObjCPropertyRefExpr>(E)) {
181     if (!RefExpr->isObjectReceiver())
182       return;
183     if (isa<OpaqueValueExpr>(RefExpr->getBase()))
184      Uses = WeakObjectUses.find(WeakObjectProfileTy(RefExpr));
185     else {
186       markSafeWeakUse(RefExpr->getBase());
187       return;
188     }
189   }
190   else if (const ObjCIvarRefExpr *IvarE = dyn_cast<ObjCIvarRefExpr>(E))
191     Uses = WeakObjectUses.find(WeakObjectProfileTy(IvarE));
192   else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
193     if (isa<VarDecl>(DRE->getDecl()))
194       Uses = WeakObjectUses.find(WeakObjectProfileTy(DRE));
195   } else if (const ObjCMessageExpr *MsgE = dyn_cast<ObjCMessageExpr>(E)) {
196     if (const ObjCMethodDecl *MD = MsgE->getMethodDecl()) {
197       if (const ObjCPropertyDecl *Prop = MD->findPropertyDecl()) {
198         Uses =
199           WeakObjectUses.find(WeakObjectProfileTy(MsgE->getInstanceReceiver(),
200                                                   Prop));
201       }
202     }
203   }
204   else
205     return;
206 
207   if (Uses == WeakObjectUses.end())
208     return;
209 
210   // Has there been a read from the object using this Expr?
211   FunctionScopeInfo::WeakUseVector::reverse_iterator ThisUse =
212       llvm::find(llvm::reverse(Uses->second), WeakUseTy(E, true));
213   if (ThisUse == Uses->second.rend())
214     return;
215 
216   ThisUse->markSafe();
217 }
218 
219 bool Capture::isInitCapture() const {
220   // Note that a nested capture of an init-capture is not itself an
221   // init-capture.
222   return !isNested() && isVariableCapture() && getVariable()->isInitCapture();
223 }
224 
225 bool CapturingScopeInfo::isVLATypeCaptured(const VariableArrayType *VAT) const {
226   for (auto &Cap : Captures)
227     if (Cap.isVLATypeCapture() && Cap.getCapturedVLAType() == VAT)
228       return true;
229   return false;
230 }
231 
232 void LambdaScopeInfo::visitPotentialCaptures(
233     llvm::function_ref<void(VarDecl *, Expr *)> Callback) const {
234   for (Expr *E : PotentiallyCapturingExprs) {
235     if (auto *DRE = dyn_cast<DeclRefExpr>(E)) {
236       Callback(cast<VarDecl>(DRE->getFoundDecl()), E);
237     } else if (auto *ME = dyn_cast<MemberExpr>(E)) {
238       Callback(cast<VarDecl>(ME->getMemberDecl()), E);
239     } else if (auto *FP = dyn_cast<FunctionParmPackExpr>(E)) {
240       for (VarDecl *VD : *FP)
241         Callback(VD, E);
242     } else {
243       llvm_unreachable("unexpected expression in potential captures list");
244     }
245   }
246 }
247 
248 FunctionScopeInfo::~FunctionScopeInfo() { }
249 BlockScopeInfo::~BlockScopeInfo() { }
250 CapturedRegionScopeInfo::~CapturedRegionScopeInfo() { }
251