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1 //===--- ScopeInfo.h - Information about a semantic context -----*- C++ -*-===//
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 defines FunctionScopeInfo and its subclasses, which contain
11 // information about a single function, block, lambda, or method body.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_CLANG_SEMA_SCOPEINFO_H
16 #define LLVM_CLANG_SEMA_SCOPEINFO_H
17 
18 #include "clang/AST/Expr.h"
19 #include "clang/AST/Type.h"
20 #include "clang/Basic/CapturedStmt.h"
21 #include "clang/Basic/PartialDiagnostic.h"
22 #include "clang/Sema/CleanupInfo.h"
23 #include "clang/Sema/Ownership.h"
24 #include "llvm/ADT/DenseMap.h"
25 #include "llvm/ADT/SmallSet.h"
26 #include "llvm/ADT/SmallVector.h"
27 #include <algorithm>
28 
29 namespace clang {
30 
31 class Decl;
32 class BlockDecl;
33 class CapturedDecl;
34 class CXXMethodDecl;
35 class FieldDecl;
36 class ObjCPropertyDecl;
37 class IdentifierInfo;
38 class ImplicitParamDecl;
39 class LabelDecl;
40 class ReturnStmt;
41 class Scope;
42 class SwitchStmt;
43 class TemplateTypeParmDecl;
44 class TemplateParameterList;
45 class VarDecl;
46 class ObjCIvarRefExpr;
47 class ObjCPropertyRefExpr;
48 class ObjCMessageExpr;
49 
50 namespace sema {
51 
52 /// \brief Contains information about the compound statement currently being
53 /// parsed.
54 class CompoundScopeInfo {
55 public:
CompoundScopeInfo()56   CompoundScopeInfo()
57     : HasEmptyLoopBodies(false) { }
58 
59   /// \brief Whether this compound stamement contains `for' or `while' loops
60   /// with empty bodies.
61   bool HasEmptyLoopBodies;
62 
setHasEmptyLoopBodies()63   void setHasEmptyLoopBodies() {
64     HasEmptyLoopBodies = true;
65   }
66 };
67 
68 class PossiblyUnreachableDiag {
69 public:
70   PartialDiagnostic PD;
71   SourceLocation Loc;
72   const Stmt *stmt;
73 
PossiblyUnreachableDiag(const PartialDiagnostic & PD,SourceLocation Loc,const Stmt * stmt)74   PossiblyUnreachableDiag(const PartialDiagnostic &PD, SourceLocation Loc,
75                           const Stmt *stmt)
76     : PD(PD), Loc(Loc), stmt(stmt) {}
77 };
78 
79 /// \brief Retains information about a function, method, or block that is
80 /// currently being parsed.
81 class FunctionScopeInfo {
82 protected:
83   enum ScopeKind {
84     SK_Function,
85     SK_Block,
86     SK_Lambda,
87     SK_CapturedRegion
88   };
89 
90 public:
91   /// \brief What kind of scope we are describing.
92   ///
93   ScopeKind Kind : 3;
94 
95   /// \brief Whether this function contains a VLA, \@try, try, C++
96   /// initializer, or anything else that can't be jumped past.
97   bool HasBranchProtectedScope : 1;
98 
99   /// \brief Whether this function contains any switches or direct gotos.
100   bool HasBranchIntoScope : 1;
101 
102   /// \brief Whether this function contains any indirect gotos.
103   bool HasIndirectGoto : 1;
104 
105   /// \brief Whether a statement was dropped because it was invalid.
106   bool HasDroppedStmt : 1;
107 
108   /// \brief True if current scope is for OpenMP declare reduction combiner.
109   bool HasOMPDeclareReductionCombiner;
110 
111   /// \brief Whether there is a fallthrough statement in this function.
112   bool HasFallthroughStmt : 1;
113 
114   /// A flag that is set when parsing a method that must call super's
115   /// implementation, such as \c -dealloc, \c -finalize, or any method marked
116   /// with \c __attribute__((objc_requires_super)).
117   bool ObjCShouldCallSuper : 1;
118 
119   /// True when this is a method marked as a designated initializer.
120   bool ObjCIsDesignatedInit : 1;
121   /// This starts true for a method marked as designated initializer and will
122   /// be set to false if there is an invocation to a designated initializer of
123   /// the super class.
124   bool ObjCWarnForNoDesignatedInitChain : 1;
125 
126   /// True when this is an initializer method not marked as a designated
127   /// initializer within a class that has at least one initializer marked as a
128   /// designated initializer.
129   bool ObjCIsSecondaryInit : 1;
130   /// This starts true for a secondary initializer method and will be set to
131   /// false if there is an invocation of an initializer on 'self'.
132   bool ObjCWarnForNoInitDelegation : 1;
133 
134   /// First 'return' statement in the current function.
135   SourceLocation FirstReturnLoc;
136 
137   /// First C++ 'try' statement in the current function.
138   SourceLocation FirstCXXTryLoc;
139 
140   /// First SEH '__try' statement in the current function.
141   SourceLocation FirstSEHTryLoc;
142 
143   /// \brief Used to determine if errors occurred in this function or block.
144   DiagnosticErrorTrap ErrorTrap;
145 
146   /// SwitchStack - This is the current set of active switch statements in the
147   /// block.
148   SmallVector<SwitchStmt*, 8> SwitchStack;
149 
150   /// \brief The list of return statements that occur within the function or
151   /// block, if there is any chance of applying the named return value
152   /// optimization, or if we need to infer a return type.
153   SmallVector<ReturnStmt*, 4> Returns;
154 
155   /// \brief The promise object for this coroutine, if any.
156   VarDecl *CoroutinePromise;
157 
158   /// \brief The list of coroutine control flow constructs (co_await, co_yield,
159   /// co_return) that occur within the function or block. Empty if and only if
160   /// this function or block is not (yet known to be) a coroutine.
161   SmallVector<Stmt*, 4> CoroutineStmts;
162 
163   /// \brief The stack of currently active compound stamement scopes in the
164   /// function.
165   SmallVector<CompoundScopeInfo, 4> CompoundScopes;
166 
167   /// \brief A list of PartialDiagnostics created but delayed within the
168   /// current function scope.  These diagnostics are vetted for reachability
169   /// prior to being emitted.
170   SmallVector<PossiblyUnreachableDiag, 4> PossiblyUnreachableDiags;
171 
172   /// \brief A list of parameters which have the nonnull attribute and are
173   /// modified in the function.
174   llvm::SmallPtrSet<const ParmVarDecl*, 8> ModifiedNonNullParams;
175 
176 public:
177   /// Represents a simple identification of a weak object.
178   ///
179   /// Part of the implementation of -Wrepeated-use-of-weak.
180   ///
181   /// This is used to determine if two weak accesses refer to the same object.
182   /// Here are some examples of how various accesses are "profiled":
183   ///
184   /// Access Expression |     "Base" Decl     |          "Property" Decl
185   /// :---------------: | :-----------------: | :------------------------------:
186   /// self.property     | self (VarDecl)      | property (ObjCPropertyDecl)
187   /// self.implicitProp | self (VarDecl)      | -implicitProp (ObjCMethodDecl)
188   /// self->ivar.prop   | ivar (ObjCIvarDecl) | prop (ObjCPropertyDecl)
189   /// cxxObj.obj.prop   | obj (FieldDecl)     | prop (ObjCPropertyDecl)
190   /// [self foo].prop   | 0 (unknown)         | prop (ObjCPropertyDecl)
191   /// self.prop1.prop2  | prop1 (ObjCPropertyDecl)    | prop2 (ObjCPropertyDecl)
192   /// MyClass.prop      | MyClass (ObjCInterfaceDecl) | -prop (ObjCMethodDecl)
193   /// MyClass.foo.prop  | +foo (ObjCMethodDecl)       | -prop (ObjCPropertyDecl)
194   /// weakVar           | 0 (known)           | weakVar (VarDecl)
195   /// self->weakIvar    | self (VarDecl)      | weakIvar (ObjCIvarDecl)
196   ///
197   /// Objects are identified with only two Decls to make it reasonably fast to
198   /// compare them.
199   class WeakObjectProfileTy {
200     /// The base object decl, as described in the class documentation.
201     ///
202     /// The extra flag is "true" if the Base and Property are enough to uniquely
203     /// identify the object in memory.
204     ///
205     /// \sa isExactProfile()
206     typedef llvm::PointerIntPair<const NamedDecl *, 1, bool> BaseInfoTy;
207     BaseInfoTy Base;
208 
209     /// The "property" decl, as described in the class documentation.
210     ///
211     /// Note that this may not actually be an ObjCPropertyDecl, e.g. in the
212     /// case of "implicit" properties (regular methods accessed via dot syntax).
213     const NamedDecl *Property;
214 
215     /// Used to find the proper base profile for a given base expression.
216     static BaseInfoTy getBaseInfo(const Expr *BaseE);
217 
218     inline WeakObjectProfileTy();
219     static inline WeakObjectProfileTy getSentinel();
220 
221   public:
222     WeakObjectProfileTy(const ObjCPropertyRefExpr *RE);
223     WeakObjectProfileTy(const Expr *Base, const ObjCPropertyDecl *Property);
224     WeakObjectProfileTy(const DeclRefExpr *RE);
225     WeakObjectProfileTy(const ObjCIvarRefExpr *RE);
226 
getBase()227     const NamedDecl *getBase() const { return Base.getPointer(); }
getProperty()228     const NamedDecl *getProperty() const { return Property; }
229 
230     /// Returns true if the object base specifies a known object in memory,
231     /// rather than, say, an instance variable or property of another object.
232     ///
233     /// Note that this ignores the effects of aliasing; that is, \c foo.bar is
234     /// considered an exact profile if \c foo is a local variable, even if
235     /// another variable \c foo2 refers to the same object as \c foo.
236     ///
237     /// For increased precision, accesses with base variables that are
238     /// properties or ivars of 'self' (e.g. self.prop1.prop2) are considered to
239     /// be exact, though this is not true for arbitrary variables
240     /// (foo.prop1.prop2).
isExactProfile()241     bool isExactProfile() const {
242       return Base.getInt();
243     }
244 
245     bool operator==(const WeakObjectProfileTy &Other) const {
246       return Base == Other.Base && Property == Other.Property;
247     }
248 
249     // For use in DenseMap.
250     // We can't specialize the usual llvm::DenseMapInfo at the end of the file
251     // because by that point the DenseMap in FunctionScopeInfo has already been
252     // instantiated.
253     class DenseMapInfo {
254     public:
getEmptyKey()255       static inline WeakObjectProfileTy getEmptyKey() {
256         return WeakObjectProfileTy();
257       }
getTombstoneKey()258       static inline WeakObjectProfileTy getTombstoneKey() {
259         return WeakObjectProfileTy::getSentinel();
260       }
261 
getHashValue(const WeakObjectProfileTy & Val)262       static unsigned getHashValue(const WeakObjectProfileTy &Val) {
263         typedef std::pair<BaseInfoTy, const NamedDecl *> Pair;
264         return llvm::DenseMapInfo<Pair>::getHashValue(Pair(Val.Base,
265                                                            Val.Property));
266       }
267 
isEqual(const WeakObjectProfileTy & LHS,const WeakObjectProfileTy & RHS)268       static bool isEqual(const WeakObjectProfileTy &LHS,
269                           const WeakObjectProfileTy &RHS) {
270         return LHS == RHS;
271       }
272     };
273   };
274 
275   /// Represents a single use of a weak object.
276   ///
277   /// Stores both the expression and whether the access is potentially unsafe
278   /// (i.e. it could potentially be warned about).
279   ///
280   /// Part of the implementation of -Wrepeated-use-of-weak.
281   class WeakUseTy {
282     llvm::PointerIntPair<const Expr *, 1, bool> Rep;
283   public:
WeakUseTy(const Expr * Use,bool IsRead)284     WeakUseTy(const Expr *Use, bool IsRead) : Rep(Use, IsRead) {}
285 
getUseExpr()286     const Expr *getUseExpr() const { return Rep.getPointer(); }
isUnsafe()287     bool isUnsafe() const { return Rep.getInt(); }
markSafe()288     void markSafe() { Rep.setInt(false); }
289 
290     bool operator==(const WeakUseTy &Other) const {
291       return Rep == Other.Rep;
292     }
293   };
294 
295   /// Used to collect uses of a particular weak object in a function body.
296   ///
297   /// Part of the implementation of -Wrepeated-use-of-weak.
298   typedef SmallVector<WeakUseTy, 4> WeakUseVector;
299 
300   /// Used to collect all uses of weak objects in a function body.
301   ///
302   /// Part of the implementation of -Wrepeated-use-of-weak.
303   typedef llvm::SmallDenseMap<WeakObjectProfileTy, WeakUseVector, 8,
304                               WeakObjectProfileTy::DenseMapInfo>
305           WeakObjectUseMap;
306 
307 private:
308   /// Used to collect all uses of weak objects in this function body.
309   ///
310   /// Part of the implementation of -Wrepeated-use-of-weak.
311   WeakObjectUseMap WeakObjectUses;
312 
313 protected:
314   FunctionScopeInfo(const FunctionScopeInfo&) = default;
315 
316 public:
317   /// Record that a weak object was accessed.
318   ///
319   /// Part of the implementation of -Wrepeated-use-of-weak.
320   template <typename ExprT>
321   inline void recordUseOfWeak(const ExprT *E, bool IsRead = true);
322 
323   void recordUseOfWeak(const ObjCMessageExpr *Msg,
324                        const ObjCPropertyDecl *Prop);
325 
326   /// Record that a given expression is a "safe" access of a weak object (e.g.
327   /// assigning it to a strong variable.)
328   ///
329   /// Part of the implementation of -Wrepeated-use-of-weak.
330   void markSafeWeakUse(const Expr *E);
331 
getWeakObjectUses()332   const WeakObjectUseMap &getWeakObjectUses() const {
333     return WeakObjectUses;
334   }
335 
setHasBranchIntoScope()336   void setHasBranchIntoScope() {
337     HasBranchIntoScope = true;
338   }
339 
setHasBranchProtectedScope()340   void setHasBranchProtectedScope() {
341     HasBranchProtectedScope = true;
342   }
343 
setHasIndirectGoto()344   void setHasIndirectGoto() {
345     HasIndirectGoto = true;
346   }
347 
setHasDroppedStmt()348   void setHasDroppedStmt() {
349     HasDroppedStmt = true;
350   }
351 
setHasOMPDeclareReductionCombiner()352   void setHasOMPDeclareReductionCombiner() {
353     HasOMPDeclareReductionCombiner = true;
354   }
355 
setHasFallthroughStmt()356   void setHasFallthroughStmt() {
357     HasFallthroughStmt = true;
358   }
359 
setHasCXXTry(SourceLocation TryLoc)360   void setHasCXXTry(SourceLocation TryLoc) {
361     setHasBranchProtectedScope();
362     FirstCXXTryLoc = TryLoc;
363   }
364 
setHasSEHTry(SourceLocation TryLoc)365   void setHasSEHTry(SourceLocation TryLoc) {
366     setHasBranchProtectedScope();
367     FirstSEHTryLoc = TryLoc;
368   }
369 
NeedsScopeChecking()370   bool NeedsScopeChecking() const {
371     return !HasDroppedStmt &&
372         (HasIndirectGoto ||
373           (HasBranchProtectedScope && HasBranchIntoScope));
374   }
375 
FunctionScopeInfo(DiagnosticsEngine & Diag)376   FunctionScopeInfo(DiagnosticsEngine &Diag)
377     : Kind(SK_Function),
378       HasBranchProtectedScope(false),
379       HasBranchIntoScope(false),
380       HasIndirectGoto(false),
381       HasDroppedStmt(false),
382       HasOMPDeclareReductionCombiner(false),
383       HasFallthroughStmt(false),
384       ObjCShouldCallSuper(false),
385       ObjCIsDesignatedInit(false),
386       ObjCWarnForNoDesignatedInitChain(false),
387       ObjCIsSecondaryInit(false),
388       ObjCWarnForNoInitDelegation(false),
389       ErrorTrap(Diag) { }
390 
391   virtual ~FunctionScopeInfo();
392 
393   /// \brief Clear out the information in this function scope, making it
394   /// suitable for reuse.
395   void Clear();
396 };
397 
398 class CapturingScopeInfo : public FunctionScopeInfo {
399 protected:
400   CapturingScopeInfo(const CapturingScopeInfo&) = default;
401 
402 public:
403   enum ImplicitCaptureStyle {
404     ImpCap_None, ImpCap_LambdaByval, ImpCap_LambdaByref, ImpCap_Block,
405     ImpCap_CapturedRegion
406   };
407 
408   ImplicitCaptureStyle ImpCaptureStyle;
409 
410   class Capture {
411     // There are three categories of capture: capturing 'this', capturing
412     // local variables, and C++1y initialized captures (which can have an
413     // arbitrary initializer, and don't really capture in the traditional
414     // sense at all).
415     //
416     // There are three ways to capture a local variable:
417     //  - capture by copy in the C++11 sense,
418     //  - capture by reference in the C++11 sense, and
419     //  - __block capture.
420     // Lambdas explicitly specify capture by copy or capture by reference.
421     // For blocks, __block capture applies to variables with that annotation,
422     // variables of reference type are captured by reference, and other
423     // variables are captured by copy.
424     enum CaptureKind {
425       Cap_ByCopy, Cap_ByRef, Cap_Block, Cap_VLA
426     };
427     enum {
428       IsNestedCapture = 0x1,
429       IsThisCaptured = 0x2
430     };
431     /// The variable being captured (if we are not capturing 'this') and whether
432     /// this is a nested capture, and whether we are capturing 'this'
433     llvm::PointerIntPair<VarDecl*, 2> VarAndNestedAndThis;
434     /// Expression to initialize a field of the given type, and the kind of
435     /// capture (if this is a capture and not an init-capture). The expression
436     /// is only required if we are capturing ByVal and the variable's type has
437     /// a non-trivial copy constructor.
438     llvm::PointerIntPair<void *, 2, CaptureKind> InitExprAndCaptureKind;
439 
440     /// \brief The source location at which the first capture occurred.
441     SourceLocation Loc;
442 
443     /// \brief The location of the ellipsis that expands a parameter pack.
444     SourceLocation EllipsisLoc;
445 
446     /// \brief The type as it was captured, which is in effect the type of the
447     /// non-static data member that would hold the capture.
448     QualType CaptureType;
449 
450   public:
Capture(VarDecl * Var,bool Block,bool ByRef,bool IsNested,SourceLocation Loc,SourceLocation EllipsisLoc,QualType CaptureType,Expr * Cpy)451     Capture(VarDecl *Var, bool Block, bool ByRef, bool IsNested,
452             SourceLocation Loc, SourceLocation EllipsisLoc,
453             QualType CaptureType, Expr *Cpy)
454         : VarAndNestedAndThis(Var, IsNested ? IsNestedCapture : 0),
455           InitExprAndCaptureKind(
456               Cpy, !Var ? Cap_VLA : Block ? Cap_Block : ByRef ? Cap_ByRef
457                                                               : Cap_ByCopy),
458           Loc(Loc), EllipsisLoc(EllipsisLoc), CaptureType(CaptureType) {}
459 
460     enum IsThisCapture { ThisCapture };
Capture(IsThisCapture,bool IsNested,SourceLocation Loc,QualType CaptureType,Expr * Cpy,const bool ByCopy)461     Capture(IsThisCapture, bool IsNested, SourceLocation Loc,
462             QualType CaptureType, Expr *Cpy, const bool ByCopy)
463         : VarAndNestedAndThis(
464               nullptr, (IsThisCaptured | (IsNested ? IsNestedCapture : 0))),
465           InitExprAndCaptureKind(Cpy, ByCopy ? Cap_ByCopy : Cap_ByRef),
466           Loc(Loc), EllipsisLoc(), CaptureType(CaptureType) {}
467 
isThisCapture()468     bool isThisCapture() const {
469       return VarAndNestedAndThis.getInt() & IsThisCaptured;
470     }
isVariableCapture()471     bool isVariableCapture() const {
472       return !isThisCapture() && !isVLATypeCapture();
473     }
isCopyCapture()474     bool isCopyCapture() const {
475       return InitExprAndCaptureKind.getInt() == Cap_ByCopy;
476     }
isReferenceCapture()477     bool isReferenceCapture() const {
478       return InitExprAndCaptureKind.getInt() == Cap_ByRef;
479     }
isBlockCapture()480     bool isBlockCapture() const {
481       return InitExprAndCaptureKind.getInt() == Cap_Block;
482     }
isVLATypeCapture()483     bool isVLATypeCapture() const {
484       return InitExprAndCaptureKind.getInt() == Cap_VLA;
485     }
isNested()486     bool isNested() const {
487       return VarAndNestedAndThis.getInt() & IsNestedCapture;
488     }
489 
getVariable()490     VarDecl *getVariable() const {
491       return VarAndNestedAndThis.getPointer();
492     }
493 
494     /// \brief Retrieve the location at which this variable was captured.
getLocation()495     SourceLocation getLocation() const { return Loc; }
496 
497     /// \brief Retrieve the source location of the ellipsis, whose presence
498     /// indicates that the capture is a pack expansion.
getEllipsisLoc()499     SourceLocation getEllipsisLoc() const { return EllipsisLoc; }
500 
501     /// \brief Retrieve the capture type for this capture, which is effectively
502     /// the type of the non-static data member in the lambda/block structure
503     /// that would store this capture.
getCaptureType()504     QualType getCaptureType() const {
505       assert(!isThisCapture());
506       return CaptureType;
507     }
508 
getInitExpr()509     Expr *getInitExpr() const {
510       assert(!isVLATypeCapture() && "no init expression for type capture");
511       return static_cast<Expr *>(InitExprAndCaptureKind.getPointer());
512     }
513   };
514 
CapturingScopeInfo(DiagnosticsEngine & Diag,ImplicitCaptureStyle Style)515   CapturingScopeInfo(DiagnosticsEngine &Diag, ImplicitCaptureStyle Style)
516     : FunctionScopeInfo(Diag), ImpCaptureStyle(Style), CXXThisCaptureIndex(0),
517       HasImplicitReturnType(false)
518      {}
519 
520   /// CaptureMap - A map of captured variables to (index+1) into Captures.
521   llvm::DenseMap<VarDecl*, unsigned> CaptureMap;
522 
523   /// CXXThisCaptureIndex - The (index+1) of the capture of 'this';
524   /// zero if 'this' is not captured.
525   unsigned CXXThisCaptureIndex;
526 
527   /// Captures - The captures.
528   SmallVector<Capture, 4> Captures;
529 
530   /// \brief - Whether the target type of return statements in this context
531   /// is deduced (e.g. a lambda or block with omitted return type).
532   bool HasImplicitReturnType;
533 
534   /// ReturnType - The target type of return statements in this context,
535   /// or null if unknown.
536   QualType ReturnType;
537 
addCapture(VarDecl * Var,bool isBlock,bool isByref,bool isNested,SourceLocation Loc,SourceLocation EllipsisLoc,QualType CaptureType,Expr * Cpy)538   void addCapture(VarDecl *Var, bool isBlock, bool isByref, bool isNested,
539                   SourceLocation Loc, SourceLocation EllipsisLoc,
540                   QualType CaptureType, Expr *Cpy) {
541     Captures.push_back(Capture(Var, isBlock, isByref, isNested, Loc,
542                                EllipsisLoc, CaptureType, Cpy));
543     CaptureMap[Var] = Captures.size();
544   }
545 
addVLATypeCapture(SourceLocation Loc,QualType CaptureType)546   void addVLATypeCapture(SourceLocation Loc, QualType CaptureType) {
547     Captures.push_back(Capture(/*Var*/ nullptr, /*isBlock*/ false,
548                                /*isByref*/ false, /*isNested*/ false, Loc,
549                                /*EllipsisLoc*/ SourceLocation(), CaptureType,
550                                /*Cpy*/ nullptr));
551   }
552 
553   // Note, we do not need to add the type of 'this' since that is always
554   // retrievable from Sema::getCurrentThisType - and is also encoded within the
555   // type of the corresponding FieldDecl.
556   void addThisCapture(bool isNested, SourceLocation Loc,
557                       Expr *Cpy, bool ByCopy);
558 
559   /// \brief Determine whether the C++ 'this' is captured.
isCXXThisCaptured()560   bool isCXXThisCaptured() const { return CXXThisCaptureIndex != 0; }
561 
562   /// \brief Retrieve the capture of C++ 'this', if it has been captured.
getCXXThisCapture()563   Capture &getCXXThisCapture() {
564     assert(isCXXThisCaptured() && "this has not been captured");
565     return Captures[CXXThisCaptureIndex - 1];
566   }
567 
568   /// \brief Determine whether the given variable has been captured.
isCaptured(VarDecl * Var)569   bool isCaptured(VarDecl *Var) const {
570     return CaptureMap.count(Var);
571   }
572 
573   /// \brief Determine whether the given variable-array type has been captured.
574   bool isVLATypeCaptured(const VariableArrayType *VAT) const;
575 
576   /// \brief Retrieve the capture of the given variable, if it has been
577   /// captured already.
getCapture(VarDecl * Var)578   Capture &getCapture(VarDecl *Var) {
579     assert(isCaptured(Var) && "Variable has not been captured");
580     return Captures[CaptureMap[Var] - 1];
581   }
582 
getCapture(VarDecl * Var)583   const Capture &getCapture(VarDecl *Var) const {
584     llvm::DenseMap<VarDecl*, unsigned>::const_iterator Known
585       = CaptureMap.find(Var);
586     assert(Known != CaptureMap.end() && "Variable has not been captured");
587     return Captures[Known->second - 1];
588   }
589 
classof(const FunctionScopeInfo * FSI)590   static bool classof(const FunctionScopeInfo *FSI) {
591     return FSI->Kind == SK_Block || FSI->Kind == SK_Lambda
592                                  || FSI->Kind == SK_CapturedRegion;
593   }
594 };
595 
596 /// \brief Retains information about a block that is currently being parsed.
597 class BlockScopeInfo final : public CapturingScopeInfo {
598 public:
599   BlockDecl *TheDecl;
600 
601   /// TheScope - This is the scope for the block itself, which contains
602   /// arguments etc.
603   Scope *TheScope;
604 
605   /// BlockType - The function type of the block, if one was given.
606   /// Its return type may be BuiltinType::Dependent.
607   QualType FunctionType;
608 
BlockScopeInfo(DiagnosticsEngine & Diag,Scope * BlockScope,BlockDecl * Block)609   BlockScopeInfo(DiagnosticsEngine &Diag, Scope *BlockScope, BlockDecl *Block)
610     : CapturingScopeInfo(Diag, ImpCap_Block), TheDecl(Block),
611       TheScope(BlockScope)
612   {
613     Kind = SK_Block;
614   }
615 
616   ~BlockScopeInfo() override;
617 
classof(const FunctionScopeInfo * FSI)618   static bool classof(const FunctionScopeInfo *FSI) {
619     return FSI->Kind == SK_Block;
620   }
621 };
622 
623 /// \brief Retains information about a captured region.
624 class CapturedRegionScopeInfo final : public CapturingScopeInfo {
625 public:
626   /// \brief The CapturedDecl for this statement.
627   CapturedDecl *TheCapturedDecl;
628   /// \brief The captured record type.
629   RecordDecl *TheRecordDecl;
630   /// \brief This is the enclosing scope of the captured region.
631   Scope *TheScope;
632   /// \brief The implicit parameter for the captured variables.
633   ImplicitParamDecl *ContextParam;
634   /// \brief The kind of captured region.
635   unsigned short CapRegionKind;
636   unsigned short OpenMPLevel;
637 
CapturedRegionScopeInfo(DiagnosticsEngine & Diag,Scope * S,CapturedDecl * CD,RecordDecl * RD,ImplicitParamDecl * Context,CapturedRegionKind K,unsigned OpenMPLevel)638   CapturedRegionScopeInfo(DiagnosticsEngine &Diag, Scope *S, CapturedDecl *CD,
639                           RecordDecl *RD, ImplicitParamDecl *Context,
640                           CapturedRegionKind K, unsigned OpenMPLevel)
641     : CapturingScopeInfo(Diag, ImpCap_CapturedRegion),
642       TheCapturedDecl(CD), TheRecordDecl(RD), TheScope(S),
643       ContextParam(Context), CapRegionKind(K), OpenMPLevel(OpenMPLevel)
644   {
645     Kind = SK_CapturedRegion;
646   }
647 
648   ~CapturedRegionScopeInfo() override;
649 
650   /// \brief A descriptive name for the kind of captured region this is.
getRegionName()651   StringRef getRegionName() const {
652     switch (CapRegionKind) {
653     case CR_Default:
654       return "default captured statement";
655     case CR_OpenMP:
656       return "OpenMP region";
657     }
658     llvm_unreachable("Invalid captured region kind!");
659   }
660 
classof(const FunctionScopeInfo * FSI)661   static bool classof(const FunctionScopeInfo *FSI) {
662     return FSI->Kind == SK_CapturedRegion;
663   }
664 };
665 
666 class LambdaScopeInfo final : public CapturingScopeInfo {
667 public:
668   /// \brief The class that describes the lambda.
669   CXXRecordDecl *Lambda;
670 
671   /// \brief The lambda's compiler-generated \c operator().
672   CXXMethodDecl *CallOperator;
673 
674   /// \brief Source range covering the lambda introducer [...].
675   SourceRange IntroducerRange;
676 
677   /// \brief Source location of the '&' or '=' specifying the default capture
678   /// type, if any.
679   SourceLocation CaptureDefaultLoc;
680 
681   /// \brief The number of captures in the \c Captures list that are
682   /// explicit captures.
683   unsigned NumExplicitCaptures;
684 
685   /// \brief Whether this is a mutable lambda.
686   bool Mutable;
687 
688   /// \brief Whether the (empty) parameter list is explicit.
689   bool ExplicitParams;
690 
691   /// \brief Whether any of the capture expressions requires cleanups.
692   CleanupInfo Cleanup;
693 
694   /// \brief Whether the lambda contains an unexpanded parameter pack.
695   bool ContainsUnexpandedParameterPack;
696 
697   /// \brief If this is a generic lambda, use this as the depth of
698   /// each 'auto' parameter, during initial AST construction.
699   unsigned AutoTemplateParameterDepth;
700 
701   /// \brief Store the list of the auto parameters for a generic lambda.
702   /// If this is a generic lambda, store the list of the auto
703   /// parameters converted into TemplateTypeParmDecls into a vector
704   /// that can be used to construct the generic lambda's template
705   /// parameter list, during initial AST construction.
706   SmallVector<TemplateTypeParmDecl*, 4> AutoTemplateParams;
707 
708   /// If this is a generic lambda, and the template parameter
709   /// list has been created (from the AutoTemplateParams) then
710   /// store a reference to it (cache it to avoid reconstructing it).
711   TemplateParameterList *GLTemplateParameterList;
712 
713   /// \brief Contains all variable-referring-expressions (i.e. DeclRefExprs
714   ///  or MemberExprs) that refer to local variables in a generic lambda
715   ///  or a lambda in a potentially-evaluated-if-used context.
716   ///
717   ///  Potentially capturable variables of a nested lambda that might need
718   ///   to be captured by the lambda are housed here.
719   ///  This is specifically useful for generic lambdas or
720   ///  lambdas within a a potentially evaluated-if-used context.
721   ///  If an enclosing variable is named in an expression of a lambda nested
722   ///  within a generic lambda, we don't always know know whether the variable
723   ///  will truly be odr-used (i.e. need to be captured) by that nested lambda,
724   ///  until its instantiation. But we still need to capture it in the
725   ///  enclosing lambda if all intervening lambdas can capture the variable.
726 
727   llvm::SmallVector<Expr*, 4> PotentiallyCapturingExprs;
728 
729   /// \brief Contains all variable-referring-expressions that refer
730   ///  to local variables that are usable as constant expressions and
731   ///  do not involve an odr-use (they may still need to be captured
732   ///  if the enclosing full-expression is instantiation dependent).
733   llvm::SmallSet<Expr*, 8> NonODRUsedCapturingExprs;
734 
735   SourceLocation PotentialThisCaptureLocation;
736 
LambdaScopeInfo(DiagnosticsEngine & Diag)737   LambdaScopeInfo(DiagnosticsEngine &Diag)
738     : CapturingScopeInfo(Diag, ImpCap_None), Lambda(nullptr),
739       CallOperator(nullptr), NumExplicitCaptures(0), Mutable(false),
740       ExplicitParams(false), Cleanup{},
741       ContainsUnexpandedParameterPack(false), AutoTemplateParameterDepth(0),
742       GLTemplateParameterList(nullptr) {
743     Kind = SK_Lambda;
744   }
745 
746   /// \brief Note when all explicit captures have been added.
finishedExplicitCaptures()747   void finishedExplicitCaptures() {
748     NumExplicitCaptures = Captures.size();
749   }
750 
classof(const FunctionScopeInfo * FSI)751   static bool classof(const FunctionScopeInfo *FSI) {
752     return FSI->Kind == SK_Lambda;
753   }
754 
755   ///
756   /// \brief Add a variable that might potentially be captured by the
757   /// lambda and therefore the enclosing lambdas.
758   ///
759   /// This is also used by enclosing lambda's to speculatively capture
760   /// variables that nested lambda's - depending on their enclosing
761   /// specialization - might need to capture.
762   /// Consider:
763   /// void f(int, int); <-- don't capture
764   /// void f(const int&, double); <-- capture
765   /// void foo() {
766   ///   const int x = 10;
767   ///   auto L = [=](auto a) { // capture 'x'
768   ///      return [=](auto b) {
769   ///        f(x, a);  // we may or may not need to capture 'x'
770   ///      };
771   ///   };
772   /// }
addPotentialCapture(Expr * VarExpr)773   void addPotentialCapture(Expr *VarExpr) {
774     assert(isa<DeclRefExpr>(VarExpr) || isa<MemberExpr>(VarExpr));
775     PotentiallyCapturingExprs.push_back(VarExpr);
776   }
777 
addPotentialThisCapture(SourceLocation Loc)778   void addPotentialThisCapture(SourceLocation Loc) {
779     PotentialThisCaptureLocation = Loc;
780   }
hasPotentialThisCapture()781   bool hasPotentialThisCapture() const {
782     return PotentialThisCaptureLocation.isValid();
783   }
784 
785   /// \brief Mark a variable's reference in a lambda as non-odr using.
786   ///
787   /// For generic lambdas, if a variable is named in a potentially evaluated
788   /// expression, where the enclosing full expression is dependent then we
789   /// must capture the variable (given a default capture).
790   /// This is accomplished by recording all references to variables
791   /// (DeclRefExprs or MemberExprs) within said nested lambda in its array of
792   /// PotentialCaptures. All such variables have to be captured by that lambda,
793   /// except for as described below.
794   /// If that variable is usable as a constant expression and is named in a
795   /// manner that does not involve its odr-use (e.g. undergoes
796   /// lvalue-to-rvalue conversion, or discarded) record that it is so. Upon the
797   /// act of analyzing the enclosing full expression (ActOnFinishFullExpr)
798   /// if we can determine that the full expression is not instantiation-
799   /// dependent, then we can entirely avoid its capture.
800   ///
801   ///   const int n = 0;
802   ///   [&] (auto x) {
803   ///     (void)+n + x;
804   ///   };
805   /// Interestingly, this strategy would involve a capture of n, even though
806   /// it's obviously not odr-used here, because the full-expression is
807   /// instantiation-dependent.  It could be useful to avoid capturing such
808   /// variables, even when they are referred to in an instantiation-dependent
809   /// expression, if we can unambiguously determine that they shall never be
810   /// odr-used.  This would involve removal of the variable-referring-expression
811   /// from the array of PotentialCaptures during the lvalue-to-rvalue
812   /// conversions.  But per the working draft N3797, (post-chicago 2013) we must
813   /// capture such variables.
814   /// Before anyone is tempted to implement a strategy for not-capturing 'n',
815   /// consider the insightful warning in:
816   ///    /cfe-commits/Week-of-Mon-20131104/092596.html
817   /// "The problem is that the set of captures for a lambda is part of the ABI
818   ///  (since lambda layout can be made visible through inline functions and the
819   ///  like), and there are no guarantees as to which cases we'll manage to build
820   ///  an lvalue-to-rvalue conversion in, when parsing a template -- some
821   ///  seemingly harmless change elsewhere in Sema could cause us to start or stop
822   ///  building such a node. So we need a rule that anyone can implement and get
823   ///  exactly the same result".
824   ///
markVariableExprAsNonODRUsed(Expr * CapturingVarExpr)825   void markVariableExprAsNonODRUsed(Expr *CapturingVarExpr) {
826     assert(isa<DeclRefExpr>(CapturingVarExpr)
827         || isa<MemberExpr>(CapturingVarExpr));
828     NonODRUsedCapturingExprs.insert(CapturingVarExpr);
829   }
isVariableExprMarkedAsNonODRUsed(Expr * CapturingVarExpr)830   bool isVariableExprMarkedAsNonODRUsed(Expr *CapturingVarExpr) const {
831     assert(isa<DeclRefExpr>(CapturingVarExpr)
832       || isa<MemberExpr>(CapturingVarExpr));
833     return NonODRUsedCapturingExprs.count(CapturingVarExpr);
834   }
removePotentialCapture(Expr * E)835   void removePotentialCapture(Expr *E) {
836     PotentiallyCapturingExprs.erase(
837         std::remove(PotentiallyCapturingExprs.begin(),
838             PotentiallyCapturingExprs.end(), E),
839         PotentiallyCapturingExprs.end());
840   }
clearPotentialCaptures()841   void clearPotentialCaptures() {
842     PotentiallyCapturingExprs.clear();
843     PotentialThisCaptureLocation = SourceLocation();
844   }
getNumPotentialVariableCaptures()845   unsigned getNumPotentialVariableCaptures() const {
846     return PotentiallyCapturingExprs.size();
847   }
848 
hasPotentialCaptures()849   bool hasPotentialCaptures() const {
850     return getNumPotentialVariableCaptures() ||
851                                   PotentialThisCaptureLocation.isValid();
852   }
853 
854   // When passed the index, returns the VarDecl and Expr associated
855   // with the index.
856   void getPotentialVariableCapture(unsigned Idx, VarDecl *&VD, Expr *&E) const;
857 };
858 
WeakObjectProfileTy()859 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy()
860   : Base(nullptr, false), Property(nullptr) {}
861 
862 FunctionScopeInfo::WeakObjectProfileTy
getSentinel()863 FunctionScopeInfo::WeakObjectProfileTy::getSentinel() {
864   FunctionScopeInfo::WeakObjectProfileTy Result;
865   Result.Base.setInt(true);
866   return Result;
867 }
868 
869 template <typename ExprT>
recordUseOfWeak(const ExprT * E,bool IsRead)870 void FunctionScopeInfo::recordUseOfWeak(const ExprT *E, bool IsRead) {
871   assert(E);
872   WeakUseVector &Uses = WeakObjectUses[WeakObjectProfileTy(E)];
873   Uses.push_back(WeakUseTy(E, IsRead));
874 }
875 
876 inline void
addThisCapture(bool isNested,SourceLocation Loc,Expr * Cpy,const bool ByCopy)877 CapturingScopeInfo::addThisCapture(bool isNested, SourceLocation Loc,
878                                    Expr *Cpy,
879                                    const bool ByCopy) {
880   Captures.push_back(Capture(Capture::ThisCapture, isNested, Loc, QualType(),
881                              Cpy, ByCopy));
882   CXXThisCaptureIndex = Captures.size();
883 }
884 
885 } // end namespace sema
886 } // end namespace clang
887 
888 #endif
889