1 //===- ScopeInfo.h - Information about a semantic context -------*- C++ -*-===//
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 defines FunctionScopeInfo and its subclasses, which contain
10 // information about a single function, block, lambda, or method body.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_SEMA_SCOPEINFO_H
15 #define LLVM_CLANG_SEMA_SCOPEINFO_H
16 
17 #include "clang/AST/Expr.h"
18 #include "clang/AST/ExprCXX.h"
19 #include "clang/AST/Type.h"
20 #include "clang/Basic/CapturedStmt.h"
21 #include "clang/Basic/LLVM.h"
22 #include "clang/Basic/PartialDiagnostic.h"
23 #include "clang/Basic/SourceLocation.h"
24 #include "clang/Sema/CleanupInfo.h"
25 #include "clang/Sema/DeclSpec.h"
26 #include "llvm/ADT/DenseMap.h"
27 #include "llvm/ADT/DenseMapInfo.h"
28 #include "llvm/ADT/MapVector.h"
29 #include "llvm/ADT/PointerIntPair.h"
30 #include "llvm/ADT/SmallPtrSet.h"
31 #include "llvm/ADT/SmallSet.h"
32 #include "llvm/ADT/SmallVector.h"
33 #include "llvm/ADT/StringRef.h"
34 #include "llvm/ADT/StringSwitch.h"
35 #include "llvm/ADT/TinyPtrVector.h"
36 #include "llvm/Support/Casting.h"
37 #include "llvm/Support/ErrorHandling.h"
38 #include <algorithm>
39 #include <cassert>
40 #include <utility>
41 
42 namespace clang {
43 
44 class BlockDecl;
45 class CapturedDecl;
46 class CXXMethodDecl;
47 class CXXRecordDecl;
48 class ImplicitParamDecl;
49 class NamedDecl;
50 class ObjCIvarRefExpr;
51 class ObjCMessageExpr;
52 class ObjCPropertyDecl;
53 class ObjCPropertyRefExpr;
54 class ParmVarDecl;
55 class RecordDecl;
56 class ReturnStmt;
57 class Scope;
58 class Stmt;
59 class SwitchStmt;
60 class TemplateParameterList;
61 class VarDecl;
62 
63 namespace sema {
64 
65 /// Contains information about the compound statement currently being
66 /// parsed.
67 class CompoundScopeInfo {
68 public:
69   /// Whether this compound stamement contains `for' or `while' loops
70   /// with empty bodies.
71   bool HasEmptyLoopBodies = false;
72 
73   /// Whether this compound statement corresponds to a GNU statement
74   /// expression.
75   bool IsStmtExpr;
76 
77   /// FP options at the beginning of the compound statement, prior to
78   /// any pragma.
79   FPOptions InitialFPFeatures;
80 
CompoundScopeInfo(bool IsStmtExpr,FPOptions FPO)81   CompoundScopeInfo(bool IsStmtExpr, FPOptions FPO)
82       : IsStmtExpr(IsStmtExpr), InitialFPFeatures(FPO) {}
83 
setHasEmptyLoopBodies()84   void setHasEmptyLoopBodies() {
85     HasEmptyLoopBodies = true;
86   }
87 };
88 
89 class PossiblyUnreachableDiag {
90 public:
91   PartialDiagnostic PD;
92   SourceLocation Loc;
93   llvm::TinyPtrVector<const Stmt*> Stmts;
94 
PossiblyUnreachableDiag(const PartialDiagnostic & PD,SourceLocation Loc,ArrayRef<const Stmt * > Stmts)95   PossiblyUnreachableDiag(const PartialDiagnostic &PD, SourceLocation Loc,
96                           ArrayRef<const Stmt *> Stmts)
97       : PD(PD), Loc(Loc), Stmts(Stmts) {}
98 };
99 
100 /// Retains information about a function, method, or block that is
101 /// currently being parsed.
102 class FunctionScopeInfo {
103 protected:
104   enum ScopeKind {
105     SK_Function,
106     SK_Block,
107     SK_Lambda,
108     SK_CapturedRegion
109   };
110 
111 public:
112   /// What kind of scope we are describing.
113   ScopeKind Kind : 3;
114 
115   /// Whether this function contains a VLA, \@try, try, C++
116   /// initializer, or anything else that can't be jumped past.
117   bool HasBranchProtectedScope : 1;
118 
119   /// Whether this function contains any switches or direct gotos.
120   bool HasBranchIntoScope : 1;
121 
122   /// Whether this function contains any indirect gotos.
123   bool HasIndirectGoto : 1;
124 
125   /// Whether this function contains any statement marked with
126   /// \c [[clang::musttail]].
127   bool HasMustTail : 1;
128 
129   /// Whether a statement was dropped because it was invalid.
130   bool HasDroppedStmt : 1;
131 
132   /// True if current scope is for OpenMP declare reduction combiner.
133   bool HasOMPDeclareReductionCombiner : 1;
134 
135   /// Whether there is a fallthrough statement in this function.
136   bool HasFallthroughStmt : 1;
137 
138   /// Whether this function uses constrained floating point intrinsics
139   bool UsesFPIntrin : 1;
140 
141   /// Whether we make reference to a declaration that could be
142   /// unavailable.
143   bool HasPotentialAvailabilityViolations : 1;
144 
145   /// A flag that is set when parsing a method that must call super's
146   /// implementation, such as \c -dealloc, \c -finalize, or any method marked
147   /// with \c __attribute__((objc_requires_super)).
148   bool ObjCShouldCallSuper : 1;
149 
150   /// True when this is a method marked as a designated initializer.
151   bool ObjCIsDesignatedInit : 1;
152 
153   /// This starts true for a method marked as designated initializer and will
154   /// be set to false if there is an invocation to a designated initializer of
155   /// the super class.
156   bool ObjCWarnForNoDesignatedInitChain : 1;
157 
158   /// True when this is an initializer method not marked as a designated
159   /// initializer within a class that has at least one initializer marked as a
160   /// designated initializer.
161   bool ObjCIsSecondaryInit : 1;
162 
163   /// This starts true for a secondary initializer method and will be set to
164   /// false if there is an invocation of an initializer on 'self'.
165   bool ObjCWarnForNoInitDelegation : 1;
166 
167   /// True only when this function has not already built, or attempted
168   /// to build, the initial and final coroutine suspend points
169   bool NeedsCoroutineSuspends : 1;
170 
171   /// An enumeration represeting the kind of the first coroutine statement
172   /// in the function. One of co_return, co_await, or co_yield.
173   unsigned char FirstCoroutineStmtKind : 2;
174 
175   /// First coroutine statement in the current function.
176   /// (ex co_return, co_await, co_yield)
177   SourceLocation FirstCoroutineStmtLoc;
178 
179   /// First 'return' statement in the current function.
180   SourceLocation FirstReturnLoc;
181 
182   /// First C++ 'try' or ObjC @try statement in the current function.
183   SourceLocation FirstCXXOrObjCTryLoc;
184   enum { TryLocIsCXX, TryLocIsObjC, Unknown } FirstTryType = Unknown;
185 
186   /// First SEH '__try' statement in the current function.
187   SourceLocation FirstSEHTryLoc;
188 
189 private:
190   /// Used to determine if errors occurred in this function or block.
191   DiagnosticErrorTrap ErrorTrap;
192 
193 public:
194   /// A SwitchStmt, along with a flag indicating if its list of case statements
195   /// is incomplete (because we dropped an invalid one while parsing).
196   using SwitchInfo = llvm::PointerIntPair<SwitchStmt*, 1, bool>;
197 
198   /// SwitchStack - This is the current set of active switch statements in the
199   /// block.
200   SmallVector<SwitchInfo, 8> SwitchStack;
201 
202   /// The list of return statements that occur within the function or
203   /// block, if there is any chance of applying the named return value
204   /// optimization, or if we need to infer a return type.
205   SmallVector<ReturnStmt*, 4> Returns;
206 
207   /// The promise object for this coroutine, if any.
208   VarDecl *CoroutinePromise = nullptr;
209 
210   /// A mapping between the coroutine function parameters that were moved
211   /// to the coroutine frame, and their move statements.
212   llvm::SmallMapVector<ParmVarDecl *, Stmt *, 4> CoroutineParameterMoves;
213 
214   /// The initial and final coroutine suspend points.
215   std::pair<Stmt *, Stmt *> CoroutineSuspends;
216 
217   /// The stack of currently active compound stamement scopes in the
218   /// function.
219   SmallVector<CompoundScopeInfo, 4> CompoundScopes;
220 
221   /// The set of blocks that are introduced in this function.
222   llvm::SmallPtrSet<const BlockDecl *, 1> Blocks;
223 
224   /// The set of __block variables that are introduced in this function.
225   llvm::TinyPtrVector<VarDecl *> ByrefBlockVars;
226 
227   /// A list of PartialDiagnostics created but delayed within the
228   /// current function scope.  These diagnostics are vetted for reachability
229   /// prior to being emitted.
230   SmallVector<PossiblyUnreachableDiag, 4> PossiblyUnreachableDiags;
231 
232   /// A list of parameters which have the nonnull attribute and are
233   /// modified in the function.
234   llvm::SmallPtrSet<const ParmVarDecl *, 8> ModifiedNonNullParams;
235 
236   /// The set of GNU address of label extension "&&label".
237   llvm::SmallVector<AddrLabelExpr *, 4> AddrLabels;
238 
239 public:
240   /// Represents a simple identification of a weak object.
241   ///
242   /// Part of the implementation of -Wrepeated-use-of-weak.
243   ///
244   /// This is used to determine if two weak accesses refer to the same object.
245   /// Here are some examples of how various accesses are "profiled":
246   ///
247   /// Access Expression |     "Base" Decl     |          "Property" Decl
248   /// :---------------: | :-----------------: | :------------------------------:
249   /// self.property     | self (VarDecl)      | property (ObjCPropertyDecl)
250   /// self.implicitProp | self (VarDecl)      | -implicitProp (ObjCMethodDecl)
251   /// self->ivar.prop   | ivar (ObjCIvarDecl) | prop (ObjCPropertyDecl)
252   /// cxxObj.obj.prop   | obj (FieldDecl)     | prop (ObjCPropertyDecl)
253   /// [self foo].prop   | 0 (unknown)         | prop (ObjCPropertyDecl)
254   /// self.prop1.prop2  | prop1 (ObjCPropertyDecl)    | prop2 (ObjCPropertyDecl)
255   /// MyClass.prop      | MyClass (ObjCInterfaceDecl) | -prop (ObjCMethodDecl)
256   /// MyClass.foo.prop  | +foo (ObjCMethodDecl)       | -prop (ObjCPropertyDecl)
257   /// weakVar           | 0 (known)           | weakVar (VarDecl)
258   /// self->weakIvar    | self (VarDecl)      | weakIvar (ObjCIvarDecl)
259   ///
260   /// Objects are identified with only two Decls to make it reasonably fast to
261   /// compare them.
262   class WeakObjectProfileTy {
263     /// The base object decl, as described in the class documentation.
264     ///
265     /// The extra flag is "true" if the Base and Property are enough to uniquely
266     /// identify the object in memory.
267     ///
268     /// \sa isExactProfile()
269     using BaseInfoTy = llvm::PointerIntPair<const NamedDecl *, 1, bool>;
270     BaseInfoTy Base;
271 
272     /// The "property" decl, as described in the class documentation.
273     ///
274     /// Note that this may not actually be an ObjCPropertyDecl, e.g. in the
275     /// case of "implicit" properties (regular methods accessed via dot syntax).
276     const NamedDecl *Property = nullptr;
277 
278     /// Used to find the proper base profile for a given base expression.
279     static BaseInfoTy getBaseInfo(const Expr *BaseE);
280 
281     inline WeakObjectProfileTy();
282     static inline WeakObjectProfileTy getSentinel();
283 
284   public:
285     WeakObjectProfileTy(const ObjCPropertyRefExpr *RE);
286     WeakObjectProfileTy(const Expr *Base, const ObjCPropertyDecl *Property);
287     WeakObjectProfileTy(const DeclRefExpr *RE);
288     WeakObjectProfileTy(const ObjCIvarRefExpr *RE);
289 
getBase()290     const NamedDecl *getBase() const { return Base.getPointer(); }
getProperty()291     const NamedDecl *getProperty() const { return Property; }
292 
293     /// Returns true if the object base specifies a known object in memory,
294     /// rather than, say, an instance variable or property of another object.
295     ///
296     /// Note that this ignores the effects of aliasing; that is, \c foo.bar is
297     /// considered an exact profile if \c foo is a local variable, even if
298     /// another variable \c foo2 refers to the same object as \c foo.
299     ///
300     /// For increased precision, accesses with base variables that are
301     /// properties or ivars of 'self' (e.g. self.prop1.prop2) are considered to
302     /// be exact, though this is not true for arbitrary variables
303     /// (foo.prop1.prop2).
isExactProfile()304     bool isExactProfile() const {
305       return Base.getInt();
306     }
307 
308     bool operator==(const WeakObjectProfileTy &Other) const {
309       return Base == Other.Base && Property == Other.Property;
310     }
311 
312     // For use in DenseMap.
313     // We can't specialize the usual llvm::DenseMapInfo at the end of the file
314     // because by that point the DenseMap in FunctionScopeInfo has already been
315     // instantiated.
316     class DenseMapInfo {
317     public:
getEmptyKey()318       static inline WeakObjectProfileTy getEmptyKey() {
319         return WeakObjectProfileTy();
320       }
321 
getTombstoneKey()322       static inline WeakObjectProfileTy getTombstoneKey() {
323         return WeakObjectProfileTy::getSentinel();
324       }
325 
getHashValue(const WeakObjectProfileTy & Val)326       static unsigned getHashValue(const WeakObjectProfileTy &Val) {
327         using Pair = std::pair<BaseInfoTy, const NamedDecl *>;
328 
329         return llvm::DenseMapInfo<Pair>::getHashValue(Pair(Val.Base,
330                                                            Val.Property));
331       }
332 
isEqual(const WeakObjectProfileTy & LHS,const WeakObjectProfileTy & RHS)333       static bool isEqual(const WeakObjectProfileTy &LHS,
334                           const WeakObjectProfileTy &RHS) {
335         return LHS == RHS;
336       }
337     };
338   };
339 
340   /// Represents a single use of a weak object.
341   ///
342   /// Stores both the expression and whether the access is potentially unsafe
343   /// (i.e. it could potentially be warned about).
344   ///
345   /// Part of the implementation of -Wrepeated-use-of-weak.
346   class WeakUseTy {
347     llvm::PointerIntPair<const Expr *, 1, bool> Rep;
348 
349   public:
WeakUseTy(const Expr * Use,bool IsRead)350     WeakUseTy(const Expr *Use, bool IsRead) : Rep(Use, IsRead) {}
351 
getUseExpr()352     const Expr *getUseExpr() const { return Rep.getPointer(); }
isUnsafe()353     bool isUnsafe() const { return Rep.getInt(); }
markSafe()354     void markSafe() { Rep.setInt(false); }
355 
356     bool operator==(const WeakUseTy &Other) const {
357       return Rep == Other.Rep;
358     }
359   };
360 
361   /// Used to collect uses of a particular weak object in a function body.
362   ///
363   /// Part of the implementation of -Wrepeated-use-of-weak.
364   using WeakUseVector = SmallVector<WeakUseTy, 4>;
365 
366   /// Used to collect all uses of weak objects in a function body.
367   ///
368   /// Part of the implementation of -Wrepeated-use-of-weak.
369   using WeakObjectUseMap =
370       llvm::SmallDenseMap<WeakObjectProfileTy, WeakUseVector, 8,
371                           WeakObjectProfileTy::DenseMapInfo>;
372 
373 private:
374   /// Used to collect all uses of weak objects in this function body.
375   ///
376   /// Part of the implementation of -Wrepeated-use-of-weak.
377   WeakObjectUseMap WeakObjectUses;
378 
379 protected:
380   FunctionScopeInfo(const FunctionScopeInfo&) = default;
381 
382 public:
FunctionScopeInfo(DiagnosticsEngine & Diag)383   FunctionScopeInfo(DiagnosticsEngine &Diag)
384       : Kind(SK_Function), HasBranchProtectedScope(false),
385         HasBranchIntoScope(false), HasIndirectGoto(false), HasMustTail(false),
386         HasDroppedStmt(false), HasOMPDeclareReductionCombiner(false),
387         HasFallthroughStmt(false), UsesFPIntrin(false),
388         HasPotentialAvailabilityViolations(false), ObjCShouldCallSuper(false),
389         ObjCIsDesignatedInit(false), ObjCWarnForNoDesignatedInitChain(false),
390         ObjCIsSecondaryInit(false), ObjCWarnForNoInitDelegation(false),
391         NeedsCoroutineSuspends(true), ErrorTrap(Diag) {}
392 
393   virtual ~FunctionScopeInfo();
394 
395   /// Determine whether an unrecoverable error has occurred within this
396   /// function. Note that this may return false even if the function body is
397   /// invalid, because the errors may be suppressed if they're caused by prior
398   /// invalid declarations.
399   ///
400   /// FIXME: Migrate the caller of this to use containsErrors() instead once
401   /// it's ready.
hasUnrecoverableErrorOccurred()402   bool hasUnrecoverableErrorOccurred() const {
403     return ErrorTrap.hasUnrecoverableErrorOccurred();
404   }
405 
406   /// Record that a weak object was accessed.
407   ///
408   /// Part of the implementation of -Wrepeated-use-of-weak.
409   template <typename ExprT>
410   inline void recordUseOfWeak(const ExprT *E, bool IsRead = true);
411 
412   void recordUseOfWeak(const ObjCMessageExpr *Msg,
413                        const ObjCPropertyDecl *Prop);
414 
415   /// Record that a given expression is a "safe" access of a weak object (e.g.
416   /// assigning it to a strong variable.)
417   ///
418   /// Part of the implementation of -Wrepeated-use-of-weak.
419   void markSafeWeakUse(const Expr *E);
420 
getWeakObjectUses()421   const WeakObjectUseMap &getWeakObjectUses() const {
422     return WeakObjectUses;
423   }
424 
setHasBranchIntoScope()425   void setHasBranchIntoScope() {
426     HasBranchIntoScope = true;
427   }
428 
setHasBranchProtectedScope()429   void setHasBranchProtectedScope() {
430     HasBranchProtectedScope = true;
431   }
432 
setHasIndirectGoto()433   void setHasIndirectGoto() {
434     HasIndirectGoto = true;
435   }
436 
setHasMustTail()437   void setHasMustTail() { HasMustTail = true; }
438 
setHasDroppedStmt()439   void setHasDroppedStmt() {
440     HasDroppedStmt = true;
441   }
442 
setHasOMPDeclareReductionCombiner()443   void setHasOMPDeclareReductionCombiner() {
444     HasOMPDeclareReductionCombiner = true;
445   }
446 
setHasFallthroughStmt()447   void setHasFallthroughStmt() {
448     HasFallthroughStmt = true;
449   }
450 
setUsesFPIntrin()451   void setUsesFPIntrin() {
452     UsesFPIntrin = true;
453   }
454 
setHasCXXTry(SourceLocation TryLoc)455   void setHasCXXTry(SourceLocation TryLoc) {
456     setHasBranchProtectedScope();
457     FirstCXXOrObjCTryLoc = TryLoc;
458     FirstTryType = TryLocIsCXX;
459   }
460 
setHasObjCTry(SourceLocation TryLoc)461   void setHasObjCTry(SourceLocation TryLoc) {
462     setHasBranchProtectedScope();
463     FirstCXXOrObjCTryLoc = TryLoc;
464     FirstTryType = TryLocIsObjC;
465   }
466 
setHasSEHTry(SourceLocation TryLoc)467   void setHasSEHTry(SourceLocation TryLoc) {
468     setHasBranchProtectedScope();
469     FirstSEHTryLoc = TryLoc;
470   }
471 
NeedsScopeChecking()472   bool NeedsScopeChecking() const {
473     return !HasDroppedStmt && (HasIndirectGoto || HasMustTail ||
474                                (HasBranchProtectedScope && HasBranchIntoScope));
475   }
476 
477   // Add a block introduced in this function.
addBlock(const BlockDecl * BD)478   void addBlock(const BlockDecl *BD) {
479     Blocks.insert(BD);
480   }
481 
482   // Add a __block variable introduced in this function.
addByrefBlockVar(VarDecl * VD)483   void addByrefBlockVar(VarDecl *VD) {
484     ByrefBlockVars.push_back(VD);
485   }
486 
isCoroutine()487   bool isCoroutine() const { return !FirstCoroutineStmtLoc.isInvalid(); }
488 
setFirstCoroutineStmt(SourceLocation Loc,StringRef Keyword)489   void setFirstCoroutineStmt(SourceLocation Loc, StringRef Keyword) {
490     assert(FirstCoroutineStmtLoc.isInvalid() &&
491                    "first coroutine statement location already set");
492     FirstCoroutineStmtLoc = Loc;
493     FirstCoroutineStmtKind = llvm::StringSwitch<unsigned char>(Keyword)
494             .Case("co_return", 0)
495             .Case("co_await", 1)
496             .Case("co_yield", 2);
497   }
498 
getFirstCoroutineStmtKeyword()499   StringRef getFirstCoroutineStmtKeyword() const {
500     assert(FirstCoroutineStmtLoc.isValid()
501                    && "no coroutine statement available");
502     switch (FirstCoroutineStmtKind) {
503     case 0: return "co_return";
504     case 1: return "co_await";
505     case 2: return "co_yield";
506     default:
507       llvm_unreachable("FirstCoroutineStmtKind has an invalid value");
508     };
509   }
510 
511   void setNeedsCoroutineSuspends(bool value = true) {
512     assert((!value || CoroutineSuspends.first == nullptr) &&
513             "we already have valid suspend points");
514     NeedsCoroutineSuspends = value;
515   }
516 
hasInvalidCoroutineSuspends()517   bool hasInvalidCoroutineSuspends() const {
518     return !NeedsCoroutineSuspends && CoroutineSuspends.first == nullptr;
519   }
520 
setCoroutineSuspends(Stmt * Initial,Stmt * Final)521   void setCoroutineSuspends(Stmt *Initial, Stmt *Final) {
522     assert(Initial && Final && "suspend points cannot be null");
523     assert(CoroutineSuspends.first == nullptr && "suspend points already set");
524     NeedsCoroutineSuspends = false;
525     CoroutineSuspends.first = Initial;
526     CoroutineSuspends.second = Final;
527   }
528 
529   /// Clear out the information in this function scope, making it
530   /// suitable for reuse.
531   void Clear();
532 
isPlainFunction()533   bool isPlainFunction() const { return Kind == SK_Function; }
534 };
535 
536 class Capture {
537   // There are three categories of capture: capturing 'this', capturing
538   // local variables, and C++1y initialized captures (which can have an
539   // arbitrary initializer, and don't really capture in the traditional
540   // sense at all).
541   //
542   // There are three ways to capture a local variable:
543   //  - capture by copy in the C++11 sense,
544   //  - capture by reference in the C++11 sense, and
545   //  - __block capture.
546   // Lambdas explicitly specify capture by copy or capture by reference.
547   // For blocks, __block capture applies to variables with that annotation,
548   // variables of reference type are captured by reference, and other
549   // variables are captured by copy.
550   enum CaptureKind {
551     Cap_ByCopy, Cap_ByRef, Cap_Block, Cap_VLA
552   };
553 
554   union {
555     /// If Kind == Cap_VLA, the captured type.
556     const VariableArrayType *CapturedVLA;
557 
558     /// Otherwise, the captured variable (if any).
559     ValueDecl *CapturedVar;
560   };
561 
562   /// The source location at which the first capture occurred.
563   SourceLocation Loc;
564 
565   /// The location of the ellipsis that expands a parameter pack.
566   SourceLocation EllipsisLoc;
567 
568   /// The type as it was captured, which is the type of the non-static data
569   /// member that would hold the capture.
570   QualType CaptureType;
571 
572   /// The CaptureKind of this capture.
573   unsigned Kind : 2;
574 
575   /// Whether this is a nested capture (a capture of an enclosing capturing
576   /// scope's capture).
577   unsigned Nested : 1;
578 
579   /// Whether this is a capture of '*this'.
580   unsigned CapturesThis : 1;
581 
582   /// Whether an explicit capture has been odr-used in the body of the
583   /// lambda.
584   unsigned ODRUsed : 1;
585 
586   /// Whether an explicit capture has been non-odr-used in the body of
587   /// the lambda.
588   unsigned NonODRUsed : 1;
589 
590   /// Whether the capture is invalid (a capture was required but the entity is
591   /// non-capturable).
592   unsigned Invalid : 1;
593 
594 public:
Capture(ValueDecl * Var,bool Block,bool ByRef,bool IsNested,SourceLocation Loc,SourceLocation EllipsisLoc,QualType CaptureType,bool Invalid)595   Capture(ValueDecl *Var, bool Block, bool ByRef, bool IsNested,
596           SourceLocation Loc, SourceLocation EllipsisLoc, QualType CaptureType,
597           bool Invalid)
598       : CapturedVar(Var), Loc(Loc), EllipsisLoc(EllipsisLoc),
599         CaptureType(CaptureType), Kind(Block   ? Cap_Block
600                                        : ByRef ? Cap_ByRef
601                                                : Cap_ByCopy),
602         Nested(IsNested), CapturesThis(false), ODRUsed(false),
603         NonODRUsed(false), Invalid(Invalid) {}
604 
605   enum IsThisCapture { ThisCapture };
Capture(IsThisCapture,bool IsNested,SourceLocation Loc,QualType CaptureType,const bool ByCopy,bool Invalid)606   Capture(IsThisCapture, bool IsNested, SourceLocation Loc,
607           QualType CaptureType, const bool ByCopy, bool Invalid)
608       : Loc(Loc), CaptureType(CaptureType),
609         Kind(ByCopy ? Cap_ByCopy : Cap_ByRef), Nested(IsNested),
610         CapturesThis(true), ODRUsed(false), NonODRUsed(false),
611         Invalid(Invalid) {}
612 
613   enum IsVLACapture { VLACapture };
Capture(IsVLACapture,const VariableArrayType * VLA,bool IsNested,SourceLocation Loc,QualType CaptureType)614   Capture(IsVLACapture, const VariableArrayType *VLA, bool IsNested,
615           SourceLocation Loc, QualType CaptureType)
616       : CapturedVLA(VLA), Loc(Loc), CaptureType(CaptureType), Kind(Cap_VLA),
617         Nested(IsNested), CapturesThis(false), ODRUsed(false),
618         NonODRUsed(false), Invalid(false) {}
619 
isThisCapture()620   bool isThisCapture() const { return CapturesThis; }
isVariableCapture()621   bool isVariableCapture() const {
622     return !isThisCapture() && !isVLATypeCapture();
623   }
624 
isCopyCapture()625   bool isCopyCapture() const { return Kind == Cap_ByCopy; }
isReferenceCapture()626   bool isReferenceCapture() const { return Kind == Cap_ByRef; }
isBlockCapture()627   bool isBlockCapture() const { return Kind == Cap_Block; }
isVLATypeCapture()628   bool isVLATypeCapture() const { return Kind == Cap_VLA; }
629 
isNested()630   bool isNested() const { return Nested; }
631 
isInvalid()632   bool isInvalid() const { return Invalid; }
633 
634   /// Determine whether this capture is an init-capture.
635   bool isInitCapture() const;
636 
isODRUsed()637   bool isODRUsed() const { return ODRUsed; }
isNonODRUsed()638   bool isNonODRUsed() const { return NonODRUsed; }
markUsed(bool IsODRUse)639   void markUsed(bool IsODRUse) {
640     if (IsODRUse)
641       ODRUsed = true;
642     else
643       NonODRUsed = true;
644   }
645 
getVariable()646   ValueDecl *getVariable() const {
647     assert(isVariableCapture());
648     return CapturedVar;
649   }
650 
getCapturedVLAType()651   const VariableArrayType *getCapturedVLAType() const {
652     assert(isVLATypeCapture());
653     return CapturedVLA;
654   }
655 
656   /// Retrieve the location at which this variable was captured.
getLocation()657   SourceLocation getLocation() const { return Loc; }
658 
659   /// Retrieve the source location of the ellipsis, whose presence
660   /// indicates that the capture is a pack expansion.
getEllipsisLoc()661   SourceLocation getEllipsisLoc() const { return EllipsisLoc; }
662 
663   /// Retrieve the capture type for this capture, which is effectively
664   /// the type of the non-static data member in the lambda/block structure
665   /// that would store this capture.
getCaptureType()666   QualType getCaptureType() const { return CaptureType; }
667 };
668 
669 class CapturingScopeInfo : public FunctionScopeInfo {
670 protected:
671   CapturingScopeInfo(const CapturingScopeInfo&) = default;
672 
673 public:
674   enum ImplicitCaptureStyle {
675     ImpCap_None, ImpCap_LambdaByval, ImpCap_LambdaByref, ImpCap_Block,
676     ImpCap_CapturedRegion
677   };
678 
679   ImplicitCaptureStyle ImpCaptureStyle;
680 
CapturingScopeInfo(DiagnosticsEngine & Diag,ImplicitCaptureStyle Style)681   CapturingScopeInfo(DiagnosticsEngine &Diag, ImplicitCaptureStyle Style)
682       : FunctionScopeInfo(Diag), ImpCaptureStyle(Style) {}
683 
684   /// CaptureMap - A map of captured variables to (index+1) into Captures.
685   llvm::DenseMap<ValueDecl *, unsigned> CaptureMap;
686 
687   /// CXXThisCaptureIndex - The (index+1) of the capture of 'this';
688   /// zero if 'this' is not captured.
689   unsigned CXXThisCaptureIndex = 0;
690 
691   /// Captures - The captures.
692   SmallVector<Capture, 4> Captures;
693 
694   /// - Whether the target type of return statements in this context
695   /// is deduced (e.g. a lambda or block with omitted return type).
696   bool HasImplicitReturnType = false;
697 
698   /// ReturnType - The target type of return statements in this context,
699   /// or null if unknown.
700   QualType ReturnType;
701 
addCapture(ValueDecl * Var,bool isBlock,bool isByref,bool isNested,SourceLocation Loc,SourceLocation EllipsisLoc,QualType CaptureType,bool Invalid)702   void addCapture(ValueDecl *Var, bool isBlock, bool isByref, bool isNested,
703                   SourceLocation Loc, SourceLocation EllipsisLoc,
704                   QualType CaptureType, bool Invalid) {
705     Captures.push_back(Capture(Var, isBlock, isByref, isNested, Loc,
706                                EllipsisLoc, CaptureType, Invalid));
707     CaptureMap[Var] = Captures.size();
708   }
709 
addVLATypeCapture(SourceLocation Loc,const VariableArrayType * VLAType,QualType CaptureType)710   void addVLATypeCapture(SourceLocation Loc, const VariableArrayType *VLAType,
711                          QualType CaptureType) {
712     Captures.push_back(Capture(Capture::VLACapture, VLAType,
713                                /*FIXME: IsNested*/ false, Loc, CaptureType));
714   }
715 
716   void addThisCapture(bool isNested, SourceLocation Loc, QualType CaptureType,
717                       bool ByCopy);
718 
719   /// Determine whether the C++ 'this' is captured.
isCXXThisCaptured()720   bool isCXXThisCaptured() const { return CXXThisCaptureIndex != 0; }
721 
722   /// Retrieve the capture of C++ 'this', if it has been captured.
getCXXThisCapture()723   Capture &getCXXThisCapture() {
724     assert(isCXXThisCaptured() && "this has not been captured");
725     return Captures[CXXThisCaptureIndex - 1];
726   }
727 
728   /// Determine whether the given variable has been captured.
isCaptured(ValueDecl * Var)729   bool isCaptured(ValueDecl *Var) const { return CaptureMap.count(Var); }
730 
731   /// Determine whether the given variable-array type has been captured.
732   bool isVLATypeCaptured(const VariableArrayType *VAT) const;
733 
734   /// Retrieve the capture of the given variable, if it has been
735   /// captured already.
getCapture(ValueDecl * Var)736   Capture &getCapture(ValueDecl *Var) {
737     assert(isCaptured(Var) && "Variable has not been captured");
738     return Captures[CaptureMap[Var] - 1];
739   }
740 
getCapture(ValueDecl * Var)741   const Capture &getCapture(ValueDecl *Var) const {
742     llvm::DenseMap<ValueDecl *, unsigned>::const_iterator Known =
743         CaptureMap.find(Var);
744     assert(Known != CaptureMap.end() && "Variable has not been captured");
745     return Captures[Known->second - 1];
746   }
747 
classof(const FunctionScopeInfo * FSI)748   static bool classof(const FunctionScopeInfo *FSI) {
749     return FSI->Kind == SK_Block || FSI->Kind == SK_Lambda
750                                  || FSI->Kind == SK_CapturedRegion;
751   }
752 };
753 
754 /// Retains information about a block that is currently being parsed.
755 class BlockScopeInfo final : public CapturingScopeInfo {
756 public:
757   BlockDecl *TheDecl;
758 
759   /// TheScope - This is the scope for the block itself, which contains
760   /// arguments etc.
761   Scope *TheScope;
762 
763   /// BlockType - The function type of the block, if one was given.
764   /// Its return type may be BuiltinType::Dependent.
765   QualType FunctionType;
766 
BlockScopeInfo(DiagnosticsEngine & Diag,Scope * BlockScope,BlockDecl * Block)767   BlockScopeInfo(DiagnosticsEngine &Diag, Scope *BlockScope, BlockDecl *Block)
768       : CapturingScopeInfo(Diag, ImpCap_Block), TheDecl(Block),
769         TheScope(BlockScope) {
770     Kind = SK_Block;
771   }
772 
773   ~BlockScopeInfo() override;
774 
classof(const FunctionScopeInfo * FSI)775   static bool classof(const FunctionScopeInfo *FSI) {
776     return FSI->Kind == SK_Block;
777   }
778 };
779 
780 /// Retains information about a captured region.
781 class CapturedRegionScopeInfo final : public CapturingScopeInfo {
782 public:
783   /// The CapturedDecl for this statement.
784   CapturedDecl *TheCapturedDecl;
785 
786   /// The captured record type.
787   RecordDecl *TheRecordDecl;
788 
789   /// This is the enclosing scope of the captured region.
790   Scope *TheScope;
791 
792   /// The implicit parameter for the captured variables.
793   ImplicitParamDecl *ContextParam;
794 
795   /// The kind of captured region.
796   unsigned short CapRegionKind;
797 
798   unsigned short OpenMPLevel;
799   unsigned short OpenMPCaptureLevel;
800 
CapturedRegionScopeInfo(DiagnosticsEngine & Diag,Scope * S,CapturedDecl * CD,RecordDecl * RD,ImplicitParamDecl * Context,CapturedRegionKind K,unsigned OpenMPLevel,unsigned OpenMPCaptureLevel)801   CapturedRegionScopeInfo(DiagnosticsEngine &Diag, Scope *S, CapturedDecl *CD,
802                           RecordDecl *RD, ImplicitParamDecl *Context,
803                           CapturedRegionKind K, unsigned OpenMPLevel,
804                           unsigned OpenMPCaptureLevel)
805       : CapturingScopeInfo(Diag, ImpCap_CapturedRegion),
806         TheCapturedDecl(CD), TheRecordDecl(RD), TheScope(S),
807         ContextParam(Context), CapRegionKind(K), OpenMPLevel(OpenMPLevel),
808         OpenMPCaptureLevel(OpenMPCaptureLevel) {
809     Kind = SK_CapturedRegion;
810   }
811 
812   ~CapturedRegionScopeInfo() override;
813 
814   /// A descriptive name for the kind of captured region this is.
getRegionName()815   StringRef getRegionName() const {
816     switch (CapRegionKind) {
817     case CR_Default:
818       return "default captured statement";
819     case CR_ObjCAtFinally:
820       return "Objective-C @finally statement";
821     case CR_OpenMP:
822       return "OpenMP region";
823     }
824     llvm_unreachable("Invalid captured region kind!");
825   }
826 
classof(const FunctionScopeInfo * FSI)827   static bool classof(const FunctionScopeInfo *FSI) {
828     return FSI->Kind == SK_CapturedRegion;
829   }
830 };
831 
832 class LambdaScopeInfo final :
833     public CapturingScopeInfo, public InventedTemplateParameterInfo {
834 public:
835   /// The class that describes the lambda.
836   CXXRecordDecl *Lambda = nullptr;
837 
838   /// The lambda's compiler-generated \c operator().
839   CXXMethodDecl *CallOperator = nullptr;
840 
841   /// Source range covering the lambda introducer [...].
842   SourceRange IntroducerRange;
843 
844   /// Source location of the '&' or '=' specifying the default capture
845   /// type, if any.
846   SourceLocation CaptureDefaultLoc;
847 
848   /// The number of captures in the \c Captures list that are
849   /// explicit captures.
850   unsigned NumExplicitCaptures = 0;
851 
852   /// Whether this is a mutable lambda.
853   bool Mutable = false;
854 
855   /// Whether the (empty) parameter list is explicit.
856   bool ExplicitParams = false;
857 
858   /// Whether any of the capture expressions requires cleanups.
859   CleanupInfo Cleanup;
860 
861   /// Whether the lambda contains an unexpanded parameter pack.
862   bool ContainsUnexpandedParameterPack = false;
863 
864   /// Packs introduced by this lambda, if any.
865   SmallVector<NamedDecl*, 4> LocalPacks;
866 
867   /// Source range covering the explicit template parameter list (if it exists).
868   SourceRange ExplicitTemplateParamsRange;
869 
870   /// The requires-clause immediately following the explicit template parameter
871   /// list, if any. (Note that there may be another requires-clause included as
872   /// part of the lambda-declarator.)
873   ExprResult RequiresClause;
874 
875   /// If this is a generic lambda, and the template parameter
876   /// list has been created (from the TemplateParams) then store
877   /// a reference to it (cache it to avoid reconstructing it).
878   TemplateParameterList *GLTemplateParameterList = nullptr;
879 
880   /// Contains all variable-referring-expressions (i.e. DeclRefExprs
881   ///  or MemberExprs) that refer to local variables in a generic lambda
882   ///  or a lambda in a potentially-evaluated-if-used context.
883   ///
884   ///  Potentially capturable variables of a nested lambda that might need
885   ///   to be captured by the lambda are housed here.
886   ///  This is specifically useful for generic lambdas or
887   ///  lambdas within a potentially evaluated-if-used context.
888   ///  If an enclosing variable is named in an expression of a lambda nested
889   ///  within a generic lambda, we don't always know whether the variable
890   ///  will truly be odr-used (i.e. need to be captured) by that nested lambda,
891   ///  until its instantiation. But we still need to capture it in the
892   ///  enclosing lambda if all intervening lambdas can capture the variable.
893   llvm::SmallVector<Expr*, 4> PotentiallyCapturingExprs;
894 
895   /// Contains all variable-referring-expressions that refer
896   ///  to local variables that are usable as constant expressions and
897   ///  do not involve an odr-use (they may still need to be captured
898   ///  if the enclosing full-expression is instantiation dependent).
899   llvm::SmallSet<Expr *, 8> NonODRUsedCapturingExprs;
900 
901   /// A map of explicit capture indices to their introducer source ranges.
902   llvm::DenseMap<unsigned, SourceRange> ExplicitCaptureRanges;
903 
904   /// Contains all of the variables defined in this lambda that shadow variables
905   /// that were defined in parent contexts. Used to avoid warnings when the
906   /// shadowed variables are uncaptured by this lambda.
907   struct ShadowedOuterDecl {
908     const VarDecl *VD;
909     const VarDecl *ShadowedDecl;
910   };
911   llvm::SmallVector<ShadowedOuterDecl, 4> ShadowingDecls;
912 
913   SourceLocation PotentialThisCaptureLocation;
914 
LambdaScopeInfo(DiagnosticsEngine & Diag)915   LambdaScopeInfo(DiagnosticsEngine &Diag)
916       : CapturingScopeInfo(Diag, ImpCap_None) {
917     Kind = SK_Lambda;
918   }
919 
920   /// Note when all explicit captures have been added.
finishedExplicitCaptures()921   void finishedExplicitCaptures() {
922     NumExplicitCaptures = Captures.size();
923   }
924 
classof(const FunctionScopeInfo * FSI)925   static bool classof(const FunctionScopeInfo *FSI) {
926     return FSI->Kind == SK_Lambda;
927   }
928 
929   /// Is this scope known to be for a generic lambda? (This will be false until
930   /// we parse a template parameter list or the first 'auto'-typed parameter).
isGenericLambda()931   bool isGenericLambda() const {
932     return !TemplateParams.empty() || GLTemplateParameterList;
933   }
934 
935   /// Add a variable that might potentially be captured by the
936   /// lambda and therefore the enclosing lambdas.
937   ///
938   /// This is also used by enclosing lambda's to speculatively capture
939   /// variables that nested lambda's - depending on their enclosing
940   /// specialization - might need to capture.
941   /// Consider:
942   /// void f(int, int); <-- don't capture
943   /// void f(const int&, double); <-- capture
944   /// void foo() {
945   ///   const int x = 10;
946   ///   auto L = [=](auto a) { // capture 'x'
947   ///      return [=](auto b) {
948   ///        f(x, a);  // we may or may not need to capture 'x'
949   ///      };
950   ///   };
951   /// }
addPotentialCapture(Expr * VarExpr)952   void addPotentialCapture(Expr *VarExpr) {
953     assert(isa<DeclRefExpr>(VarExpr) || isa<MemberExpr>(VarExpr) ||
954            isa<FunctionParmPackExpr>(VarExpr));
955     PotentiallyCapturingExprs.push_back(VarExpr);
956   }
957 
addPotentialThisCapture(SourceLocation Loc)958   void addPotentialThisCapture(SourceLocation Loc) {
959     PotentialThisCaptureLocation = Loc;
960   }
961 
hasPotentialThisCapture()962   bool hasPotentialThisCapture() const {
963     return PotentialThisCaptureLocation.isValid();
964   }
965 
966   /// Mark a variable's reference in a lambda as non-odr using.
967   ///
968   /// For generic lambdas, if a variable is named in a potentially evaluated
969   /// expression, where the enclosing full expression is dependent then we
970   /// must capture the variable (given a default capture).
971   /// This is accomplished by recording all references to variables
972   /// (DeclRefExprs or MemberExprs) within said nested lambda in its array of
973   /// PotentialCaptures. All such variables have to be captured by that lambda,
974   /// except for as described below.
975   /// If that variable is usable as a constant expression and is named in a
976   /// manner that does not involve its odr-use (e.g. undergoes
977   /// lvalue-to-rvalue conversion, or discarded) record that it is so. Upon the
978   /// act of analyzing the enclosing full expression (ActOnFinishFullExpr)
979   /// if we can determine that the full expression is not instantiation-
980   /// dependent, then we can entirely avoid its capture.
981   ///
982   ///   const int n = 0;
983   ///   [&] (auto x) {
984   ///     (void)+n + x;
985   ///   };
986   /// Interestingly, this strategy would involve a capture of n, even though
987   /// it's obviously not odr-used here, because the full-expression is
988   /// instantiation-dependent.  It could be useful to avoid capturing such
989   /// variables, even when they are referred to in an instantiation-dependent
990   /// expression, if we can unambiguously determine that they shall never be
991   /// odr-used.  This would involve removal of the variable-referring-expression
992   /// from the array of PotentialCaptures during the lvalue-to-rvalue
993   /// conversions.  But per the working draft N3797, (post-chicago 2013) we must
994   /// capture such variables.
995   /// Before anyone is tempted to implement a strategy for not-capturing 'n',
996   /// consider the insightful warning in:
997   ///    /cfe-commits/Week-of-Mon-20131104/092596.html
998   /// "The problem is that the set of captures for a lambda is part of the ABI
999   ///  (since lambda layout can be made visible through inline functions and the
1000   ///  like), and there are no guarantees as to which cases we'll manage to build
1001   ///  an lvalue-to-rvalue conversion in, when parsing a template -- some
1002   ///  seemingly harmless change elsewhere in Sema could cause us to start or stop
1003   ///  building such a node. So we need a rule that anyone can implement and get
1004   ///  exactly the same result".
markVariableExprAsNonODRUsed(Expr * CapturingVarExpr)1005   void markVariableExprAsNonODRUsed(Expr *CapturingVarExpr) {
1006     assert(isa<DeclRefExpr>(CapturingVarExpr) ||
1007            isa<MemberExpr>(CapturingVarExpr) ||
1008            isa<FunctionParmPackExpr>(CapturingVarExpr));
1009     NonODRUsedCapturingExprs.insert(CapturingVarExpr);
1010   }
isVariableExprMarkedAsNonODRUsed(Expr * CapturingVarExpr)1011   bool isVariableExprMarkedAsNonODRUsed(Expr *CapturingVarExpr) const {
1012     assert(isa<DeclRefExpr>(CapturingVarExpr) ||
1013            isa<MemberExpr>(CapturingVarExpr) ||
1014            isa<FunctionParmPackExpr>(CapturingVarExpr));
1015     return NonODRUsedCapturingExprs.count(CapturingVarExpr);
1016   }
removePotentialCapture(Expr * E)1017   void removePotentialCapture(Expr *E) {
1018     llvm::erase_value(PotentiallyCapturingExprs, E);
1019   }
clearPotentialCaptures()1020   void clearPotentialCaptures() {
1021     PotentiallyCapturingExprs.clear();
1022     PotentialThisCaptureLocation = SourceLocation();
1023   }
getNumPotentialVariableCaptures()1024   unsigned getNumPotentialVariableCaptures() const {
1025     return PotentiallyCapturingExprs.size();
1026   }
1027 
hasPotentialCaptures()1028   bool hasPotentialCaptures() const {
1029     return getNumPotentialVariableCaptures() ||
1030                                   PotentialThisCaptureLocation.isValid();
1031   }
1032 
1033   void visitPotentialCaptures(
1034       llvm::function_ref<void(ValueDecl *, Expr *)> Callback) const;
1035 };
1036 
WeakObjectProfileTy()1037 FunctionScopeInfo::WeakObjectProfileTy::WeakObjectProfileTy()
1038     : Base(nullptr, false) {}
1039 
1040 FunctionScopeInfo::WeakObjectProfileTy
getSentinel()1041 FunctionScopeInfo::WeakObjectProfileTy::getSentinel() {
1042   FunctionScopeInfo::WeakObjectProfileTy Result;
1043   Result.Base.setInt(true);
1044   return Result;
1045 }
1046 
1047 template <typename ExprT>
recordUseOfWeak(const ExprT * E,bool IsRead)1048 void FunctionScopeInfo::recordUseOfWeak(const ExprT *E, bool IsRead) {
1049   assert(E);
1050   WeakUseVector &Uses = WeakObjectUses[WeakObjectProfileTy(E)];
1051   Uses.push_back(WeakUseTy(E, IsRead));
1052 }
1053 
addThisCapture(bool isNested,SourceLocation Loc,QualType CaptureType,bool ByCopy)1054 inline void CapturingScopeInfo::addThisCapture(bool isNested,
1055                                                SourceLocation Loc,
1056                                                QualType CaptureType,
1057                                                bool ByCopy) {
1058   Captures.push_back(Capture(Capture::ThisCapture, isNested, Loc, CaptureType,
1059                              ByCopy, /*Invalid*/ false));
1060   CXXThisCaptureIndex = Captures.size();
1061 }
1062 
1063 } // namespace sema
1064 
1065 } // namespace clang
1066 
1067 #endif // LLVM_CLANG_SEMA_SCOPEINFO_H
1068