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