1 //===------ CXXInheritance.cpp - C++ Inheritance ----------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file provides routines that help analyzing C++ inheritance hierarchies.
12 //===----------------------------------------------------------------------===//
13 #include "clang/AST/CXXInheritance.h"
14 #include "clang/AST/ASTContext.h"
15 #include "clang/AST/DeclCXX.h"
16 #include "clang/AST/RecordLayout.h"
17 #include "llvm/ADT/SetVector.h"
21 using namespace clang;
23 /// \brief Computes the set of declarations referenced by these base
25 void CXXBasePaths::ComputeDeclsFound() {
26 assert(NumDeclsFound == 0 && !DeclsFound &&
27 "Already computed the set of declarations");
29 llvm::SetVector<NamedDecl *, SmallVector<NamedDecl *, 8> > Decls;
30 for (paths_iterator Path = begin(), PathEnd = end(); Path != PathEnd; ++Path)
31 Decls.insert(Path->Decls.front());
33 NumDeclsFound = Decls.size();
34 DeclsFound = new NamedDecl * [NumDeclsFound];
35 std::copy(Decls.begin(), Decls.end(), DeclsFound);
38 CXXBasePaths::decl_range CXXBasePaths::found_decls() {
39 if (NumDeclsFound == 0)
42 return decl_range(decl_iterator(DeclsFound),
43 decl_iterator(DeclsFound + NumDeclsFound));
46 /// isAmbiguous - Determines whether the set of paths provided is
47 /// ambiguous, i.e., there are two or more paths that refer to
48 /// different base class subobjects of the same type. BaseType must be
49 /// an unqualified, canonical class type.
50 bool CXXBasePaths::isAmbiguous(CanQualType BaseType) {
51 BaseType = BaseType.getUnqualifiedType();
52 std::pair<bool, unsigned>& Subobjects = ClassSubobjects[BaseType];
53 return Subobjects.second + (Subobjects.first? 1 : 0) > 1;
56 /// clear - Clear out all prior path information.
57 void CXXBasePaths::clear() {
59 ClassSubobjects.clear();
61 DetectedVirtual = nullptr;
64 /// @brief Swaps the contents of this CXXBasePaths structure with the
65 /// contents of Other.
66 void CXXBasePaths::swap(CXXBasePaths &Other) {
67 std::swap(Origin, Other.Origin);
68 Paths.swap(Other.Paths);
69 ClassSubobjects.swap(Other.ClassSubobjects);
70 std::swap(FindAmbiguities, Other.FindAmbiguities);
71 std::swap(RecordPaths, Other.RecordPaths);
72 std::swap(DetectVirtual, Other.DetectVirtual);
73 std::swap(DetectedVirtual, Other.DetectedVirtual);
76 bool CXXRecordDecl::isDerivedFrom(const CXXRecordDecl *Base) const {
77 CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/false,
78 /*DetectVirtual=*/false);
79 return isDerivedFrom(Base, Paths);
82 bool CXXRecordDecl::isDerivedFrom(const CXXRecordDecl *Base,
83 CXXBasePaths &Paths) const {
84 if (getCanonicalDecl() == Base->getCanonicalDecl())
87 Paths.setOrigin(const_cast<CXXRecordDecl*>(this));
88 return lookupInBases(&FindBaseClass,
89 const_cast<CXXRecordDecl*>(Base->getCanonicalDecl()),
93 bool CXXRecordDecl::isVirtuallyDerivedFrom(const CXXRecordDecl *Base) const {
97 CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/false,
98 /*DetectVirtual=*/false);
100 if (getCanonicalDecl() == Base->getCanonicalDecl())
103 Paths.setOrigin(const_cast<CXXRecordDecl*>(this));
105 const void *BasePtr = static_cast<const void*>(Base->getCanonicalDecl());
106 return lookupInBases(&FindVirtualBaseClass,
107 const_cast<void *>(BasePtr),
111 static bool BaseIsNot(const CXXRecordDecl *Base, void *OpaqueTarget) {
112 // OpaqueTarget is a CXXRecordDecl*.
113 return Base->getCanonicalDecl() != (const CXXRecordDecl*) OpaqueTarget;
116 bool CXXRecordDecl::isProvablyNotDerivedFrom(const CXXRecordDecl *Base) const {
117 return forallBases(BaseIsNot,
118 const_cast<CXXRecordDecl *>(Base->getCanonicalDecl()));
122 CXXRecordDecl::isCurrentInstantiation(const DeclContext *CurContext) const {
123 assert(isDependentContext());
125 for (; !CurContext->isFileContext(); CurContext = CurContext->getParent())
126 if (CurContext->Equals(this))
132 bool CXXRecordDecl::forallBases(ForallBasesCallback *BaseMatches,
134 bool AllowShortCircuit) const {
135 SmallVector<const CXXRecordDecl*, 8> Queue;
137 const CXXRecordDecl *Record = this;
138 bool AllMatches = true;
140 for (const auto &I : Record->bases()) {
141 const RecordType *Ty = I.getType()->getAs<RecordType>();
143 if (AllowShortCircuit) return false;
148 CXXRecordDecl *Base =
149 cast_or_null<CXXRecordDecl>(Ty->getDecl()->getDefinition());
151 (Base->isDependentContext() &&
152 !Base->isCurrentInstantiation(Record))) {
153 if (AllowShortCircuit) return false;
158 Queue.push_back(Base);
159 if (!BaseMatches(Base, OpaqueData)) {
160 if (AllowShortCircuit) return false;
168 Record = Queue.pop_back_val(); // not actually a queue.
174 bool CXXBasePaths::lookupInBases(ASTContext &Context,
175 const CXXRecordDecl *Record,
176 CXXRecordDecl::BaseMatchesCallback *BaseMatches,
178 bool FoundPath = false;
180 // The access of the path down to this record.
181 AccessSpecifier AccessToHere = ScratchPath.Access;
182 bool IsFirstStep = ScratchPath.empty();
184 for (const auto &BaseSpec : Record->bases()) {
185 // Find the record of the base class subobjects for this type.
187 Context.getCanonicalType(BaseSpec.getType()).getUnqualifiedType();
190 // In the definition of a class template or a member of a class template,
191 // if a base class of the class template depends on a template-parameter,
192 // the base class scope is not examined during unqualified name lookup
193 // either at the point of definition of the class template or member or
194 // during an instantiation of the class tem- plate or member.
195 if (BaseType->isDependentType())
198 // Determine whether we need to visit this base class at all,
199 // updating the count of subobjects appropriately.
200 std::pair<bool, unsigned>& Subobjects = ClassSubobjects[BaseType];
201 bool VisitBase = true;
202 bool SetVirtual = false;
203 if (BaseSpec.isVirtual()) {
204 VisitBase = !Subobjects.first;
205 Subobjects.first = true;
206 if (isDetectingVirtual() && DetectedVirtual == nullptr) {
207 // If this is the first virtual we find, remember it. If it turns out
208 // there is no base path here, we'll reset it later.
209 DetectedVirtual = BaseType->getAs<RecordType>();
215 if (isRecordingPaths()) {
216 // Add this base specifier to the current path.
217 CXXBasePathElement Element;
218 Element.Base = &BaseSpec;
219 Element.Class = Record;
220 if (BaseSpec.isVirtual())
221 Element.SubobjectNumber = 0;
223 Element.SubobjectNumber = Subobjects.second;
224 ScratchPath.push_back(Element);
226 // Calculate the "top-down" access to this base class.
227 // The spec actually describes this bottom-up, but top-down is
228 // equivalent because the definition works out as follows:
229 // 1. Write down the access along each step in the inheritance
230 // chain, followed by the access of the decl itself.
232 // class A { public: int foo; };
233 // class B : protected A {};
234 // class C : public B {};
235 // class D : private C {};
237 // private public protected public
238 // 2. If 'private' appears anywhere except far-left, access is denied.
239 // 3. Otherwise, overall access is determined by the most restrictive
240 // access in the sequence.
242 ScratchPath.Access = BaseSpec.getAccessSpecifier();
244 ScratchPath.Access = CXXRecordDecl::MergeAccess(AccessToHere,
245 BaseSpec.getAccessSpecifier());
248 // Track whether there's a path involving this specific base.
249 bool FoundPathThroughBase = false;
251 if (BaseMatches(&BaseSpec, ScratchPath, UserData)) {
252 // We've found a path that terminates at this base.
253 FoundPath = FoundPathThroughBase = true;
254 if (isRecordingPaths()) {
255 // We have a path. Make a copy of it before moving on.
256 Paths.push_back(ScratchPath);
257 } else if (!isFindingAmbiguities()) {
258 // We found a path and we don't care about ambiguities;
259 // return immediately.
262 } else if (VisitBase) {
263 CXXRecordDecl *BaseRecord
264 = cast<CXXRecordDecl>(BaseSpec.getType()->castAs<RecordType>()
266 if (lookupInBases(Context, BaseRecord, BaseMatches, UserData)) {
267 // C++ [class.member.lookup]p2:
268 // A member name f in one sub-object B hides a member name f in
269 // a sub-object A if A is a base class sub-object of B. Any
270 // declarations that are so hidden are eliminated from
273 // There is a path to a base class that meets the criteria. If we're
274 // not collecting paths or finding ambiguities, we're done.
275 FoundPath = FoundPathThroughBase = true;
276 if (!isFindingAmbiguities())
281 // Pop this base specifier off the current path (if we're
282 // collecting paths).
283 if (isRecordingPaths()) {
284 ScratchPath.pop_back();
287 // If we set a virtual earlier, and this isn't a path, forget it again.
288 if (SetVirtual && !FoundPathThroughBase) {
289 DetectedVirtual = nullptr;
293 // Reset the scratch path access.
294 ScratchPath.Access = AccessToHere;
299 bool CXXRecordDecl::lookupInBases(BaseMatchesCallback *BaseMatches,
301 CXXBasePaths &Paths) const {
302 // If we didn't find anything, report that.
303 if (!Paths.lookupInBases(getASTContext(), this, BaseMatches, UserData))
306 // If we're not recording paths or we won't ever find ambiguities,
308 if (!Paths.isRecordingPaths() || !Paths.isFindingAmbiguities())
311 // C++ [class.member.lookup]p6:
312 // When virtual base classes are used, a hidden declaration can be
313 // reached along a path through the sub-object lattice that does
314 // not pass through the hiding declaration. This is not an
315 // ambiguity. The identical use with nonvirtual base classes is an
316 // ambiguity; in that case there is no unique instance of the name
317 // that hides all the others.
319 // FIXME: This is an O(N^2) algorithm, but DPG doesn't see an easy
320 // way to make it any faster.
321 Paths.Paths.remove_if([&Paths](const CXXBasePath &Path) {
322 for (const CXXBasePathElement &PE : Path) {
323 if (!PE.Base->isVirtual())
326 CXXRecordDecl *VBase = nullptr;
327 if (const RecordType *Record = PE.Base->getType()->getAs<RecordType>())
328 VBase = cast<CXXRecordDecl>(Record->getDecl());
332 // The declaration(s) we found along this path were found in a
333 // subobject of a virtual base. Check whether this virtual
334 // base is a subobject of any other path; if so, then the
335 // declaration in this path are hidden by that patch.
336 for (const CXXBasePath &HidingP : Paths) {
337 CXXRecordDecl *HidingClass = nullptr;
338 if (const RecordType *Record =
339 HidingP.back().Base->getType()->getAs<RecordType>())
340 HidingClass = cast<CXXRecordDecl>(Record->getDecl());
344 if (HidingClass->isVirtuallyDerivedFrom(VBase))
354 bool CXXRecordDecl::FindBaseClass(const CXXBaseSpecifier *Specifier,
357 assert(((Decl *)BaseRecord)->getCanonicalDecl() == BaseRecord &&
358 "User data for FindBaseClass is not canonical!");
359 return Specifier->getType()->castAs<RecordType>()->getDecl()
360 ->getCanonicalDecl() == BaseRecord;
363 bool CXXRecordDecl::FindVirtualBaseClass(const CXXBaseSpecifier *Specifier,
366 assert(((Decl *)BaseRecord)->getCanonicalDecl() == BaseRecord &&
367 "User data for FindBaseClass is not canonical!");
368 return Specifier->isVirtual() &&
369 Specifier->getType()->castAs<RecordType>()->getDecl()
370 ->getCanonicalDecl() == BaseRecord;
373 bool CXXRecordDecl::FindTagMember(const CXXBaseSpecifier *Specifier,
376 RecordDecl *BaseRecord =
377 Specifier->getType()->castAs<RecordType>()->getDecl();
379 DeclarationName N = DeclarationName::getFromOpaquePtr(Name);
380 for (Path.Decls = BaseRecord->lookup(N);
382 Path.Decls = Path.Decls.slice(1)) {
383 if (Path.Decls.front()->isInIdentifierNamespace(IDNS_Tag))
390 bool CXXRecordDecl::FindOrdinaryMember(const CXXBaseSpecifier *Specifier,
393 RecordDecl *BaseRecord =
394 Specifier->getType()->castAs<RecordType>()->getDecl();
396 const unsigned IDNS = IDNS_Ordinary | IDNS_Tag | IDNS_Member;
397 DeclarationName N = DeclarationName::getFromOpaquePtr(Name);
398 for (Path.Decls = BaseRecord->lookup(N);
400 Path.Decls = Path.Decls.slice(1)) {
401 if (Path.Decls.front()->isInIdentifierNamespace(IDNS))
409 FindNestedNameSpecifierMember(const CXXBaseSpecifier *Specifier,
412 RecordDecl *BaseRecord =
413 Specifier->getType()->castAs<RecordType>()->getDecl();
415 DeclarationName N = DeclarationName::getFromOpaquePtr(Name);
416 for (Path.Decls = BaseRecord->lookup(N);
418 Path.Decls = Path.Decls.slice(1)) {
419 // FIXME: Refactor the "is it a nested-name-specifier?" check
420 if (isa<TypedefNameDecl>(Path.Decls.front()) ||
421 Path.Decls.front()->isInIdentifierNamespace(IDNS_Tag))
428 void OverridingMethods::add(unsigned OverriddenSubobject,
429 UniqueVirtualMethod Overriding) {
430 SmallVectorImpl<UniqueVirtualMethod> &SubobjectOverrides
431 = Overrides[OverriddenSubobject];
432 if (std::find(SubobjectOverrides.begin(), SubobjectOverrides.end(),
433 Overriding) == SubobjectOverrides.end())
434 SubobjectOverrides.push_back(Overriding);
437 void OverridingMethods::add(const OverridingMethods &Other) {
438 for (const_iterator I = Other.begin(), IE = Other.end(); I != IE; ++I) {
439 for (overriding_const_iterator M = I->second.begin(),
440 MEnd = I->second.end();
447 void OverridingMethods::replaceAll(UniqueVirtualMethod Overriding) {
448 for (iterator I = begin(), IEnd = end(); I != IEnd; ++I) {
450 I->second.push_back(Overriding);
456 class FinalOverriderCollector {
457 /// \brief The number of subobjects of a given class type that
458 /// occur within the class hierarchy.
459 llvm::DenseMap<const CXXRecordDecl *, unsigned> SubobjectCount;
461 /// \brief Overriders for each virtual base subobject.
462 llvm::DenseMap<const CXXRecordDecl *, CXXFinalOverriderMap *> VirtualOverriders;
464 CXXFinalOverriderMap FinalOverriders;
467 ~FinalOverriderCollector();
469 void Collect(const CXXRecordDecl *RD, bool VirtualBase,
470 const CXXRecordDecl *InVirtualSubobject,
471 CXXFinalOverriderMap &Overriders);
475 void FinalOverriderCollector::Collect(const CXXRecordDecl *RD,
477 const CXXRecordDecl *InVirtualSubobject,
478 CXXFinalOverriderMap &Overriders) {
479 unsigned SubobjectNumber = 0;
482 = ++SubobjectCount[cast<CXXRecordDecl>(RD->getCanonicalDecl())];
484 for (const auto &Base : RD->bases()) {
485 if (const RecordType *RT = Base.getType()->getAs<RecordType>()) {
486 const CXXRecordDecl *BaseDecl = cast<CXXRecordDecl>(RT->getDecl());
487 if (!BaseDecl->isPolymorphic())
490 if (Overriders.empty() && !Base.isVirtual()) {
491 // There are no other overriders of virtual member functions,
492 // so let the base class fill in our overriders for us.
493 Collect(BaseDecl, false, InVirtualSubobject, Overriders);
497 // Collect all of the overridders from the base class subobject
498 // and merge them into the set of overridders for this class.
499 // For virtual base classes, populate or use the cached virtual
500 // overrides so that we do not walk the virtual base class (and
501 // its base classes) more than once.
502 CXXFinalOverriderMap ComputedBaseOverriders;
503 CXXFinalOverriderMap *BaseOverriders = &ComputedBaseOverriders;
504 if (Base.isVirtual()) {
505 CXXFinalOverriderMap *&MyVirtualOverriders = VirtualOverriders[BaseDecl];
506 BaseOverriders = MyVirtualOverriders;
507 if (!MyVirtualOverriders) {
508 MyVirtualOverriders = new CXXFinalOverriderMap;
510 // Collect may cause VirtualOverriders to reallocate, invalidating the
511 // MyVirtualOverriders reference. Set BaseOverriders to the right
513 BaseOverriders = MyVirtualOverriders;
515 Collect(BaseDecl, true, BaseDecl, *MyVirtualOverriders);
518 Collect(BaseDecl, false, InVirtualSubobject, ComputedBaseOverriders);
520 // Merge the overriders from this base class into our own set of
522 for (CXXFinalOverriderMap::iterator OM = BaseOverriders->begin(),
523 OMEnd = BaseOverriders->end();
526 const CXXMethodDecl *CanonOM
527 = cast<CXXMethodDecl>(OM->first->getCanonicalDecl());
528 Overriders[CanonOM].add(OM->second);
533 for (auto *M : RD->methods()) {
534 // We only care about virtual methods.
538 CXXMethodDecl *CanonM = cast<CXXMethodDecl>(M->getCanonicalDecl());
540 if (CanonM->begin_overridden_methods()
541 == CanonM->end_overridden_methods()) {
542 // This is a new virtual function that does not override any
543 // other virtual function. Add it to the map of virtual
544 // functions for which we are tracking overridders.
546 // C++ [class.virtual]p2:
547 // For convenience we say that any virtual function overrides itself.
548 Overriders[CanonM].add(SubobjectNumber,
549 UniqueVirtualMethod(CanonM, SubobjectNumber,
550 InVirtualSubobject));
554 // This virtual method overrides other virtual methods, so it does
555 // not add any new slots into the set of overriders. Instead, we
556 // replace entries in the set of overriders with the new
557 // overrider. To do so, we dig down to the original virtual
558 // functions using data recursion and update all of the methods it
560 typedef llvm::iterator_range<CXXMethodDecl::method_iterator>
562 SmallVector<OverriddenMethods, 4> Stack;
563 Stack.push_back(llvm::make_range(CanonM->begin_overridden_methods(),
564 CanonM->end_overridden_methods()));
565 while (!Stack.empty()) {
566 for (const CXXMethodDecl *OM : Stack.pop_back_val()) {
567 const CXXMethodDecl *CanonOM = OM->getCanonicalDecl();
569 // C++ [class.virtual]p2:
570 // A virtual member function C::vf of a class object S is
571 // a final overrider unless the most derived class (1.8)
572 // of which S is a base class subobject (if any) declares
573 // or inherits another member function that overrides vf.
575 // Treating this object like the most derived class, we
576 // replace any overrides from base classes with this
577 // overriding virtual function.
578 Overriders[CanonOM].replaceAll(
579 UniqueVirtualMethod(CanonM, SubobjectNumber,
580 InVirtualSubobject));
582 if (CanonOM->begin_overridden_methods()
583 == CanonOM->end_overridden_methods())
586 // Continue recursion to the methods that this virtual method
588 Stack.push_back(llvm::make_range(CanonOM->begin_overridden_methods(),
589 CanonOM->end_overridden_methods()));
593 // C++ [class.virtual]p2:
594 // For convenience we say that any virtual function overrides itself.
595 Overriders[CanonM].add(SubobjectNumber,
596 UniqueVirtualMethod(CanonM, SubobjectNumber,
597 InVirtualSubobject));
601 FinalOverriderCollector::~FinalOverriderCollector() {
602 for (llvm::DenseMap<const CXXRecordDecl *, CXXFinalOverriderMap *>::iterator
603 VO = VirtualOverriders.begin(), VOEnd = VirtualOverriders.end();
610 CXXRecordDecl::getFinalOverriders(CXXFinalOverriderMap &FinalOverriders) const {
611 FinalOverriderCollector Collector;
612 Collector.Collect(this, false, nullptr, FinalOverriders);
614 // Weed out any final overriders that come from virtual base class
615 // subobjects that were hidden by other subobjects along any path.
616 // This is the final-overrider variant of C++ [class.member.lookup]p10.
617 for (auto &OM : FinalOverriders) {
618 for (auto &SO : OM.second) {
619 SmallVectorImpl<UniqueVirtualMethod> &Overriding = SO.second;
620 if (Overriding.size() < 2)
623 auto IsHidden = [&Overriding](const UniqueVirtualMethod &M) {
624 if (!M.InVirtualSubobject)
627 // We have an overriding method in a virtual base class
628 // subobject (or non-virtual base class subobject thereof);
629 // determine whether there exists an other overriding method
630 // in a base class subobject that hides the virtual base class
632 for (const UniqueVirtualMethod &OP : Overriding)
634 OP.Method->getParent()->isVirtuallyDerivedFrom(
635 M.InVirtualSubobject))
641 std::remove_if(Overriding.begin(), Overriding.end(), IsHidden),
648 AddIndirectPrimaryBases(const CXXRecordDecl *RD, ASTContext &Context,
649 CXXIndirectPrimaryBaseSet& Bases) {
650 // If the record has a virtual primary base class, add it to our set.
651 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
652 if (Layout.isPrimaryBaseVirtual())
653 Bases.insert(Layout.getPrimaryBase());
655 for (const auto &I : RD->bases()) {
656 assert(!I.getType()->isDependentType() &&
657 "Cannot get indirect primary bases for class with dependent bases.");
659 const CXXRecordDecl *BaseDecl =
660 cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
662 // Only bases with virtual bases participate in computing the
663 // indirect primary virtual base classes.
664 if (BaseDecl->getNumVBases())
665 AddIndirectPrimaryBases(BaseDecl, Context, Bases);
671 CXXRecordDecl::getIndirectPrimaryBases(CXXIndirectPrimaryBaseSet& Bases) const {
672 ASTContext &Context = getASTContext();
677 for (const auto &I : bases()) {
678 assert(!I.getType()->isDependentType() &&
679 "Cannot get indirect primary bases for class with dependent bases.");
681 const CXXRecordDecl *BaseDecl =
682 cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
684 // Only bases with virtual bases participate in computing the
685 // indirect primary virtual base classes.
686 if (BaseDecl->getNumVBases())
687 AddIndirectPrimaryBases(BaseDecl, Context, Bases);