// CanUseSingleInheritance - Return whether the given record decl has a "single,
// public, non-virtual base at offset zero (i.e. the derived class is dynamic
// iff the base is)", according to Itanium C++ ABI, 2.95p6b.
static bool CanUseSingleInheritance(const CXXRecordDecl *RD) {
// Check the number of bases.
if (RD->getNumBases() != 1)
return false;
// Get the base.
CXXRecordDecl::base_class_const_iterator Base = RD->bases_begin();
// Check that the base is not virtual.
if (Base->isVirtual())
return false;
// Check that the base is public.
if (Base->getAccessSpecifier() != AS_public)
return false;
// Check that the class is dynamic iff the base is.
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(Base->getType()->getAs<RecordType>()->getDecl());
if (!BaseDecl->isEmpty() &&
BaseDecl->isDynamicClass() != RD->isDynamicClass())
return false;
return true;
}
bool CXXBasePaths::lookupInBases(ASTContext &Context,
const CXXRecordDecl *Record,
CXXRecordDecl::BaseMatchesCallback *BaseMatches,
void *UserData) {
bool FoundPath = false;
// The access of the path down to this record.
AccessSpecifier AccessToHere = ScratchPath.Access;
bool IsFirstStep = ScratchPath.empty();
for (CXXRecordDecl::base_class_const_iterator BaseSpec = Record->bases_begin(),
BaseSpecEnd = Record->bases_end();
BaseSpec != BaseSpecEnd;
++BaseSpec) {
// Find the record of the base class subobjects for this type.
QualType BaseType = Context.getCanonicalType(BaseSpec->getType())
.getUnqualifiedType();
// C++ [temp.dep]p3:
// In the definition of a class template or a member of a class template,
// if a base class of the class template depends on a template-parameter,
// the base class scope is not examined during unqualified name lookup
// either at the point of definition of the class template or member or
// during an instantiation of the class tem- plate or member.
if (BaseType->isDependentType())
continue;
// Determine whether we need to visit this base class at all,
// updating the count of subobjects appropriately.
std::pair<bool, unsigned>& Subobjects = ClassSubobjects[BaseType];
bool VisitBase = true;
bool SetVirtual = false;
if (BaseSpec->isVirtual()) {
VisitBase = !Subobjects.first;
Subobjects.first = true;
if (isDetectingVirtual() && DetectedVirtual == 0) {
// If this is the first virtual we find, remember it. If it turns out
// there is no base path here, we'll reset it later.
DetectedVirtual = BaseType->getAs<RecordType>();
SetVirtual = true;
}
} else
++Subobjects.second;
if (isRecordingPaths()) {
// Add this base specifier to the current path.
CXXBasePathElement Element;
Element.Base = &*BaseSpec;
Element.Class = Record;
if (BaseSpec->isVirtual())
Element.SubobjectNumber = 0;
else
Element.SubobjectNumber = Subobjects.second;
ScratchPath.push_back(Element);
// Calculate the "top-down" access to this base class.
// The spec actually describes this bottom-up, but top-down is
// equivalent because the definition works out as follows:
// 1. Write down the access along each step in the inheritance
// chain, followed by the access of the decl itself.
// For example, in
// class A { public: int foo; };
// class B : protected A {};
// class C : public B {};
// class D : private C {};
// we would write:
// private public protected public
// 2. If 'private' appears anywhere except far-left, access is denied.
// 3. Otherwise, overall access is determined by the most restrictive
// access in the sequence.
if (IsFirstStep)
ScratchPath.Access = BaseSpec->getAccessSpecifier();
else
ScratchPath.Access = CXXRecordDecl::MergeAccess(AccessToHere,
BaseSpec->getAccessSpecifier());
}
// Track whether there's a path involving this specific base.
bool FoundPathThroughBase = false;
if (BaseMatches(BaseSpec, ScratchPath, UserData)) {
// We've found a path that terminates at this base.
FoundPath = FoundPathThroughBase = true;
if (isRecordingPaths()) {
// We have a path. Make a copy of it before moving on.
Paths.push_back(ScratchPath);
} else if (!isFindingAmbiguities()) {
// We found a path and we don't care about ambiguities;
// return immediately.
return FoundPath;
}
} else if (VisitBase) {
CXXRecordDecl *BaseRecord
= cast<CXXRecordDecl>(BaseSpec->getType()->castAs<RecordType>()
->getDecl());
if (lookupInBases(Context, BaseRecord, BaseMatches, UserData)) {
// C++ [class.member.lookup]p2:
// A member name f in one sub-object B hides a member name f in
// a sub-object A if A is a base class sub-object of B. Any
// declarations that are so hidden are eliminated from
// consideration.
// There is a path to a base class that meets the criteria. If we're
// not collecting paths or finding ambiguities, we're done.
FoundPath = FoundPathThroughBase = true;
if (!isFindingAmbiguities())
return FoundPath;
}
}
// Pop this base specifier off the current path (if we're
// collecting paths).
if (isRecordingPaths()) {
ScratchPath.pop_back();
}
// If we set a virtual earlier, and this isn't a path, forget it again.
if (SetVirtual && !FoundPathThroughBase) {
DetectedVirtual = 0;
}
}
// Reset the scratch path access.
ScratchPath.Access = AccessToHere;
return FoundPath;
}
