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//===---- SemaInherit.cpp - C++ Inheritance ---------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file provides Sema routines for C++ inheritance semantics,
// including searching the inheritance hierarchy and (eventually)
// access checking.
//
//===----------------------------------------------------------------------===//
#include "Sema.h"
#include "SemaInherit.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/Type.h"
#include "clang/AST/TypeOrdering.h"
#include "clang/Basic/Diagnostic.h"
#include <memory>
#include <set>
#include <string>
using namespace clang;
/// isAmbiguous - Determines whether the set of paths provided is
/// ambiguous, i.e., there are two or more paths that refer to
/// different base class subobjects of the same type. BaseType must be
/// an unqualified, canonical class type.
bool BasePaths::isAmbiguous(QualType BaseType) {
assert(BaseType->isCanonical() && "Base type must be the canonical type");
assert(BaseType.getCVRQualifiers() == 0 && "Base type must be unqualified");
std::pair<bool, unsigned>& Subobjects = ClassSubobjects[BaseType];
return Subobjects.second + (Subobjects.first? 1 : 0) > 1;
}
/// clear - Clear out all prior path information.
void BasePaths::clear() {
Paths.clear();
ClassSubobjects.clear();
ScratchPath.clear();
DetectedVirtual = 0;
}
/// IsDerivedFrom - Determine whether the type Derived is derived from
/// the type Base, ignoring qualifiers on Base and Derived. This
/// routine does not assess whether an actual conversion from a
/// Derived* to a Base* is legal, because it does not account for
/// ambiguous conversions or conversions to private/protected bases.
bool Sema::IsDerivedFrom(QualType Derived, QualType Base) {
BasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/false,
/*DetectVirtual=*/false);
return IsDerivedFrom(Derived, Base, Paths);
}
/// IsDerivedFrom - Determine whether the type Derived is derived from
/// the type Base, ignoring qualifiers on Base and Derived. This
/// routine does not assess whether an actual conversion from a
/// Derived* to a Base* is legal, because it does not account for
/// ambiguous conversions or conversions to private/protected
/// bases. This routine will use Paths to determine if there are
/// ambiguous paths (if @c Paths.isFindingAmbiguities()) and record
/// information about all of the paths (if @c Paths.isRecordingPaths()).
bool Sema::IsDerivedFrom(QualType Derived, QualType Base, BasePaths &Paths) {
bool FoundPath = false;
Derived = Context.getCanonicalType(Derived).getUnqualifiedType();
Base = Context.getCanonicalType(Base).getUnqualifiedType();
if (!Derived->isRecordType() || !Base->isRecordType())
return false;
if (Derived == Base)
return false;
if (const RecordType *DerivedType = Derived->getAsRecordType()) {
const CXXRecordDecl *Decl
= static_cast<const CXXRecordDecl *>(DerivedType->getDecl());
for (CXXRecordDecl::base_class_const_iterator BaseSpec = Decl->bases_begin();
BaseSpec != Decl->bases_end(); ++BaseSpec) {
// Find the record of the base class subobjects for this type.
QualType BaseType = Context.getCanonicalType(BaseSpec->getType());
BaseType = BaseType.getUnqualifiedType();
// Determine whether we need to visit this base class at all,
// updating the count of subobjects appropriately.
std::pair<bool, unsigned>& Subobjects = Paths.ClassSubobjects[BaseType];
bool VisitBase = true;
bool SetVirtual = false;
if (BaseSpec->isVirtual()) {
VisitBase = !Subobjects.first;
Subobjects.first = true;
if (Paths.isDetectingVirtual() && Paths.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.
Paths.DetectedVirtual = static_cast<const CXXRecordType*>(
BaseType->getAsRecordType());
SetVirtual = true;
}
} else
++Subobjects.second;
if (Paths.isRecordingPaths()) {
// Add this base specifier to the current path.
BasePathElement Element;
Element.Base = &*BaseSpec;
if (BaseSpec->isVirtual())
Element.SubobjectNumber = 0;
else
Element.SubobjectNumber = Subobjects.second;
Paths.ScratchPath.push_back(Element);
}
if (Context.getCanonicalType(BaseSpec->getType()) == Base) {
// We've found the base we're looking for.
FoundPath = true;
if (Paths.isRecordingPaths()) {
// We have a path. Make a copy of it before moving on.
Paths.Paths.push_back(Paths.ScratchPath);
} else if (!Paths.isFindingAmbiguities()) {
// We found a path and we don't care about ambiguities;
// return immediately.
return FoundPath;
}
} else if (VisitBase && IsDerivedFrom(BaseSpec->getType(), Base, Paths)) {
// There is a path to the base we want. If we're not
// collecting paths or finding ambiguities, we're done.
FoundPath = true;
if (!Paths.isFindingAmbiguities())
return FoundPath;
}
// Pop this base specifier off the current path (if we're
// collecting paths).
if (Paths.isRecordingPaths())
Paths.ScratchPath.pop_back();
// If we set a virtual earlier, and this isn't a path, forget it again.
if (SetVirtual && !FoundPath) {
Paths.DetectedVirtual = 0;
}
}
}
return FoundPath;
}
/// CheckDerivedToBaseConversion - Check whether the Derived-to-Base
/// conversion (where Derived and Base are class types) is
/// well-formed, meaning that the conversion is unambiguous (and
/// FIXME: that all of the base classes are accessible). Returns true
/// and emits a diagnostic if the code is ill-formed, returns false
/// otherwise. Loc is the location where this routine should point to
/// if there is an error, and Range is the source range to highlight
/// if there is an error.
bool
Sema::CheckDerivedToBaseConversion(QualType Derived, QualType Base,
SourceLocation Loc, SourceRange Range) {
// First, determine whether the path from Derived to Base is
// ambiguous. This is slightly more expensive than checking whether
// the Derived to Base conversion exists, because here we need to
// explore multiple paths to determine if there is an ambiguity.
BasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/false,
/*DetectVirtual=*/false);
bool DerivationOkay = IsDerivedFrom(Derived, Base, Paths);
assert(DerivationOkay && "Can only be used with a derived-to-base conversion");
if (!DerivationOkay)
return true;
if (!Paths.isAmbiguous(Context.getCanonicalType(Base).getUnqualifiedType()))
return false;
// We know that the derived-to-base conversion is ambiguous, and
// we're going to produce a diagnostic. Perform the derived-to-base
// search just one more time to compute all of the possible paths so
// that we can print them out. This is more expensive than any of
// the previous derived-to-base checks we've done, but at this point
// performance isn't as much of an issue.
Paths.clear();
Paths.setRecordingPaths(true);
bool StillOkay = IsDerivedFrom(Derived, Base, Paths);
assert(StillOkay && "Can only be used with a derived-to-base conversion");
if (!StillOkay)
return true;
// Build up a textual representation of the ambiguous paths, e.g.,
// D -> B -> A, that will be used to illustrate the ambiguous
// conversions in the diagnostic. We only print one of the paths
// to each base class subobject.
std::string PathDisplayStr;
std::set<unsigned> DisplayedPaths;
for (BasePaths::paths_iterator Path = Paths.begin();
Path != Paths.end(); ++Path) {
if (DisplayedPaths.insert(Path->back().SubobjectNumber).second) {
// We haven't displayed a path to this particular base
// class subobject yet.
PathDisplayStr += "\n ";
PathDisplayStr += Derived.getAsString();
for (BasePath::const_iterator Element = Path->begin();
Element != Path->end(); ++Element)
PathDisplayStr += " -> " + Element->Base->getType().getAsString();
}
}
Diag(Loc, diag::err_ambiguous_derived_to_base_conv)
<< Derived << Base << PathDisplayStr << Range;
return true;
}
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