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//===- DeclContextInternals.h - DeclContext Representation ------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file defines the data structures used in the implementation
// of DeclContext.
#include "clang/AST/Decl.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclarationName.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/PointerUnion.h"
#include "llvm/ADT/SmallVector.h"
#include <algorithm>
#include <cassert>
namespace clang {
class DependentDiagnostic;
/// \brief An array of decls optimized for the common case of only containing
/// one entry.
struct StoredDeclsList {
/// \brief When in vector form, this is what the Data pointer points to.
using DeclsTy = SmallVector<NamedDecl *, 4>;
/// \brief A collection of declarations, with a flag to indicate if we have
/// further external declarations.
using DeclsAndHasExternalTy = llvm::PointerIntPair<DeclsTy *, 1, bool>;
/// \brief The stored data, which will be either a pointer to a NamedDecl,
/// or a pointer to a vector with a flag to indicate if there are further
/// external declarations.
llvm::PointerUnion<NamedDecl *, DeclsAndHasExternalTy> Data;
StoredDeclsList() = default;
StoredDeclsList(StoredDeclsList &&RHS) : Data(RHS.Data) {
RHS.Data = (NamedDecl *)nullptr;
~StoredDeclsList() {
// If this is a vector-form, free the vector.
if (DeclsTy *Vector = getAsVector())
delete Vector;
StoredDeclsList &operator=(StoredDeclsList &&RHS) {
if (DeclsTy *Vector = getAsVector())
delete Vector;
Data = RHS.Data;
RHS.Data = (NamedDecl *)nullptr;
return *this;
bool isNull() const { return Data.isNull(); }
NamedDecl *getAsDecl() const {
return Data.dyn_cast<NamedDecl *>();
DeclsAndHasExternalTy getAsVectorAndHasExternal() const {
return Data.dyn_cast<DeclsAndHasExternalTy>();
DeclsTy *getAsVector() const {
return getAsVectorAndHasExternal().getPointer();
bool hasExternalDecls() const {
return getAsVectorAndHasExternal().getInt();
void setHasExternalDecls() {
if (DeclsTy *Vec = getAsVector())
Data = DeclsAndHasExternalTy(Vec, true);
else {
DeclsTy *VT = new DeclsTy();
if (NamedDecl *OldD = getAsDecl())
Data = DeclsAndHasExternalTy(VT, true);
void setOnlyValue(NamedDecl *ND) {
assert(!getAsVector() && "Not inline");
Data = ND;
// Make sure that Data is a plain NamedDecl* so we can use its address
// at getLookupResult.
assert(*(NamedDecl **)&Data == ND &&
"PointerUnion mangles the NamedDecl pointer!");
void remove(NamedDecl *D) {
assert(!isNull() && "removing from empty list");
if (NamedDecl *Singleton = getAsDecl()) {
assert(Singleton == D && "list is different singleton");
Data = (NamedDecl *)nullptr;
DeclsTy &Vec = *getAsVector();
DeclsTy::iterator I = std::find(Vec.begin(), Vec.end(), D);
assert(I != Vec.end() && "list does not contain decl");
assert(std::find(Vec.begin(), Vec.end(), D)
== Vec.end() && "list still contains decl");
/// \brief Remove any declarations which were imported from an external
/// AST source.
void removeExternalDecls() {
if (isNull()) {
// Nothing to do.
} else if (NamedDecl *Singleton = getAsDecl()) {
if (Singleton->isFromASTFile())
*this = StoredDeclsList();
} else {
DeclsTy &Vec = *getAsVector();
Vec.erase(std::remove_if(Vec.begin(), Vec.end(),
[](Decl *D) { return D->isFromASTFile(); }),
// Don't have any external decls any more.
Data = DeclsAndHasExternalTy(&Vec, false);
/// getLookupResult - Return an array of all the decls that this list
/// represents.
DeclContext::lookup_result getLookupResult() {
if (isNull())
return DeclContext::lookup_result();
// If we have a single NamedDecl, return it.
if (NamedDecl *ND = getAsDecl()) {
assert(!isNull() && "Empty list isn't allowed");
// Data is a raw pointer to a NamedDecl*, return it.
return DeclContext::lookup_result(ND);
assert(getAsVector() && "Must have a vector at this point");
DeclsTy &Vector = *getAsVector();
// Otherwise, we have a range result.
return DeclContext::lookup_result(Vector);
/// HandleRedeclaration - If this is a redeclaration of an existing decl,
/// replace the old one with D and return true. Otherwise return false.
bool HandleRedeclaration(NamedDecl *D, bool IsKnownNewer) {
// Most decls only have one entry in their list, special case it.
if (NamedDecl *OldD = getAsDecl()) {
if (!D->declarationReplaces(OldD, IsKnownNewer))
return false;
return true;
// Determine if this declaration is actually a redeclaration.
DeclsTy &Vec = *getAsVector();
for (DeclsTy::iterator OD = Vec.begin(), ODEnd = Vec.end();
OD != ODEnd; ++OD) {
NamedDecl *OldD = *OD;
if (D->declarationReplaces(OldD, IsKnownNewer)) {
*OD = D;
return true;
return false;
/// AddSubsequentDecl - This is called on the second and later decl when it is
/// not a redeclaration to merge it into the appropriate place in our list.
void AddSubsequentDecl(NamedDecl *D) {
assert(!isNull() && "don't AddSubsequentDecl when we have no decls");
// If this is the second decl added to the list, convert this to vector
// form.
if (NamedDecl *OldD = getAsDecl()) {
DeclsTy *VT = new DeclsTy();
Data = DeclsAndHasExternalTy(VT, false);
DeclsTy &Vec = *getAsVector();
// Using directives end up in a special entry which contains only
// other using directives, so all this logic is wasted for them.
// But avoiding the logic wastes time in the far-more-common case
// that we're *not* adding a new using directive.
// Tag declarations always go at the end of the list so that an
// iterator which points at the first tag will start a span of
// decls that only contains tags.
if (D->hasTagIdentifierNamespace())
// Resolved using declarations go at the front of the list so that
// they won't show up in other lookup results. Unresolved using
// declarations (which are always in IDNS_Using | IDNS_Ordinary)
// follow that so that the using declarations will be contiguous.
else if (D->getIdentifierNamespace() & Decl::IDNS_Using) {
DeclsTy::iterator I = Vec.begin();
if (D->getIdentifierNamespace() != Decl::IDNS_Using) {
while (I != Vec.end() &&
(*I)->getIdentifierNamespace() == Decl::IDNS_Using)
Vec.insert(I, D);
// All other declarations go at the end of the list, but before any
// tag declarations. But we can be clever about tag declarations
// because there can only ever be one in a scope.
} else if (!Vec.empty() && Vec.back()->hasTagIdentifierNamespace()) {
NamedDecl *TagD = Vec.back();
Vec.back() = D;
} else
class StoredDeclsMap
: public llvm::SmallDenseMap<DeclarationName, StoredDeclsList, 4> {
static void DestroyAll(StoredDeclsMap *Map, bool Dependent);
friend class ASTContext; // walks the chain deleting these
friend class DeclContext;
llvm::PointerIntPair<StoredDeclsMap*, 1> Previous;
class DependentStoredDeclsMap : public StoredDeclsMap {
DependentStoredDeclsMap() = default;
friend class DeclContext; // iterates over diagnostics
friend class DependentDiagnostic;
DependentDiagnostic *FirstDiagnostic = nullptr;
} // namespace clang