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//===--------------------- SemaLookup.cpp - Name Lookup ------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file implements name lookup for C, C++, Objective-C, and
// Objective-C++.
#include "clang/AST/ASTContext.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclLookups.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/FileManager.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Lex/HeaderSearch.h"
#include "clang/Lex/ModuleLoader.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/Overload.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/Sema.h"
#include "clang/Sema/SemaInternal.h"
#include "clang/Sema/TemplateDeduction.h"
#include "clang/Sema/TypoCorrection.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/ADT/edit_distance.h"
#include "llvm/Support/ErrorHandling.h"
#include <algorithm>
#include <iterator>
#include <list>
#include <set>
#include <utility>
#include <vector>
#include ""
using namespace clang;
using namespace sema;
namespace {
class UnqualUsingEntry {
const DeclContext *Nominated;
const DeclContext *CommonAncestor;
UnqualUsingEntry(const DeclContext *Nominated,
const DeclContext *CommonAncestor)
: Nominated(Nominated), CommonAncestor(CommonAncestor) {
const DeclContext *getCommonAncestor() const {
return CommonAncestor;
const DeclContext *getNominatedNamespace() const {
return Nominated;
// Sort by the pointer value of the common ancestor.
struct Comparator {
bool operator()(const UnqualUsingEntry &L, const UnqualUsingEntry &R) {
return L.getCommonAncestor() < R.getCommonAncestor();
bool operator()(const UnqualUsingEntry &E, const DeclContext *DC) {
return E.getCommonAncestor() < DC;
bool operator()(const DeclContext *DC, const UnqualUsingEntry &E) {
return DC < E.getCommonAncestor();
/// A collection of using directives, as used by C++ unqualified
/// lookup.
class UnqualUsingDirectiveSet {
Sema &SemaRef;
typedef SmallVector<UnqualUsingEntry, 8> ListTy;
ListTy list;
llvm::SmallPtrSet<DeclContext*, 8> visited;
UnqualUsingDirectiveSet(Sema &SemaRef) : SemaRef(SemaRef) {}
void visitScopeChain(Scope *S, Scope *InnermostFileScope) {
// C++ [namespace.udir]p1:
// During unqualified name lookup, the names appear as if they
// were declared in the nearest enclosing namespace which contains
// both the using-directive and the nominated namespace.
DeclContext *InnermostFileDC = InnermostFileScope->getEntity();
assert(InnermostFileDC && InnermostFileDC->isFileContext());
for (; S; S = S->getParent()) {
// C++ [namespace.udir]p1:
// A using-directive shall not appear in class scope, but may
// appear in namespace scope or in block scope.
DeclContext *Ctx = S->getEntity();
if (Ctx && Ctx->isFileContext()) {
visit(Ctx, Ctx);
} else if (!Ctx || Ctx->isFunctionOrMethod()) {
for (auto *I : S->using_directives())
if (SemaRef.isVisible(I))
visit(I, InnermostFileDC);
// Visits a context and collect all of its using directives
// recursively. Treats all using directives as if they were
// declared in the context.
// A given context is only every visited once, so it is important
// that contexts be visited from the inside out in order to get
// the effective DCs right.
void visit(DeclContext *DC, DeclContext *EffectiveDC) {
if (!visited.insert(DC).second)
addUsingDirectives(DC, EffectiveDC);
// Visits a using directive and collects all of its using
// directives recursively. Treats all using directives as if they
// were declared in the effective DC.
void visit(UsingDirectiveDecl *UD, DeclContext *EffectiveDC) {
DeclContext *NS = UD->getNominatedNamespace();
if (!visited.insert(NS).second)
addUsingDirective(UD, EffectiveDC);
addUsingDirectives(NS, EffectiveDC);
// Adds all the using directives in a context (and those nominated
// by its using directives, transitively) as if they appeared in
// the given effective context.
void addUsingDirectives(DeclContext *DC, DeclContext *EffectiveDC) {
SmallVector<DeclContext*, 4> queue;
while (true) {
for (auto UD : DC->using_directives()) {
DeclContext *NS = UD->getNominatedNamespace();
if (SemaRef.isVisible(UD) && visited.insert(NS).second) {
addUsingDirective(UD, EffectiveDC);
if (queue.empty())
DC = queue.pop_back_val();
// Add a using directive as if it had been declared in the given
// context. This helps implement C++ [namespace.udir]p3:
// The using-directive is transitive: if a scope contains a
// using-directive that nominates a second namespace that itself
// contains using-directives, the effect is as if the
// using-directives from the second namespace also appeared in
// the first.
void addUsingDirective(UsingDirectiveDecl *UD, DeclContext *EffectiveDC) {
// Find the common ancestor between the effective context and
// the nominated namespace.
DeclContext *Common = UD->getNominatedNamespace();
while (!Common->Encloses(EffectiveDC))
Common = Common->getParent();
Common = Common->getPrimaryContext();
list.push_back(UnqualUsingEntry(UD->getNominatedNamespace(), Common));
void done() { llvm::sort(list, UnqualUsingEntry::Comparator()); }
typedef ListTy::const_iterator const_iterator;
const_iterator begin() const { return list.begin(); }
const_iterator end() const { return list.end(); }
getNamespacesFor(DeclContext *DC) const {
return llvm::make_range(std::equal_range(begin(), end(),
} // end anonymous namespace
// Retrieve the set of identifier namespaces that correspond to a
// specific kind of name lookup.
static inline unsigned getIDNS(Sema::LookupNameKind NameKind,
bool CPlusPlus,
bool Redeclaration) {
unsigned IDNS = 0;
switch (NameKind) {
case Sema::LookupObjCImplicitSelfParam:
case Sema::LookupOrdinaryName:
case Sema::LookupRedeclarationWithLinkage:
case Sema::LookupLocalFriendName:
case Sema::LookupDestructorName:
IDNS = Decl::IDNS_Ordinary;
if (CPlusPlus) {
IDNS |= Decl::IDNS_Tag | Decl::IDNS_Member | Decl::IDNS_Namespace;
if (Redeclaration)
IDNS |= Decl::IDNS_TagFriend | Decl::IDNS_OrdinaryFriend;
if (Redeclaration)
IDNS |= Decl::IDNS_LocalExtern;
case Sema::LookupOperatorName:
// Operator lookup is its own crazy thing; it is not the same
// as (e.g.) looking up an operator name for redeclaration.
assert(!Redeclaration && "cannot do redeclaration operator lookup");
IDNS = Decl::IDNS_NonMemberOperator;
case Sema::LookupTagName:
if (CPlusPlus) {
IDNS = Decl::IDNS_Type;
// When looking for a redeclaration of a tag name, we add:
// 1) TagFriend to find undeclared friend decls
// 2) Namespace because they can't "overload" with tag decls.
// 3) Tag because it includes class templates, which can't
// "overload" with tag decls.
if (Redeclaration)
IDNS |= Decl::IDNS_Tag | Decl::IDNS_TagFriend | Decl::IDNS_Namespace;
} else {
IDNS = Decl::IDNS_Tag;
case Sema::LookupLabel:
IDNS = Decl::IDNS_Label;
case Sema::LookupMemberName:
IDNS = Decl::IDNS_Member;
if (CPlusPlus)
IDNS |= Decl::IDNS_Tag | Decl::IDNS_Ordinary;
case Sema::LookupNestedNameSpecifierName:
IDNS = Decl::IDNS_Type | Decl::IDNS_Namespace;
case Sema::LookupNamespaceName:
IDNS = Decl::IDNS_Namespace;
case Sema::LookupUsingDeclName:
assert(Redeclaration && "should only be used for redecl lookup");
IDNS = Decl::IDNS_Ordinary | Decl::IDNS_Tag | Decl::IDNS_Member |
Decl::IDNS_Using | Decl::IDNS_TagFriend | Decl::IDNS_OrdinaryFriend |
case Sema::LookupObjCProtocolName:
IDNS = Decl::IDNS_ObjCProtocol;
case Sema::LookupOMPReductionName:
IDNS = Decl::IDNS_OMPReduction;
case Sema::LookupOMPMapperName:
IDNS = Decl::IDNS_OMPMapper;
case Sema::LookupAnyName:
IDNS = Decl::IDNS_Ordinary | Decl::IDNS_Tag | Decl::IDNS_Member
| Decl::IDNS_Using | Decl::IDNS_Namespace | Decl::IDNS_ObjCProtocol
| Decl::IDNS_Type;
return IDNS;
void LookupResult::configure() {
IDNS = getIDNS(LookupKind, getSema().getLangOpts().CPlusPlus,
// If we're looking for one of the allocation or deallocation
// operators, make sure that the implicitly-declared new and delete
// operators can be found.
switch (NameInfo.getName().getCXXOverloadedOperator()) {
case OO_New:
case OO_Delete:
case OO_Array_New:
case OO_Array_Delete:
// Compiler builtins are always visible, regardless of where they end
// up being declared.
if (IdentifierInfo *Id = NameInfo.getName().getAsIdentifierInfo()) {
if (unsigned BuiltinID = Id->getBuiltinID()) {
if (!getSema().Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID))
AllowHidden = true;
bool LookupResult::checkDebugAssumptions() const {
// This function is never called by NDEBUG builds.
assert(ResultKind != NotFound || Decls.size() == 0);
assert(ResultKind != Found || Decls.size() == 1);
assert(ResultKind != FoundOverloaded || Decls.size() > 1 ||
(Decls.size() == 1 &&
assert(ResultKind != FoundUnresolvedValue || checkUnresolved());
assert(ResultKind != Ambiguous || Decls.size() > 1 ||
(Decls.size() == 1 && (Ambiguity == AmbiguousBaseSubobjects ||
Ambiguity == AmbiguousBaseSubobjectTypes)));
assert((Paths != nullptr) == (ResultKind == Ambiguous &&
(Ambiguity == AmbiguousBaseSubobjectTypes ||
Ambiguity == AmbiguousBaseSubobjects)));
return true;
// Necessary because CXXBasePaths is not complete in Sema.h
void LookupResult::deletePaths(CXXBasePaths *Paths) {
delete Paths;
/// Get a representative context for a declaration such that two declarations
/// will have the same context if they were found within the same scope.
static DeclContext *getContextForScopeMatching(Decl *D) {
// For function-local declarations, use that function as the context. This
// doesn't account for scopes within the function; the caller must deal with
// those.
DeclContext *DC = D->getLexicalDeclContext();
if (DC->isFunctionOrMethod())
return DC;
// Otherwise, look at the semantic context of the declaration. The
// declaration must have been found there.
return D->getDeclContext()->getRedeclContext();
/// Determine whether \p D is a better lookup result than \p Existing,
/// given that they declare the same entity.
static bool isPreferredLookupResult(Sema &S, Sema::LookupNameKind Kind,
NamedDecl *D, NamedDecl *Existing) {
// When looking up redeclarations of a using declaration, prefer a using
// shadow declaration over any other declaration of the same entity.
if (Kind == Sema::LookupUsingDeclName && isa<UsingShadowDecl>(D) &&
return true;
auto *DUnderlying = D->getUnderlyingDecl();
auto *EUnderlying = Existing->getUnderlyingDecl();
// If they have different underlying declarations, prefer a typedef over the
// original type (this happens when two type declarations denote the same
// type), per a generous reading of C++ [dcl.typedef]p3 and p4. The typedef
// might carry additional semantic information, such as an alignment override.
// However, per C++ [dcl.typedef]p5, when looking up a tag name, prefer a tag
// declaration over a typedef. Also prefer a tag over a typedef for
// destructor name lookup because in some contexts we only accept a
// class-name in a destructor declaration.
if (DUnderlying->getCanonicalDecl() != EUnderlying->getCanonicalDecl()) {
assert(isa<TypeDecl>(DUnderlying) && isa<TypeDecl>(EUnderlying));
bool HaveTag = isa<TagDecl>(EUnderlying);
bool WantTag =
Kind == Sema::LookupTagName || Kind == Sema::LookupDestructorName;
return HaveTag != WantTag;
// Pick the function with more default arguments.
// FIXME: In the presence of ambiguous default arguments, we should keep both,
// so we can diagnose the ambiguity if the default argument is needed.
// See C++ []p3.
if (auto *DFD = dyn_cast<FunctionDecl>(DUnderlying)) {
auto *EFD = cast<FunctionDecl>(EUnderlying);
unsigned DMin = DFD->getMinRequiredArguments();
unsigned EMin = EFD->getMinRequiredArguments();
// If D has more default arguments, it is preferred.
if (DMin != EMin)
return DMin < EMin;
// FIXME: When we track visibility for default function arguments, check
// that we pick the declaration with more visible default arguments.
// Pick the template with more default template arguments.
if (auto *DTD = dyn_cast<TemplateDecl>(DUnderlying)) {
auto *ETD = cast<TemplateDecl>(EUnderlying);
unsigned DMin = DTD->getTemplateParameters()->getMinRequiredArguments();
unsigned EMin = ETD->getTemplateParameters()->getMinRequiredArguments();
// If D has more default arguments, it is preferred. Note that default
// arguments (and their visibility) is monotonically increasing across the
// redeclaration chain, so this is a quick proxy for "is more recent".
if (DMin != EMin)
return DMin < EMin;
// If D has more *visible* default arguments, it is preferred. Note, an
// earlier default argument being visible does not imply that a later
// default argument is visible, so we can't just check the first one.
for (unsigned I = DMin, N = DTD->getTemplateParameters()->size();
I != N; ++I) {
if (!S.hasVisibleDefaultArgument(
ETD->getTemplateParameters()->getParam(I)) &&
return true;
// VarDecl can have incomplete array types, prefer the one with more complete
// array type.
if (VarDecl *DVD = dyn_cast<VarDecl>(DUnderlying)) {
VarDecl *EVD = cast<VarDecl>(EUnderlying);
if (EVD->getType()->isIncompleteType() &&
!DVD->getType()->isIncompleteType()) {
// Prefer the decl with a more complete type if visible.
return S.isVisible(DVD);
return false; // Avoid picking up a newer decl, just because it was newer.
// For most kinds of declaration, it doesn't really matter which one we pick.
if (!isa<FunctionDecl>(DUnderlying) && !isa<VarDecl>(DUnderlying)) {
// If the existing declaration is hidden, prefer the new one. Otherwise,
// keep what we've got.
return !S.isVisible(Existing);
// Pick the newer declaration; it might have a more precise type.
for (Decl *Prev = DUnderlying->getPreviousDecl(); Prev;
Prev = Prev->getPreviousDecl())
if (Prev == EUnderlying)
return true;
return false;
/// Determine whether \p D can hide a tag declaration.
static bool canHideTag(NamedDecl *D) {
// C++ [basic.scope.declarative]p4:
// Given a set of declarations in a single declarative region [...]
// exactly one declaration shall declare a class name or enumeration name
// that is not a typedef name and the other declarations shall all refer to
// the same variable, non-static data member, or enumerator, or all refer
// to functions and function templates; in this case the class name or
// enumeration name is hidden.
// C++ [basic.scope.hiding]p2:
// A class name or enumeration name can be hidden by the name of a
// variable, data member, function, or enumerator declared in the same
// scope.
// An UnresolvedUsingValueDecl always instantiates to one of these.
D = D->getUnderlyingDecl();
return isa<VarDecl>(D) || isa<EnumConstantDecl>(D) || isa<FunctionDecl>(D) ||
isa<FunctionTemplateDecl>(D) || isa<FieldDecl>(D) ||
/// Resolves the result kind of this lookup.
void LookupResult::resolveKind() {
unsigned N = Decls.size();
// Fast case: no possible ambiguity.
if (N == 0) {
assert(ResultKind == NotFound ||
ResultKind == NotFoundInCurrentInstantiation);
// If there's a single decl, we need to examine it to decide what
// kind of lookup this is.
if (N == 1) {
NamedDecl *D = (*Decls.begin())->getUnderlyingDecl();
if (isa<FunctionTemplateDecl>(D))
ResultKind = FoundOverloaded;
else if (isa<UnresolvedUsingValueDecl>(D))
ResultKind = FoundUnresolvedValue;
// Don't do any extra resolution if we've already resolved as ambiguous.
if (ResultKind == Ambiguous) return;
llvm::SmallDenseMap<NamedDecl*, unsigned, 16> Unique;
llvm::SmallDenseMap<QualType, unsigned, 16> UniqueTypes;
bool Ambiguous = false;
bool HasTag = false, HasFunction = false;
bool HasFunctionTemplate = false, HasUnresolved = false;
NamedDecl *HasNonFunction = nullptr;
llvm::SmallVector<NamedDecl*, 4> EquivalentNonFunctions;
unsigned UniqueTagIndex = 0;
unsigned I = 0;
while (I < N) {
NamedDecl *D = Decls[I]->getUnderlyingDecl();
D = cast<NamedDecl>(D->getCanonicalDecl());
// Ignore an invalid declaration unless it's the only one left.
if (D->isInvalidDecl() && !(I == 0 && N == 1)) {
Decls[I] = Decls[--N];
llvm::Optional<unsigned> ExistingI;
// Redeclarations of types via typedef can occur both within a scope
// and, through using declarations and directives, across scopes. There is
// no ambiguity if they all refer to the same type, so unique based on the
// canonical type.
if (TypeDecl *TD = dyn_cast<TypeDecl>(D)) {
QualType T = getSema().Context.getTypeDeclType(TD);
auto UniqueResult = UniqueTypes.insert(
std::make_pair(getSema().Context.getCanonicalType(T), I));
if (!UniqueResult.second) {
// The type is not unique.
ExistingI = UniqueResult.first->second;
// For non-type declarations, check for a prior lookup result naming this
// canonical declaration.
if (!ExistingI) {
auto UniqueResult = Unique.insert(std::make_pair(D, I));
if (!UniqueResult.second) {
// We've seen this entity before.
ExistingI = UniqueResult.first->second;
if (ExistingI) {
// This is not a unique lookup result. Pick one of the results and
// discard the other.
if (isPreferredLookupResult(getSema(), getLookupKind(), Decls[I],
Decls[*ExistingI] = Decls[I];
Decls[I] = Decls[--N];
// Otherwise, do some decl type analysis and then continue.
if (isa<UnresolvedUsingValueDecl>(D)) {
HasUnresolved = true;
} else if (isa<TagDecl>(D)) {
if (HasTag)
Ambiguous = true;
UniqueTagIndex = I;
HasTag = true;
} else if (isa<FunctionTemplateDecl>(D)) {
HasFunction = true;
HasFunctionTemplate = true;
} else if (isa<FunctionDecl>(D)) {
HasFunction = true;
} else {
if (HasNonFunction) {
// If we're about to create an ambiguity between two declarations that
// are equivalent, but one is an internal linkage declaration from one
// module and the other is an internal linkage declaration from another
// module, just skip it.
if (getSema().isEquivalentInternalLinkageDeclaration(HasNonFunction,
D)) {
Decls[I] = Decls[--N];
Ambiguous = true;
HasNonFunction = D;
// C++ [basic.scope.hiding]p2:
// A class name or enumeration name can be hidden by the name of
// an object, function, or enumerator declared in the same
// scope. If a class or enumeration name and an object, function,
// or enumerator are declared in the same scope (in any order)
// with the same name, the class or enumeration name is hidden
// wherever the object, function, or enumerator name is visible.
// But it's still an error if there are distinct tag types found,
// even if they're not visible. (ref?)
if (N > 1 && HideTags && HasTag && !Ambiguous &&
(HasFunction || HasNonFunction || HasUnresolved)) {
NamedDecl *OtherDecl = Decls[UniqueTagIndex ? 0 : N - 1];
if (isa<TagDecl>(Decls[UniqueTagIndex]->getUnderlyingDecl()) &&
getContextForScopeMatching(OtherDecl)) &&
Decls[UniqueTagIndex] = Decls[--N];
Ambiguous = true;
// FIXME: This diagnostic should really be delayed until we're done with
// the lookup result, in case the ambiguity is resolved by the caller.
if (!EquivalentNonFunctions.empty() && !Ambiguous)
getNameLoc(), HasNonFunction, EquivalentNonFunctions);
if (HasNonFunction && (HasFunction || HasUnresolved))
Ambiguous = true;
if (Ambiguous)
else if (HasUnresolved)
ResultKind = LookupResult::FoundUnresolvedValue;
else if (N > 1 || HasFunctionTemplate)
ResultKind = LookupResult::FoundOverloaded;
ResultKind = LookupResult::Found;
void LookupResult::addDeclsFromBasePaths(const CXXBasePaths &P) {
CXXBasePaths::const_paths_iterator I, E;
for (I = P.begin(), E = P.end(); I != E; ++I)
for (DeclContext::lookup_iterator DI = I->Decls, DE = DI.end(); DI != DE;
void LookupResult::setAmbiguousBaseSubobjects(CXXBasePaths &P) {
Paths = new CXXBasePaths;
void LookupResult::setAmbiguousBaseSubobjectTypes(CXXBasePaths &P) {
Paths = new CXXBasePaths;
void LookupResult::print(raw_ostream &Out) {
Out << Decls.size() << " result(s)";
if (isAmbiguous()) Out << ", ambiguous";
if (Paths) Out << ", base paths present";
for (iterator I = begin(), E = end(); I != E; ++I) {
Out << "\n";
(*I)->print(Out, 2);
LLVM_DUMP_METHOD void LookupResult::dump() {
llvm::errs() << "lookup results for " << getLookupName().getAsString()
<< ":\n";
for (NamedDecl *D : *this)
/// Diagnose a missing builtin type.
static QualType diagOpenCLBuiltinTypeError(Sema &S, llvm::StringRef TypeClass,
llvm::StringRef Name) {
S.Diag(SourceLocation(), diag::err_opencl_type_not_found)
<< TypeClass << Name;
return S.Context.VoidTy;
/// Lookup an OpenCL enum type.
static QualType getOpenCLEnumType(Sema &S, llvm::StringRef Name) {
LookupResult Result(S, &S.Context.Idents.get(Name), SourceLocation(),
S.LookupName(Result, S.TUScope);
if (Result.empty())
return diagOpenCLBuiltinTypeError(S, "enum", Name);
EnumDecl *Decl = Result.getAsSingle<EnumDecl>();
if (!Decl)
return diagOpenCLBuiltinTypeError(S, "enum", Name);
return S.Context.getEnumType(Decl);
/// Lookup an OpenCL typedef type.
static QualType getOpenCLTypedefType(Sema &S, llvm::StringRef Name) {
LookupResult Result(S, &S.Context.Idents.get(Name), SourceLocation(),
S.LookupName(Result, S.TUScope);
if (Result.empty())
return diagOpenCLBuiltinTypeError(S, "typedef", Name);
TypedefNameDecl *Decl = Result.getAsSingle<TypedefNameDecl>();
if (!Decl)
return diagOpenCLBuiltinTypeError(S, "typedef", Name);
return S.Context.getTypedefType(Decl);
/// Get the QualType instances of the return type and arguments for an OpenCL
/// builtin function signature.
/// \param S (in) The Sema instance.
/// \param OpenCLBuiltin (in) The signature currently handled.
/// \param GenTypeMaxCnt (out) Maximum number of types contained in a generic
/// type used as return type or as argument.
/// Only meaningful for generic types, otherwise equals 1.
/// \param RetTypes (out) List of the possible return types.
/// \param ArgTypes (out) List of the possible argument types. For each
/// argument, ArgTypes contains QualTypes for the Cartesian product
/// of (vector sizes) x (types) .
static void GetQualTypesForOpenCLBuiltin(
Sema &S, const OpenCLBuiltinStruct &OpenCLBuiltin, unsigned &GenTypeMaxCnt,
SmallVector<QualType, 1> &RetTypes,
SmallVector<SmallVector<QualType, 1>, 5> &ArgTypes) {
// Get the QualType instances of the return types.
unsigned Sig = SignatureTable[OpenCLBuiltin.SigTableIndex];
OCL2Qual(S, TypeTable[Sig], RetTypes);
GenTypeMaxCnt = RetTypes.size();
// Get the QualType instances of the arguments.
// First type is the return type, skip it.
for (unsigned Index = 1; Index < OpenCLBuiltin.NumTypes; Index++) {
SmallVector<QualType, 1> Ty;
OCL2Qual(S, TypeTable[SignatureTable[OpenCLBuiltin.SigTableIndex + Index]],
GenTypeMaxCnt = (Ty.size() > GenTypeMaxCnt) ? Ty.size() : GenTypeMaxCnt;
/// Create a list of the candidate function overloads for an OpenCL builtin
/// function.
/// \param Context (in) The ASTContext instance.
/// \param GenTypeMaxCnt (in) Maximum number of types contained in a generic
/// type used as return type or as argument.
/// Only meaningful for generic types, otherwise equals 1.
/// \param FunctionList (out) List of FunctionTypes.
/// \param RetTypes (in) List of the possible return types.
/// \param ArgTypes (in) List of the possible types for the arguments.
static void GetOpenCLBuiltinFctOverloads(
ASTContext &Context, unsigned GenTypeMaxCnt,
std::vector<QualType> &FunctionList, SmallVector<QualType, 1> &RetTypes,
SmallVector<SmallVector<QualType, 1>, 5> &ArgTypes) {
FunctionProtoType::ExtProtoInfo PI(
Context.getDefaultCallingConvention(false, false, true));
PI.Variadic = false;
// Do not attempt to create any FunctionTypes if there are no return types,
// which happens when a type belongs to a disabled extension.
if (RetTypes.size() == 0)
// Create FunctionTypes for each (gen)type.
for (unsigned IGenType = 0; IGenType < GenTypeMaxCnt; IGenType++) {
SmallVector<QualType, 5> ArgList;
for (unsigned A = 0; A < ArgTypes.size(); A++) {
// Bail out if there is an argument that has no available types.
if (ArgTypes[A].size() == 0)
// Builtins such as "max" have an "sgentype" argument that represents
// the corresponding scalar type of a gentype. The number of gentypes
// must be a multiple of the number of sgentypes.
assert(GenTypeMaxCnt % ArgTypes[A].size() == 0 &&
"argument type count not compatible with gentype type count");
unsigned Idx = IGenType % ArgTypes[A].size();
RetTypes[(RetTypes.size() != 1) ? IGenType : 0], ArgList, PI));
/// When trying to resolve a function name, if isOpenCLBuiltin() returns a
/// non-null <Index, Len> pair, then the name is referencing an OpenCL
/// builtin function. Add all candidate signatures to the LookUpResult.
/// \param S (in) The Sema instance.
/// \param LR (inout) The LookupResult instance.
/// \param II (in) The identifier being resolved.
/// \param FctIndex (in) Starting index in the BuiltinTable.
/// \param Len (in) The signature list has Len elements.
static void InsertOCLBuiltinDeclarationsFromTable(Sema &S, LookupResult &LR,
IdentifierInfo *II,
const unsigned FctIndex,
const unsigned Len) {
// The builtin function declaration uses generic types (gentype).
bool HasGenType = false;
// Maximum number of types contained in a generic type used as return type or
// as argument. Only meaningful for generic types, otherwise equals 1.
unsigned GenTypeMaxCnt;
ASTContext &Context = S.Context;
for (unsigned SignatureIndex = 0; SignatureIndex < Len; SignatureIndex++) {
const OpenCLBuiltinStruct &OpenCLBuiltin =
BuiltinTable[FctIndex + SignatureIndex];
// Ignore this builtin function if it is not available in the currently
// selected language version.
if (!isOpenCLVersionContainedInMask(Context.getLangOpts(),
// Ignore this builtin function if it carries an extension macro that is
// not defined. This indicates that the extension is not supported by the
// target, so the builtin function should not be available.
StringRef Extensions = FunctionExtensionTable[OpenCLBuiltin.Extension];
if (!Extensions.empty()) {
SmallVector<StringRef, 2> ExtVec;
Extensions.split(ExtVec, " ");
bool AllExtensionsDefined = true;
for (StringRef Ext : ExtVec) {
if (!S.getPreprocessor().isMacroDefined(Ext)) {
AllExtensionsDefined = false;
if (!AllExtensionsDefined)
SmallVector<QualType, 1> RetTypes;
SmallVector<SmallVector<QualType, 1>, 5> ArgTypes;
// Obtain QualType lists for the function signature.
GetQualTypesForOpenCLBuiltin(S, OpenCLBuiltin, GenTypeMaxCnt, RetTypes,
if (GenTypeMaxCnt > 1) {
HasGenType = true;
// Create function overload for each type combination.
std::vector<QualType> FunctionList;
GetOpenCLBuiltinFctOverloads(Context, GenTypeMaxCnt, FunctionList, RetTypes,
SourceLocation Loc = LR.getNameLoc();
DeclContext *Parent = Context.getTranslationUnitDecl();
FunctionDecl *NewOpenCLBuiltin;
for (const auto &FTy : FunctionList) {
NewOpenCLBuiltin = FunctionDecl::Create(
Context, Parent, Loc, Loc, II, FTy, /*TInfo=*/nullptr, SC_Extern,
S.getCurFPFeatures().isFPConstrained(), false,
// Create Decl objects for each parameter, adding them to the
// FunctionDecl.
const auto *FP = cast<FunctionProtoType>(FTy);
SmallVector<ParmVarDecl *, 4> ParmList;
for (unsigned IParm = 0, e = FP->getNumParams(); IParm != e; ++IParm) {
ParmVarDecl *Parm = ParmVarDecl::Create(
Context, NewOpenCLBuiltin, SourceLocation(), SourceLocation(),
nullptr, FP->getParamType(IParm), nullptr, SC_None, nullptr);
Parm->setScopeInfo(0, IParm);
// Add function attributes.
if (OpenCLBuiltin.IsPure)
if (OpenCLBuiltin.IsConst)
if (OpenCLBuiltin.IsConv)
if (!S.getLangOpts().OpenCLCPlusPlus)
// If we added overloads, need to resolve the lookup result.
if (Len > 1 || HasGenType)
/// Lookup a builtin function, when name lookup would otherwise
/// fail.
bool Sema::LookupBuiltin(LookupResult &R) {
Sema::LookupNameKind NameKind = R.getLookupKind();
// If we didn't find a use of this identifier, and if the identifier
// corresponds to a compiler builtin, create the decl object for the builtin
// now, injecting it into translation unit scope, and return it.
if (NameKind == Sema::LookupOrdinaryName ||
NameKind == Sema::LookupRedeclarationWithLinkage) {
IdentifierInfo *II = R.getLookupName().getAsIdentifierInfo();
if (II) {
if (getLangOpts().CPlusPlus && NameKind == Sema::LookupOrdinaryName) {
if (II == getASTContext().getMakeIntegerSeqName()) {
return true;
} else if (II == getASTContext().getTypePackElementName()) {
return true;
// Check if this is an OpenCL Builtin, and if so, insert its overloads.
if (getLangOpts().OpenCL && getLangOpts().DeclareOpenCLBuiltins) {
auto Index = isOpenCLBuiltin(II->getName());
if (Index.first) {
InsertOCLBuiltinDeclarationsFromTable(*this, R, II, Index.first - 1,
return true;
// If this is a builtin on this (or all) targets, create the decl.
if (unsigned BuiltinID = II->getBuiltinID()) {
// In C++ and OpenCL (spec v1.2 s6.9.f), we don't have any predefined
// library functions like 'malloc'. Instead, we'll just error.
if ((getLangOpts().CPlusPlus || getLangOpts().OpenCL) &&
return false;
if (NamedDecl *D =
LazilyCreateBuiltin(II, BuiltinID, TUScope,
R.isForRedeclaration(), R.getNameLoc())) {
return true;
return false;
/// Looks up the declaration of "struct objc_super" and
/// saves it for later use in building builtin declaration of
/// objc_msgSendSuper and objc_msgSendSuper_stret.
static void LookupPredefedObjCSuperType(Sema &Sema, Scope *S) {
ASTContext &Context = Sema.Context;
LookupResult Result(Sema, &Context.Idents.get("objc_super"), SourceLocation(),
Sema.LookupName(Result, S);
if (Result.getResultKind() == LookupResult::Found)
if (const TagDecl *TD = Result.getAsSingle<TagDecl>())
void Sema::LookupNecessaryTypesForBuiltin(Scope *S, unsigned ID) {
if (ID == Builtin::BIobjc_msgSendSuper)
LookupPredefedObjCSuperType(*this, S);
/// Determine whether we can declare a special member function within
/// the class at this point.
static bool CanDeclareSpecialMemberFunction(const CXXRecordDecl *Class) {
// We need to have a definition for the class.
if (!Class->getDefinition() || Class->isDependentContext())
return false;
// We can't be in the middle of defining the class.
return !Class->isBeingDefined();
void Sema::ForceDeclarationOfImplicitMembers(CXXRecordDecl *Class) {
if (!CanDeclareSpecialMemberFunction(Class))
// If the default constructor has not yet been declared, do so now.
if (Class->needsImplicitDefaultConstructor())
// If the copy constructor has not yet been declared, do so now.
if (Class->needsImplicitCopyConstructor())
// If the copy assignment operator has not yet been declared, do so now.
if (Class->needsImplicitCopyAssignment())
if (getLangOpts().CPlusPlus11) {
// If the move constructor has not yet been declared, do so now.
if (Class->needsImplicitMoveConstructor())
// If the move assignment operator has not yet been declared, do so now.
if (Class->needsImplicitMoveAssignment())
// If the destructor has not yet been declared, do so now.
if (Class->needsImplicitDestructor())
/// Determine whether this is the name of an implicitly-declared
/// special member function.
static bool isImplicitlyDeclaredMemberFunctionName(DeclarationName Name) {
switch (Name.getNameKind()) {
case DeclarationName::CXXConstructorName:
case DeclarationName::CXXDestructorName:
return true;
case DeclarationName::CXXOperatorName:
return Name.getCXXOverloadedOperator() == OO_Equal;
return false;
/// If there are any implicit member functions with the given name
/// that need to be declared in the given declaration context, do so.
static void DeclareImplicitMemberFunctionsWithName(Sema &S,
DeclarationName Name,
SourceLocation Loc,
const DeclContext *DC) {
if (!DC)
switch (Name.getNameKind()) {
case DeclarationName::CXXConstructorName:
if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(DC))
if (Record->getDefinition() && CanDeclareSpecialMemberFunction(Record)) {
CXXRecordDecl *Class = const_cast<CXXRecordDecl *>(Record);
if (Record->needsImplicitDefaultConstructor())
if (Record->needsImplicitCopyConstructor())
if (S.getLangOpts().CPlusPlus11 &&
case DeclarationName::CXXDestructorName:
if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(DC))
if (Record->getDefinition() && Record->needsImplicitDestructor() &&
S.DeclareImplicitDestructor(const_cast<CXXRecordDecl *>(Record));
case DeclarationName::CXXOperatorName:
if (Name.getCXXOverloadedOperator() != OO_Equal)
if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(DC)) {
if (Record->getDefinition() && CanDeclareSpecialMemberFunction(Record)) {
CXXRecordDecl *Class = const_cast<CXXRecordDecl *>(Record);
if (Record->needsImplicitCopyAssignment())
if (S.getLangOpts().CPlusPlus11 &&
case DeclarationName::CXXDeductionGuideName:
S.DeclareImplicitDeductionGuides(Name.getCXXDeductionGuideTemplate(), Loc);
// Adds all qualifying matches for a name within a decl context to the
// given lookup result. Returns true if any matches were found.
static bool LookupDirect(Sema &S, LookupResult &R, const DeclContext *DC) {
bool Found = false;
// Lazily declare C++ special member functions.
if (S.getLangOpts().CPlusPlus)
DeclareImplicitMemberFunctionsWithName(S, R.getLookupName(), R.getNameLoc(),
// Perform lookup into this declaration context.
DeclContext::lookup_result DR = DC->lookup(R.getLookupName());
for (NamedDecl *D : DR) {
if ((D = R.getAcceptableDecl(D))) {
Found = true;
if (!Found && DC->isTranslationUnit() && S.LookupBuiltin(R))
return true;
if (R.getLookupName().getNameKind()
!= DeclarationName::CXXConversionFunctionName ||
R.getLookupName().getCXXNameType()->isDependentType() ||
return Found;
// C++ [temp.mem]p6:
// A specialization of a conversion function template is not found by
// name lookup. Instead, any conversion function templates visible in the
// context of the use are considered. [...]
const CXXRecordDecl *Record = cast<CXXRecordDecl>(DC);
if (!Record->isCompleteDefinition())
return Found;
// For conversion operators, 'operator auto' should only match
// 'operator auto'. Since 'auto' is not a type, it shouldn't be considered
// as a candidate for template substitution.
auto *ContainedDeducedType =
if (R.getLookupName().getNameKind() ==
DeclarationName::CXXConversionFunctionName &&
ContainedDeducedType && ContainedDeducedType->isUndeducedType())
return Found;
for (CXXRecordDecl::conversion_iterator U = Record->conversion_begin(),
UEnd = Record->conversion_end(); U != UEnd; ++U) {
FunctionTemplateDecl *ConvTemplate = dyn_cast<FunctionTemplateDecl>(*U);
if (!ConvTemplate)
// When we're performing lookup for the purposes of redeclaration, just
// add the conversion function template. When we deduce template
// arguments for specializations, we'll end up unifying the return
// type of the new declaration with the type of the function template.
if (R.isForRedeclaration()) {
Found = true;
// C++ [temp.mem]p6:
// [...] For each such operator, if argument deduction succeeds
// (, the resulting specialization is used as if found by
// name lookup.
// When referencing a conversion function for any purpose other than
// a redeclaration (such that we'll be building an expression with the
// result), perform template argument deduction and place the
// specialization into the result set. We do this to avoid forcing all
// callers to perform special deduction for conversion functions.
TemplateDeductionInfo Info(R.getNameLoc());
FunctionDecl *Specialization = nullptr;
const FunctionProtoType *ConvProto
= ConvTemplate->getTemplatedDecl()->getType()->getAs<FunctionProtoType>();
assert(ConvProto && "Nonsensical conversion function template type");
// Compute the type of the function that we would expect the conversion
// function to have, if it were to match the name given.
// FIXME: Calling convention!
FunctionProtoType::ExtProtoInfo EPI = ConvProto->getExtProtoInfo();
EPI.ExtInfo = EPI.ExtInfo.withCallingConv(CC_C);
EPI.ExceptionSpec = EST_None;
QualType ExpectedType
= R.getSema().Context.getFunctionType(R.getLookupName().getCXXNameType(),
None, EPI);
// Perform template argument deduction against the type that we would
// expect the function to have.
if (R.getSema().DeduceTemplateArguments(ConvTemplate, nullptr, ExpectedType,
Specialization, Info)
== Sema::TDK_Success) {
Found = true;
return Found;
// Performs C++ unqualified lookup into the given file context.
static bool
CppNamespaceLookup(Sema &S, LookupResult &R, ASTContext &Context,
DeclContext *NS, UnqualUsingDirectiveSet &UDirs) {
assert(NS && NS->isFileContext() && "CppNamespaceLookup() requires namespace!");
// Perform direct name lookup into the LookupCtx.
bool Found = LookupDirect(S, R, NS);
// Perform direct name lookup into the namespaces nominated by the
// using directives whose common ancestor is this namespace.
for (const UnqualUsingEntry &UUE : UDirs.getNamespacesFor(NS))
if (LookupDirect(S, R, UUE.getNominatedNamespace()))
Found = true;
return Found;
static bool isNamespaceOrTranslationUnitScope(Scope *S) {
if (DeclContext *Ctx = S->getEntity())
return Ctx->isFileContext();
return false;
/// Find the outer declaration context from this scope. This indicates the
/// context that we should search up to (exclusive) before considering the
/// parent of the specified scope.
static DeclContext *findOuterContext(Scope *S) {
for (Scope *OuterS = S->getParent(); OuterS; OuterS = OuterS->getParent())
if (DeclContext *DC = OuterS->getLookupEntity())
return DC;
return nullptr;
namespace {
/// An RAII object to specify that we want to find block scope extern
/// declarations.
struct FindLocalExternScope {
FindLocalExternScope(LookupResult &R)
: R(R), OldFindLocalExtern(R.getIdentifierNamespace() &
Decl::IDNS_LocalExtern) {
R.setFindLocalExtern(R.getIdentifierNamespace() &
(Decl::IDNS_Ordinary | Decl::IDNS_NonMemberOperator));
void restore() {
~FindLocalExternScope() {
LookupResult &R;
bool OldFindLocalExtern;
} // end anonymous namespace
bool Sema::CppLookupName(LookupResult &R, Scope *S) {
assert(getLangOpts().CPlusPlus && "Can perform only C++ lookup");
DeclarationName Name = R.getLookupName();
Sema::LookupNameKind NameKind = R.getLookupKind();
// If this is the name of an implicitly-declared special member function,
// go through the scope stack to implicitly declare
if (isImplicitlyDeclaredMemberFunctionName(Name)) {
for (Scope *PreS = S; PreS; PreS = PreS->getParent())
if (DeclContext *DC = PreS->getEntity())
DeclareImplicitMemberFunctionsWithName(*this, Name, R.getNameLoc(), DC);
// Implicitly declare member functions with the name we're looking for, if in
// fact we are in a scope where it matters.
Scope *Initial = S;
I = IdResolver.begin(Name),
IEnd = IdResolver.end();
// First we lookup local scope.
// We don't consider using-directives, as per 7.3.4.p1 [namespace.udir]
// ...During unqualified name lookup (3.4.1), the names appear as if
// they were declared in the nearest enclosing namespace which contains
// both the using-directive and the nominated namespace.
// [Note: in this context, "contains" means "contains directly or
// indirectly".
// For example:
// namespace A { int i; }
// void foo() {
// int i;
// {
// using namespace A;
// ++i; // finds local 'i', A::i appears at global scope
// }
// }
UnqualUsingDirectiveSet UDirs(*this);
bool VisitedUsingDirectives = false;
bool LeftStartingScope = false;
// When performing a scope lookup, we want to find local extern decls.
FindLocalExternScope FindLocals(R);
for (; S && !isNamespaceOrTranslationUnitScope(S); S = S->getParent()) {
bool SearchNamespaceScope = true;
// Check whether the IdResolver has anything in this scope.
for (; I != IEnd && S->isDeclScope(*I); ++I) {
if (NamedDecl *ND = R.getAcceptableDecl(*I)) {
if (NameKind == LookupRedeclarationWithLinkage &&
!(*I)->isTemplateParameter()) {
// If it's a template parameter, we still find it, so we can diagnose
// the invalid redeclaration.
// Determine whether this (or a previous) declaration is
// out-of-scope.
if (!LeftStartingScope && !Initial->isDeclScope(*I))
LeftStartingScope = true;
// If we found something outside of our starting scope that
// does not have linkage, skip it.
if (LeftStartingScope && !((*I)->hasLinkage())) {
} else {
// We found something in this scope, we should not look at the
// namespace scope
SearchNamespaceScope = false;
if (!SearchNamespaceScope) {
if (S->isClassScope())
if (CXXRecordDecl *Record =
return true;
if (NameKind == LookupLocalFriendName && !S->isClassScope()) {
// C++11 [class.friend]p11:
// If a friend declaration appears in a local class and the name
// specified is an unqualified name, a prior declaration is
// looked up without considering scopes that are outside the
// innermost enclosing non-class scope.
return false;
if (DeclContext *Ctx = S->getLookupEntity()) {
DeclContext *OuterCtx = findOuterContext(S);
for (; Ctx && !Ctx->Equals(OuterCtx); Ctx = Ctx->getLookupParent()) {
// We do not directly look into transparent contexts, since
// those entities will be found in the nearest enclosing
// non-transparent context.
if (Ctx->isTransparentContext())
// We do not look directly into function or method contexts,
// since all of the local variables and parameters of the
// function/method are present within the Scope.
if (Ctx->isFunctionOrMethod()) {
// If we have an Objective-C instance method, look for ivars
// in the corresponding interface.
if (ObjCMethodDecl *Method = dyn_cast<ObjCMethodDecl>(Ctx)) {
if (Method->isInstanceMethod() && Name.getAsIdentifierInfo())
if (ObjCInterfaceDecl *Class = Method->getClassInterface()) {
ObjCInterfaceDecl *ClassDeclared;
if (ObjCIvarDecl *Ivar = Class->lookupInstanceVariable(
ClassDeclared)) {
if (NamedDecl *ND = R.getAcceptableDecl(Ivar)) {
return true;
// If this is a file context, we need to perform unqualified name
// lookup considering using directives.
if (Ctx->isFileContext()) {
// If we haven't handled using directives yet, do so now.
if (!VisitedUsingDirectives) {
// Add using directives from this context up to the top level.
for (DeclContext *UCtx = Ctx; UCtx; UCtx = UCtx->getParent()) {
if (UCtx->isTransparentContext())
UDirs.visit(UCtx, UCtx);
// Find the innermost file scope, so we can add using directives
// from local scopes.
Scope *InnermostFileScope = S;
while (InnermostFileScope &&
InnermostFileScope = InnermostFileScope->getParent();
UDirs.visitScopeChain(Initial, InnermostFileScope);
VisitedUsingDirectives = true;
if (CppNamespaceLookup(*this, R, Context, Ctx, UDirs)) {
return true;
// Perform qualified name lookup into this context.
// FIXME: In some cases, we know that every name that could be found by
// this qualified name lookup will also be on the identifier chain. For
// example, inside a class without any base classes, we never need to
// perform qualified lookup because all of the members are on top of the
// identifier chain.
if (LookupQualifiedName(R, Ctx, /*InUnqualifiedLookup=*/true))
return true;
// Stop if we ran out of scopes.
// FIXME: This really, really shouldn't be happening.
if (!S) return false;
// If we are looking for members, no need to look into global/namespace scope.
if (NameKind == LookupMemberName)
return false;
// Collect UsingDirectiveDecls in all scopes, and recursively all
// nominated namespaces by those using-directives.
// FIXME: Cache this sorted list in Scope structure, and DeclContext, so we
// don't build it for each lookup!
if (!VisitedUsingDirectives) {
UDirs.visitScopeChain(Initial, S);
// If we're not performing redeclaration lookup, do not look for local
// extern declarations outside of a function scope.
if (!R.isForRedeclaration())
// Lookup namespace scope, and global scope.
// Unqualified name lookup in C++ requires looking into scopes
// that aren't strictly lexical, and therefore we walk through the
// context as well as walking through the scopes.
for (; S; S = S->getParent()) {
// Check whether the IdResolver has anything in this scope.
bool Found = false;
for (; I != IEnd && S->isDeclScope(*I); ++I) {
if (NamedDecl *ND = R.getAcceptableDecl(*I)) {
// We found something. Look for anything else in our scope
// with this same name and in an acceptable identifier
// namespace, so that we can construct an overload set if we
// need to.
Found = true;
if (Found && S->isTemplateParamScope()) {
return true;
DeclContext *Ctx = S->getLookupEntity();
if (Ctx) {
DeclContext *OuterCtx = findOuterContext(S);
for (; Ctx && !Ctx->Equals(OuterCtx); Ctx = Ctx->getLookupParent()) {
// We do not directly look into transparent contexts, since
// those entities will be found in the nearest enclosing
// non-transparent context.
if (Ctx->isTransparentContext())
// If we have a context, and it's not a context stashed in the
// template parameter scope for an out-of-line definition, also
// look into that context.
if (!(Found && S->isTemplateParamScope())) {
assert(Ctx->isFileContext() &&
"We should have been looking only at file context here already.");
// Look into context considering using-directives.
if (CppNamespaceLookup(*this, R, Context, Ctx, UDirs))
Found = true;
if (Found) {
return true;
if (R.isForRedeclaration() && !Ctx->isTransparentContext())
return false;
if (R.isForRedeclaration() && Ctx && !Ctx->isTransparentContext())
return false;
return !R.empty();
void Sema::makeMergedDefinitionVisible(NamedDecl *ND) {
if (auto *M = getCurrentModule())
Context.mergeDefinitionIntoModule(ND, M);
// We're not building a module; just make the definition visible.
// If ND is a template declaration, make the template parameters
// visible too. They're not (necessarily) within a mergeable DeclContext.
if (auto *TD = dyn_cast<TemplateDecl>(ND))
for (auto *Param : *TD->getTemplateParameters())
/// Find the module in which the given declaration was defined.
static Module *getDefiningModule(Sema &S, Decl *Entity) {
if (FunctionDecl *FD = dyn_cast<FunctionDecl>(Entity)) {
// If this function was instantiated from a template, the defining module is
// the module containing the pattern.
if (FunctionDecl *Pattern = FD->getTemplateInstantiationPattern())
Entity = Pattern;
} else if (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Entity)) {
if (CXXRecordDecl *Pattern = RD->getTemplateInstantiationPattern())
Entity = Pattern;
} else if (EnumDecl *ED = dyn_cast<EnumDecl>(Entity)) {
if (auto *Pattern = ED->getTemplateInstantiationPattern())
Entity = Pattern;
} else if (VarDecl *VD = dyn_cast<VarDecl>(Entity)) {
if (VarDecl *Pattern = VD->getTemplateInstantiationPattern())
Entity = Pattern;
// Walk up to the containing context. That might also have been instantiated
// from a template.
DeclContext *Context = Entity->getLexicalDeclContext();
if (Context->isFileContext())
return S.getOwningModule(Entity);
return getDefiningModule(S, cast<Decl>(Context));
llvm::DenseSet<Module*> &Sema::getLookupModules() {
unsigned N = CodeSynthesisContexts.size();
for (unsigned I = CodeSynthesisContextLookupModules.size();
I != N; ++I) {
Module *M = CodeSynthesisContexts[I].Entity ?
getDefiningModule(*this, CodeSynthesisContexts[I].Entity) :
if (M && !LookupModulesCache.insert(M).second)
M = nullptr;
return LookupModulesCache;
/// Determine whether the module M is part of the current module from the
/// perspective of a module-private visibility check.
static bool isInCurrentModule(const Module *M, const LangOptions &LangOpts) {
// If M is the global module fragment of a module that we've not yet finished
// parsing, then it must be part of the current module.
return M->getTopLevelModuleName() == LangOpts.CurrentModule ||
(M->Kind == Module::GlobalModuleFragment && !M->Parent);
bool Sema::hasVisibleMergedDefinition(NamedDecl *Def) {
for (const Module *Merged : Context.getModulesWithMergedDefinition(Def))
if (isModuleVisible(Merged))
return true;
return false;
bool Sema::hasMergedDefinitionInCurrentModule(NamedDecl *Def) {
for (const Module *Merged : Context.getModulesWithMergedDefinition(Def))
if (isInCurrentModule(Merged, getLangOpts()))
return true;
return false;
template<typename ParmDecl>
static bool
hasVisibleDefaultArgument(Sema &S, const ParmDecl *D,
llvm::SmallVectorImpl<Module *> *Modules) {
if (!D->hasDefaultArgument())
return false;
while (D) {
auto &DefaultArg = D->getDefaultArgStorage();
if (!DefaultArg.isInherited() && S.isVisible(D))
return true;
if (!DefaultArg.isInherited() && Modules) {
auto *NonConstD = const_cast<ParmDecl*>(D);
// If there was a previous default argument, maybe its parameter is visible.
D = DefaultArg.getInheritedFrom();
return false;
bool Sema::hasVisibleDefaultArgument(const NamedDecl *D,
llvm::SmallVectorImpl<Module *> *Modules) {
if (auto *P = dyn_cast<TemplateTypeParmDecl>(D))
return ::hasVisibleDefaultArgument(*this, P, Modules);
if (auto *P = dyn_cast<NonTypeTemplateParmDecl>(D))
return ::hasVisibleDefaultArgument(*this, P, Modules);
return ::hasVisibleDefaultArgument(*this, cast<TemplateTemplateParmDecl>(D),
template<typename Filter>
static bool hasVisibleDeclarationImpl(Sema &S, const NamedDecl *D,
llvm::SmallVectorImpl<Module *> *Modules,
Filter F) {
bool HasFilteredRedecls = false;
for (auto *Redecl : D->redecls()) {
auto *R = cast<NamedDecl>(Redecl);
if (!F(R))
if (S.isVisible(R))
return true;
HasFilteredRedecls = true;
if (Modules)
// Only return false if there is at least one redecl that is not filtered out.
if (HasFilteredRedecls)
return false;
return true;
bool Sema::hasVisibleExplicitSpecialization(
const NamedDecl *D, llvm::SmallVectorImpl<Module *> *Modules) {
return hasVisibleDeclarationImpl(*this, D, Modules, [](const NamedDecl *D) {
if (auto *RD = dyn_cast<CXXRecordDecl>(D))
return RD->getTemplateSpecializationKind() == TSK_ExplicitSpecialization;
if (auto *FD = dyn_cast<FunctionDecl>(D))
return FD->getTemplateSpecializationKind() == TSK_ExplicitSpecialization;
if (auto *VD = dyn_cast<VarDecl>(D))
return VD->getTemplateSpecializationKind() == TSK_ExplicitSpecialization;
llvm_unreachable("unknown explicit specialization kind");
bool Sema::hasVisibleMemberSpecialization(
const NamedDecl *D, llvm::SmallVectorImpl<Module *> *Modules) {
assert(isa<CXXRecordDecl>(D->getDeclContext()) &&
"not a member specialization");
return hasVisibleDeclarationImpl(*this, D, Modules, [](const NamedDecl *D) {
// If the specialization is declared at namespace scope, then it's a member
// specialization declaration. If it's lexically inside the class
// definition then it was instantiated.
// FIXME: This is a hack. There should be a better way to determine this.
// FIXME: What about MS-style explicit specializations declared within a
// class definition?
return D->getLexicalDeclContext()->isFileContext();
/// Determine whether a declaration is visible to name lookup.
/// This routine determines whether the declaration D is visible in the current
/// lookup context, taking into account the current template instantiation
/// stack. During template instantiation, a declaration is visible if it is
/// visible from a module containing any entity on the template instantiation
/// path (by instantiating a template, you allow it to see the declarations that
/// your module can see, including those later on in your module).
bool LookupResult::isVisibleSlow(Sema &SemaRef, NamedDecl *D) {
assert(!D->isUnconditionallyVisible() &&
"should not call this: not in slow case");
Module *DeclModule = SemaRef.getOwningModule(D);
assert(DeclModule && "hidden decl has no owning module");
// If the owning module is visible, the decl is visible.
if (SemaRef.isModuleVisible(DeclModule, D->isModulePrivate()))
return true;
// Determine whether a decl context is a file context for the purpose of
// visibility. This looks through some (export and linkage spec) transparent
// contexts, but not others (enums).
auto IsEffectivelyFileContext = [](const DeclContext *DC) {
return DC->isFileContext() || isa<LinkageSpecDecl>(DC) ||
// If this declaration is not at namespace scope
// then it is visible if its lexical parent has a visible definition.
DeclContext *DC = D->getLexicalDeclContext();
if (DC && !IsEffectivelyFileContext(DC)) {
// For a parameter, check whether our current template declaration's
// lexical context is visible, not whether there's some other visible
// definition of it, because parameters aren't "within" the definition.
// In C++ we need to check for a visible definition due to ODR merging,
// and in C we must not because each declaration of a function gets its own
// set of declarations for tags in prototype scope.
bool VisibleWithinParent;
if (D->isTemplateParameter()) {
bool SearchDefinitions = true;
if (const auto *DCD = dyn_cast<Decl>(DC)) {
if (const auto *TD = DCD->getDescribedTemplate()) {
TemplateParameterList *TPL = TD->getTemplateParameters();
auto Index = getDepthAndIndex(D).second;
SearchDefinitions = Index >= TPL->size() || TPL->getParam(Index) != D;
if (SearchDefinitions)
VisibleWithinParent = SemaRef.hasVisibleDefinition(cast<NamedDecl>(DC));
VisibleWithinParent = isVisible(SemaRef, cast<NamedDecl>(DC));
} else if (isa<ParmVarDecl>(D) ||
(isa<FunctionDecl>(DC) && !SemaRef.getLangOpts().CPlusPlus))
VisibleWithinParent = isVisible(SemaRef, cast<NamedDecl>(DC));
else if (D->isModulePrivate()) {
// A module-private declaration is only visible if an enclosing lexical
// parent was merged with another definition in the current module.
VisibleWithinParent = false;
do {
if (SemaRef.hasMergedDefinitionInCurrentModule(cast<NamedDecl>(DC))) {
VisibleWithinParent = true;
DC = DC->getLexicalParent();
} while (!IsEffectivelyFileContext(DC));
} else {
VisibleWithinParent = SemaRef.hasVisibleDefinition(cast<NamedDecl>(DC));
if (VisibleWithinParent && SemaRef.CodeSynthesisContexts.empty() &&
// FIXME: Do something better in this case.
!SemaRef.getLangOpts().ModulesLocalVisibility) {
// Cache the fact that this declaration is implicitly visible because
// its parent has a visible definition.
return VisibleWithinParent;
return false;
bool Sema::isModuleVisible(const Module *M, bool ModulePrivate) {
// The module might be ordinarily visible. For a module-private query, that
// means it is part of the current module. For any other query, that means it
// is in our visible module set.
if (ModulePrivate) {
if (isInCurrentModule(M, getLangOpts()))
return true;
} else {
if (VisibleModules.isVisible(M))
return true;
// Otherwise, it might be visible by virtue of the query being within a
// template instantiation or similar that is permitted to look inside M.
// Find the extra places where we need to look.
const auto &LookupModules = getLookupModules();
if (LookupModules.empty())
return false;
// If our lookup set contains the module, it's visible.
if (LookupModules.count(M))
return true;
// For a module-private query, that's everywhere we get to look.
if (ModulePrivate)
return false;
// Check whether M is transitively exported to an import of the lookup set.
return llvm::any_of(LookupModules, [&](const Module *LookupM) {
return LookupM->isModuleVisible(M);
bool Sema::isVisibleSlow(const NamedDecl *D) {
return LookupResult::isVisible(*this, const_cast<NamedDecl*>(D));
bool Sema::shouldLinkPossiblyHiddenDecl(LookupResult &R, const NamedDecl *New) {
// FIXME: If there are both visible and hidden declarations, we need to take
// into account whether redeclaration is possible. Example:
// Non-imported module:
// int f(T); // #1
// Some TU:
// static int f(U); // #2, not a redeclaration of #1
// int f(T); // #3, finds both, should link with #1 if T != U, but
// // with #2 if T == U; neither should be ambiguous.
for (auto *D : R) {
if (isVisible(D))
return true;
assert(D->isExternallyDeclarable() &&
"should not have hidden, non-externally-declarable result here");
// This function is called once "New" is essentially complete, but before a
// previous declaration is attached. We can't query the linkage of "New" in
// general, because attaching the previous declaration can change the
// linkage of New to match the previous declaration.
// However, because we've just determined that there is no *visible* prior
// declaration, we can compute the linkage here. There are two possibilities:
// * This is not a redeclaration; it's safe to compute the linkage now.
// * This is a redeclaration of a prior declaration that is externally
// redeclarable. In that case, the linkage of the declaration is not
// changed by attaching the prior declaration, because both are externally
// declarable (and thus ExternalLinkage or VisibleNoLinkage).
// FIXME: This is subtle and fragile.
return New->isExternallyDeclarable();
/// Retrieve the visible declaration corresponding to D, if any.
/// This routine determines whether the declaration D is visible in the current
/// module, with the current imports. If not, it checks whether any
/// redeclaration of D is visible, and if so, returns that declaration.
/// \returns D, or a visible previous declaration of D, whichever is more recent
/// and visible. If no declaration of D is visible, returns null.
static NamedDecl *findAcceptableDecl(Sema &SemaRef, NamedDecl *D,
unsigned IDNS) {
assert(!LookupResult::isVisible(SemaRef, D) && "not in slow case");
for (auto RD : D->redecls()) {
// Don't bother with extra checks if we already know this one isn't visible.
if (RD == D)
auto ND = cast<NamedDecl>(RD);
// FIXME: This is wrong in the case where the previous declaration is not
// visible in the same scope as D. This needs to be done much more
// carefully.
if (ND->isInIdentifierNamespace(IDNS) &&
LookupResult::isVisible(SemaRef, ND))
return ND;
return nullptr;
bool Sema::hasVisibleDeclarationSlow(const NamedDecl *D,
llvm::SmallVectorImpl<Module *> *Modules) {
assert(!isVisible(D) && "not in slow case");
return hasVisibleDeclarationImpl(*this, D, Modules,
[](const NamedDecl *) { return true; });
NamedDecl *LookupResult::getAcceptableDeclSlow(NamedDecl *D) const {
if (auto *ND = dyn_cast<NamespaceDecl>(D)) {
// Namespaces are a bit of a special case: we expect there to be a lot of
// redeclarations of some namespaces, all declarations of a namespace are
// essentially interchangeable, all declarations are found by name lookup
// if any is, and namespaces are never looked up during template
// instantiation. So we benefit from caching the check in this case, and
// it is correct to do so.
auto *Key = ND->getCanonicalDecl();
if (auto *Acceptable = getSema().VisibleNamespaceCache.lookup(Key))
return Acceptable;
auto *Acceptable = isVisible(getSema(), Key)
? Key
: findAcceptableDecl(getSema(), Key, IDNS);
if (Acceptable)
getSema().VisibleNamespaceCache.insert(std::make_pair(Key, Acceptable));
return Acceptable;
return findAcceptableDecl(getSema(), D, IDNS);
/// Perform unqualified name lookup starting from a given
/// scope.
/// Unqualified name lookup (C++ [basic.lookup.unqual], C99 6.2.1) is
/// used to find names within the current scope. For example, 'x' in
/// @code
/// int x;
/// int f() {
/// return x; // unqualified name look finds 'x' in the global scope
/// }
/// @endcode
/// Different lookup criteria can find different names. For example, a
/// particular scope can have both a struct and a function of the same
/// name, and each can be found by certain lookup criteria. For more
/// information about lookup criteria, see the documentation for the
/// class LookupCriteria.
/// @param S The scope from which unqualified name lookup will
/// begin. If the lookup criteria permits, name lookup may also search
/// in the parent scopes.
/// @param [in,out] R Specifies the lookup to perform (e.g., the name to
/// look up and the lookup kind), and is updated with the results of lookup
/// including zero or more declarations and possibly additional information
/// used to diagnose ambiguities.
/// @returns \c true if lookup succeeded and false otherwise.
bool Sema::LookupName(LookupResult &R, Scope *S, bool AllowBuiltinCreation) {
DeclarationName Name = R.getLookupName();
if (!Name) return false;
LookupNameKind NameKind = R.getLookupKind();
if (!getLangOpts().CPlusPlus) {
// Unqualified name lookup in C/Objective-C is purely lexical, so
// search in the declarations attached to the name.
if (NameKind == Sema::LookupRedeclarationWithLinkage) {
// Find the nearest non-transparent declaration scope.
while (!(S->getFlags() & Scope::DeclScope) ||
(S->getEntity() && S->getEntity()->isTransparentContext()))
S = S->getParent();
// When performing a scope lookup, we want to find local extern decls.
FindLocalExternScope FindLocals(R);
// Scan up the scope chain looking for a decl that matches this
// identifier that is in the appropriate namespace. This search
// should not take long, as shadowing of names is uncommon, and
// deep shadowing is extremely uncommon.
bool LeftStartingScope = false;
for (IdentifierResolver::iterator I = IdResolver.begin(Name),
IEnd = IdResolver.end();
I != IEnd; ++I)
if (NamedDecl *D = R.getAcceptableDecl(*I)) {
if (NameKind == LookupRedeclarationWithLinkage) {
// Determine whether this (or a previous) declaration is
// out-of-scope.
if (!LeftStartingScope && !S->isDeclScope(*I))
LeftStartingScope = true;
// If we found something outside of our starting scope that
// does not have linkage, skip it.
if (LeftStartingScope && !((*I)->hasLinkage())) {
else if (NameKind == LookupObjCImplicitSelfParam &&
// Check whether there are any other declarations with the same name
// and in the same scope.
if (I != IEnd) {
// Find the scope in which this declaration was declared (if it
// actually exists in a Scope).
while (S && !S->isDeclScope(D))
S = S->getParent();
// If the scope containing the declaration is the translation unit,
// then we'll need to perform our checks based on the matching
// DeclContexts rather than matching scopes.
if (S && isNamespaceOrTranslationUnitScope(S))
S = nullptr;
// Compute the DeclContext, if we need it.
DeclContext *DC = nullptr;
if (!S)
DC = (*I)->getDeclContext()->getRedeclContext();
IdentifierResolver::iterator LastI = I;
for (++LastI; LastI != IEnd; ++LastI) {
if (S) {
// Match based on scope.
if (!S->isDeclScope(*LastI))
} else {
// Match based on DeclContext.
DeclContext *LastDC
= (*LastI)->getDeclContext()->getRedeclContext();
if (!LastDC->Equals(DC))
// If the declaration is in the right namespace and visible, add it.
if (NamedDecl *LastD = R.getAcceptableDecl(*LastI))
return true;
} else {
// Perform C++ unqualified name lookup.
if (CppLookupName(R, S))
return true;
// If we didn't find a use of this identifier, and if the identifier
// corresponds to a compiler builtin, create the decl object for the builtin
// now, injecting it into translation unit scope, and return it.
if (AllowBuiltinCreation && LookupBuiltin(R))
return true;
// If we didn't find a use of this identifier, the ExternalSource
// may be able to handle the situation.
// Note: some lookup failures are expected!
// See e.g. R.isForRedeclaration().
return (ExternalSource && ExternalSource->LookupUnqualified(R, S));
/// Perform qualified name lookup in the namespaces nominated by
/// using directives by the given context.
/// C++98 [namespace.qual]p2:
/// Given X::m (where X is a user-declared namespace), or given \::m
/// (where X is the global namespace), let S be the set of all
/// declarations of m in X and in the transitive closure of all
/// namespaces nominated by using-directives in X and its used
/// namespaces, except that using-directives are ignored in any
/// namespace, including X, directly containing one or more
/// declarations of m. No namespace is searched more than once in
/// the lookup of a name. If S is the empty set, the program is
/// ill-formed. Otherwise, if S has exactly one member, or if the
/// context of the reference is a using-declaration
/// (namespace.udecl), S is the required set of declarations of
/// m. Otherwise if the use of m is not one that allows a unique
/// declaration to be chosen from S, the program is ill-formed.
/// C++98 [namespace.qual]p5:
/// During the lookup of a qualified namespace member name, if the
/// lookup finds more than one declaration of the member, and if one
/// declaration introduces a class name or enumeration name and the
/// other declarations either introduce the same object, the same
/// enumerator or a set of functions, the non-type name hides the
/// class or enumeration name if and only if the declarations are
/// from the same namespace; otherwise (the declarations are from
/// different namespaces), the program is ill-formed.
static bool LookupQualifiedNameInUsingDirectives(Sema &S, LookupResult &R,
DeclContext *StartDC) {
assert(StartDC->isFileContext() && "start context is not a file context");
// We have not yet looked into these namespaces, much less added
// their "using-children" to the queue.
SmallVector<NamespaceDecl*, 8> Queue;
// We have at least added all these contexts to the queue.
llvm::SmallPtrSet<DeclContext*, 8> Visited;
// We have already looked into the initial namespace; seed the queue
// with its using-children.
for (auto *I : StartDC->using_directives()) {
NamespaceDecl *ND = I->getNominatedNamespace()->getOriginalNamespace();
if (S.isVisible(I) && Visited.insert(ND).second)
// The easiest way to implement the restriction in [namespace.qual]p5
// is to check whether any of the individual results found a tag
// and, if so, to declare an ambiguity if the final result is not
// a tag.
bool FoundTag = false;
bool FoundNonTag = false;
LookupResult LocalR(LookupResult::Temporary, R);
bool Found = false;
while (!Queue.empty()) {
NamespaceDecl *ND = Queue.pop_back_val();
// We go through some convolutions here to avoid copying results
// between LookupResults.
bool UseLocal = !R.empty();
LookupResult &DirectR = UseLocal ? LocalR : R;
bool FoundDirect = LookupDirect(S, DirectR, ND);
if (FoundDirect) {
// First do any local hiding.
// If the local result is a tag, remember that.
if (DirectR.isSingleTagDecl())
FoundTag = true;
FoundNonTag = true;
// Append the local results to the total results if necessary.
if (UseLocal) {
// If we find names in this namespace, ignore its using directives.
if (FoundDirect) {
Found = true;
for (auto I : ND->using_directives()) {
NamespaceDecl *Nom = I->getNominatedNamespace();
if (S.isVisible(I) && Visited.insert(Nom).second)
if (Found) {
if (FoundTag && FoundNonTag)
return Found;
/// Perform qualified name lookup into a given context.
/// Qualified name lookup (C++ [basic.lookup.qual]) is used to find
/// names when the context of those names is explicit specified, e.g.,
/// "std::vector" or "x->member", or as part of unqualified name lookup.
/// Different lookup criteria can find different names. For example, a
/// particular scope can have both a struct and a function of the same
/// name, and each can be found by certain lookup criteria. For more
/// information about lookup criteria, see the documentation for the
/// class LookupCriteria.
/// \param R captures both the lookup criteria and any lookup results found.
/// \param LookupCtx The context in which qualified name lookup will
/// search. If the lookup criteria permits, name lookup may also search
/// in the parent contexts or (for C++ classes) base classes.
/// \param InUnqualifiedLookup true if this is qualified name lookup that
/// occurs as part of unqualified name lookup.
/// \returns true if lookup succeeded, false if it failed.
bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
bool InUnqualifiedLookup) {
assert(LookupCtx && "Sema::LookupQualifiedName requires a lookup context");
if (!R.getLookupName())
return false;
// Make sure that the declaration context is complete.
assert((!isa<TagDecl>(LookupCtx) ||
LookupCtx->isDependentContext() ||
cast<TagDecl>(LookupCtx)->isCompleteDefinition() ||
cast<TagDecl>(LookupCtx)->isBeingDefined()) &&
"Declaration context must already be complete!");
struct QualifiedLookupInScope {
bool oldVal;
DeclContext *Context;
// Set flag in DeclContext informing debugger that we're looking for qualified name
QualifiedLookupInScope(DeclContext *ctx) : Context(ctx) {
oldVal = ctx->setUseQualifiedLookup();
~QualifiedLookupInScope() {
} QL(LookupCtx);
if (LookupDirect(*this, R, LookupCtx)) {
if (isa<CXXRecordDecl>(LookupCtx))
return true;
// Don't descend into implied contexts for redeclarations.
// C++98 [namespace.qual]p6:
// In a declaration for a namespace member in which the
// declarator-id is a qualified-id, given that the qualified-id
// for the namespace member has the form
// nested-name-specifier unqualified-id
// the unqualified-id shall name a member of the namespace
// designated by the nested-name-specifier.
// See also [class.mfct]p5 and []p2.
if (R.isForRedeclaration())
return false;
// If this is a namespace, look it up in the implied namespaces.
if (LookupCtx->isFileContext())
return LookupQualifiedNameInUsingDirectives(*this, R, LookupCtx);
// If this isn't a C++ class, we aren't allowed to look into base
// classes, we're done.
CXXRecordDecl *LookupRec = dyn_cast<CXXRecordDecl>(LookupCtx);
if (!LookupRec || !LookupRec->getDefinition())
return false;
// We're done for lookups that can never succeed for C++ classes.
if (R.getLookupKind() == LookupOperatorName ||
R.getLookupKind() == LookupNamespaceName ||
R.getLookupKind() == LookupObjCProtocolName ||
R.getLookupKind() == LookupLabel)
return false;
// If we're performing qualified name lookup into a dependent class,
// then we are actually looking into a current instantiation. If we have any
// dependent base classes, then we either have to delay lookup until
// template instantiation time (at which point all bases will be available)
// or we have to fail.
if (!InUnqualifiedLookup && LookupRec->isDependentContext() &&
LookupRec->hasAnyDependentBases()) {
return false;
// Perform lookup into our base classes.
DeclarationName Name = R.getLookupName();
unsigned IDNS = R.getIdentifierNamespace();
// Look for this member in our base classes.
auto BaseCallback = [Name, IDNS](const CXXBaseSpecifier *Specifier,
CXXBasePath &Path) -> bool {
CXXRecordDecl *BaseRecord = Specifier->getType()->getAsCXXRecordDecl();
// Drop leading non-matching lookup results from the declaration list so
// we don't need to consider them again below.
for (Path.Decls = BaseRecord->lookup(Name).begin();
Path.Decls != Path.Decls.end(); ++Path.Decls) {
if ((*Path.Decls)->isInIdentifierNamespace(IDNS))
return true;
return false;
CXXBasePaths Paths;
if (!LookupRec->lookupInBases(BaseCallback, Paths))
return false;
// C++ [class.member.lookup]p2:
// [...] If the resulting set of declarations are not all from
// sub-objects of the same type, or the set has a nonstatic member
// and includes members from distinct sub-objects, there is an
// ambiguity and the program is ill-formed. Otherwise that set is
// the result of the lookup.
QualType SubobjectType;
int SubobjectNumber = 0;
AccessSpecifier SubobjectAccess = AS_none;
// Check whether the given lookup result contains only static members.
auto HasOnlyStaticMembers = [&](DeclContext::lookup_iterator Result) {
for (DeclContext::lookup_iterator I = Result, E = I.end(); I != E; ++I)
if ((*I)->isInIdentifierNamespace(IDNS) && (*I)->isCXXInstanceMember())
return false;
return true;
bool TemplateNameLookup = R.isTemplateNameLookup();
// Determine whether two sets of members contain the same members, as
// required by C++ [class.member.lookup]p6.
auto HasSameDeclarations = [&](DeclContext::lookup_iterator A,
DeclContext::lookup_iterator B) {
using Iterator = DeclContextLookupResult::iterator;
using Result = const void *;
auto Next = [&](Iterator &It, Iterator End) -> Result {
while (It != End) {
NamedDecl *ND = *It++;
if (!ND->isInIdentifierNamespace(IDNS))
// C++ [temp.local]p3:
// A lookup that finds an injected-class-name (10.2) can result in
// an ambiguity in certain cases (for example, if it is found in
// more than one base class). If all of the injected-class-names
// that are found refer to specializations of the same class
// template, and if the name is used as a template-name, the
// reference refers to the class template itself and not a
// specialization thereof, and is not ambiguous.
if (TemplateNameLookup)
if (auto *TD = getAsTemplateNameDecl(ND))
ND = TD;
// C++ [class.member.lookup]p3:
// type declarations (including injected-class-names) are replaced by
// the types they designate
if (const TypeDecl *TD = dyn_cast<TypeDecl>(ND->getUnderlyingDecl())) {
QualType T = Context.getTypeDeclType(TD);
return T.getCanonicalType().getAsOpaquePtr();
return ND->getUnderlyingDecl()->getCanonicalDecl();
return nullptr;
// We'll often find the declarations are in the same order. Handle this
// case (and the special case of only one declaration) efficiently.
Iterator AIt = A, BIt = B, AEnd, BEnd;
while (true) {
Result AResult = Next(AIt, AEnd);
Result BResult = Next(BIt, BEnd);
if (!AResult && !BResult)
return true;
if (!AResult || !BResult)
return false;
if (AResult != BResult) {
// Found a mismatch; carefully check both lists, accounting for the
// possibility of declarations appearing more than once.
llvm::SmallDenseMap<Result, bool, 32> AResults;
for (; AResult; AResult = Next(AIt, AEnd))
AResults.insert({AResult, /*FoundInB*/false});
unsigned Found = 0;
for (; BResult; BResult = Next(BIt, BEnd)) {
auto It = AResults.find(BResult);
if (It == AResults.end())
return false;
if (!It->second) {
It->second = true;
return AResults.size() == Found;
for (CXXBasePaths::paths_iterator Path = Paths.begin(), PathEnd = Paths.end();
Path != PathEnd; ++Path) {
const CXXBasePathElement &PathElement = Path->back();
// Pick the best (i.e. most permissive i.e. numerically lowest) access
// across all paths.
SubobjectAccess = std::min(SubobjectAccess, Path->Access);
// Determine whether we're looking at a distinct sub-object or not.
if (SubobjectType.isNull()) {
// This is the first subobject we've looked at. Record its type.
SubobjectType = Context.getCanonicalType(PathElement.Base->getType());
SubobjectNumber = PathElement.SubobjectNumber;
if (SubobjectType !=
Context.getCanonicalType(PathElement.Base->getType())) {
// We found members of the given name in two subobjects of
// different types. If the declaration sets aren't the same, this
// lookup is ambiguous.
// FIXME: The language rule says that this applies irrespective of
// whether the sets contain only static members.
if (HasOnlyStaticMembers(Path->Decls) &&
HasSameDeclarations(Paths.begin()->Decls, Path->Decls))
return true;
// FIXME: This language rule no longer exists. Checking for ambiguous base
// subobjects should be done as part of formation of a class member access
// expression (when converting the object parameter to the member's type).
if (SubobjectNumber != PathElement.SubobjectNumber) {
// We have a different subobject of the same type.
// C++ [class.member.lookup]p5:
// A static member, a nested type or an enumerator defined in
// a base class T can unambiguously be found even if an object
// has more than one base class subobject of type T.
if (HasOnlyStaticMembers(Path->Decls))
// We have found a nonstatic member name in multiple, distinct
// subobjects. Name lookup is ambiguous.
return true;
// Lookup in a base class succeeded; return these results.
for (DeclContext::lookup_iterator I = Paths.front().Decls, E = I.end();
I != E; ++I) {
AccessSpecifier AS = CXXRecordDecl::MergeAccess(SubobjectAccess,
if (NamedDecl *ND = R.getAcceptableDecl(*I))
R.addDecl(ND, AS);
return true;
/// Performs qualified name lookup or special type of lookup for
/// "__super::" scope specifier.
/// This routine is a convenience overload meant to be called from contexts
/// that need to perform a qualified name lookup with an optional C++ scope
/// specifier that might require special kind of lookup.
/// \param R captures both the lookup criteria and any lookup results found.
/// \param LookupCtx The context in which qualified name lookup will
/// search.
/// \param SS An optional C++ scope-specifier.
/// \returns true if lookup succeeded, false if it failed.
bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
CXXScopeSpec &SS) {
auto *NNS = SS.getScopeRep();
if (NNS && NNS->getKind() == NestedNameSpecifier::Super)
return LookupInSuper(R, NNS->getAsRecordDecl());
return LookupQualifiedName(R, LookupCtx);
/// Performs name lookup for a name that was parsed in the
/// source code, and may contain a C++ scope specifier.
/// This routine is a convenience routine meant to be called from
/// contexts that receive a name and an optional C++ scope specifier
/// (e.g., "N::M::x"). It will then perform either qualified or
/// unqualified name lookup (with LookupQualifiedName or LookupName,
/// respectively) on the given name and return those results. It will
/// perform a special type of lookup for "__super::" scope specifier.
/// @param S The scope from which unqualified name lookup will
/// begin.
/// @param SS An optional C++ scope-specifier, e.g., "::N::M".
/// @param EnteringContext Indicates whether we are going to enter the
/// context of the scope-specifier SS (if present).
/// @returns True if any decls were found (but possibly ambiguous)
bool Sema::LookupParsedName(LookupResult &R, Scope *S, CXXScopeSpec *SS,
bool AllowBuiltinCreation, bool EnteringContext) {
if (SS && SS->isInvalid()) {
// When the scope specifier is invalid, don't even look for
// anything.
return false;
if (SS && SS->isSet()) {
NestedNameSpecifier *NNS = SS->getScopeRep();
if (NNS->getKind() == NestedNameSpecifier::Super)
return LookupInSuper(R, NNS->getAsRecordDecl());
if (DeclContext *DC = computeDeclContext(*SS, EnteringContext)) {
// We have resolved the scope specifier to a particular declaration
// contex, and will perform name lookup in that context.
if (!DC->isDependentContext() && RequireCompleteDeclContext(*SS, DC))
return false;
return LookupQualifiedName(R, DC);
// We could not resolve the scope specified to a specific declaration
// context, which means that SS refers to an unknown specialization.
// Name lookup can't find anything in this case.
return false;
// Perform unqualified name lookup starting in the given scope.
return LookupName(R, S, AllowBuiltinCreation);
/// Perform qualified name lookup into all base classes of the given
/// class.
/// \param R captures both the lookup criteria and any lookup results found.
/// \param Class The context in which qualified name lookup will
/// search. Name lookup will search in all base classes merging the results.
/// @returns True if any decls were found (but possibly ambiguous)
bool Sema::LookupInSuper(LookupResult &R, CXXRecordDecl *Class) {
// The access-control rules we use here are essentially the rules for
// doing a lookup in Class that just magically skipped the direct
// members of Class itself. That is, the naming class is Class, and the
// access includes the access of the base.
for (const auto &BaseSpec : Class->bases()) {
CXXRecordDecl *RD = cast<CXXRecordDecl>(
LookupResult Result(*this, R.getLookupNameInfo(), R.getLookupKind());
LookupQualifiedName(Result, RD);
// Copy the lookup results into the target, merging the base's access into
// the path access.
for (auto I = Result.begin(), E = Result.end(); I != E; ++I) {
return !R.empty();
/// Produce a diagnostic describing the ambiguity that resulted
/// from name lookup.
/// \param Result The result of the ambiguous lookup to be diagnosed.
void Sema::DiagnoseAmbiguousLookup(LookupResult &Result) {
assert(Result.isAmbiguous() && "Lookup result must be ambiguous");
DeclarationName Name = Result.getLookupName();
SourceLocation NameLoc = Result.getNameLoc();
SourceRange LookupRange = Result.getContextRange();
switch (Result.getAmbiguityKind()) {
case LookupResult::AmbiguousBaseSubobjects: {
CXXBasePaths *Paths = Result.getBasePaths();
QualType SubobjectType = Paths->front().back().Base->getType();
Diag(NameLoc, diag::err_ambiguous_member_multiple_subobjects)
<< Name << SubobjectType << getAmbiguousPathsDisplayString(*Paths)
<< LookupRange;
DeclContext::lookup_iterator Found = Paths->front().Decls;
while (isa<CXXMethodDecl>(*Found) &&
Diag((*Found)->getLocation(), diag::note_ambiguous_member_found);
case LookupResult::AmbiguousBaseSubobjectTypes: {
Diag(NameLoc, diag::err_ambiguous_member_multiple_subobject_types)
<< Name << LookupRange;
CXXBasePaths *Paths = Result.getBasePaths();
std::set<const NamedDecl *> DeclsPrinted;
for (CXXBasePaths::paths_iterator Path = Paths->begin(),
PathEnd = Paths->end();
Path != PathEnd; ++Path) {
const NamedDecl *D = *Path->Decls;
if (!D->isInIdentifierNamespace(Result.getIdentifierNamespace()))
if (DeclsPrinted.insert(D).second) {
if (const auto *TD = dyn_cast<TypedefNameDecl>(D->getUnderlyingDecl()))
Diag(D->getLocation(), diag::note_ambiguous_member_type_found)
<< TD->getUnderlyingType();
else if (const auto *TD = dyn_cast<TypeDecl>(D->getUnderlyingDecl()))
Diag(D->getLocation(), diag::note_ambiguous_member_type_found)
<< Context.getTypeDeclType(TD);
Diag(D->getLocation(), diag::note_ambiguous_member_found);
case LookupResult::AmbiguousTagHiding: {
Diag(NameLoc, diag::err_ambiguous_tag_hiding) << Name << LookupRange;
llvm::SmallPtrSet<NamedDecl*, 8> TagDecls;
for (auto *D : Result)
if (TagDecl *TD = dyn_cast<TagDecl>(D)) {
Diag(TD->getLocation(), diag::note_hidden_tag);
for (auto *D : Result)
if (!isa<TagDecl>(D))
Diag(D->getLocation(), diag::note_hiding_object);
// For recovery purposes, go ahead and implement the hiding.
LookupResult::Filter F = Result.makeFilter();
while (F.hasNext()) {
if (TagDecls.count(
case LookupResult::AmbiguousReference: {
Diag(NameLoc, diag::err_ambiguous_reference) << Name << LookupRange;
for (auto *D : Result)
Diag(D->getLocation(), diag::note_ambiguous_candidate) << D;
namespace {
struct AssociatedLookup {
AssociatedLookup(Sema &S, SourceLocation InstantiationLoc,
Sema::AssociatedNamespaceSet &Namespaces,
Sema::AssociatedClassSet &Classes)
: S(S), Namespaces(Namespaces), Classes(Classes),
InstantiationLoc(InstantiationLoc) {
bool addClassTransitive(CXXRecordDecl *RD) {
return ClassesTransitive.insert(RD);
Sema &S;
Sema::AssociatedNamespaceSet &Namespaces;
Sema::AssociatedClassSet &Classes;
SourceLocation InstantiationLoc;
Sema::AssociatedClassSet ClassesTransitive;
} // end anonymous namespace
static void
addAssociatedClassesAndNamespaces(AssociatedLookup &Result, QualType T);
// Given the declaration context \param Ctx of a class, class template or
// enumeration, add the associated namespaces to \param Namespaces as described
// in [basic.lookup.argdep]p2.
static void CollectEnclosingNamespace(Sema::AssociatedNamespaceSet &Namespaces,
DeclContext *Ctx) {
// The exact wording has been changed in C++14 as a result of
// CWG 1691 (see also CWG 1690 and CWG 1692). We apply it unconditionally
// to all language versions since it is possible to return a local type
// from a lambda in C++11.
// C++14 [basic.lookup.argdep]p2:
// If T is a class type [...]. Its associated namespaces are the innermost
// enclosing namespaces of its associated classes. [...]
// If T is an enumeration type, its associated namespace is the innermost
// enclosing namespace of its declaration. [...]
// We additionally skip inline namespaces. The innermost non-inline namespace
// contains all names of all its nested inline namespaces anyway, so we can
// replace the entire inline namespace tree with its root.
while (!Ctx->isFileContext() || Ctx->isInlineNamespace())
Ctx = Ctx->getParent();
// Add the associated classes and namespaces for argument-dependent
// lookup that involves a template argument (C++ [basic.lookup.argdep]p2).
static void
addAssociatedClassesAndNamespaces(AssociatedLookup &Result,
const TemplateArgument &Arg) {
// C++ [basic.lookup.argdep]p2, last bullet:
// -- [...] ;
switch (Arg.getKind()) {
case TemplateArgument::Null:
case TemplateArgument::Type:
// [...] the namespaces and classes associated with the types of the
// template arguments provided for template type parameters (excluding
// template template parameters)
addAssociatedClassesAndNamespaces(Result, Arg.getAsType());
case TemplateArgument::Template:
case TemplateArgument::TemplateExpansion: {
// [...] the namespaces in which any template template arguments are
// defined; and the classes in which any member templates used as
// template template arguments are defined.
TemplateName Template = Arg.getAsTemplateOrTemplatePattern();
if (ClassTemplateDecl *ClassTemplate
= dyn_cast<ClassTemplateDecl>(Template.getAsTemplateDecl())) {
DeclContext *Ctx = ClassTemplate->getDeclContext();
if (CXXRecordDecl *EnclosingClass = dyn_cast<CXXRecordDecl>(Ctx))
// Add the associated namespace for this class.
CollectEnclosingNamespace(Result.Namespaces, Ctx);
case TemplateArgument::Declaration:
case TemplateArgument::Integral:
case TemplateArgument::Expression:
case TemplateArgument::NullPtr:
// [Note: non-type template arguments do not contribute to the set of
// associated namespaces. ]
case TemplateArgument::Pack:
for (const auto &P : Arg.pack_elements())
addAssociatedClassesAndNamespaces(Result, P);
// Add the associated classes and namespaces for argument-dependent lookup
// with an argument of class type (C++ [basic.lookup.argdep]p2).
static void
addAssociatedClassesAndNamespaces(AssociatedLookup &Result,
CXXRecordDecl *Class) {
// Just silently ignore anything whose name is __va_list_tag.
if (Class->getDeclName() == Result.S.VAListTagName)
// C++ [basic.lookup.argdep]p2:
// [...]
// -- If T is a class type (including unions), its associated
// classes are: the class itself; the class of which it is a
// member, if any; and its direct and indirect base classes.
// Its associated namespaces are the innermost enclosing
// namespaces of its associated classes.
// Add the class of which it is a member, if any.
DeclContext *Ctx = Class->getDeclContext();
if (CXXRecordDecl *EnclosingClass = dyn_cast<CXXRecordDecl>(Ctx))
// Add the associated namespace for this class.
CollectEnclosingNamespace(Result.Namespaces, Ctx);
// -- If T is a template-id, its associated namespaces and classes are
// the namespace in which the template is defined; for member
// templates, the member template's class; the namespaces and classes
// associated with the types of the template arguments provided for
// template type parameters (excluding template template parameters); the
// namespaces in which any template template arguments are defined; and
// the classes in which any member templates used as template template
// arguments are defined. [Note: non-type template arguments do not
// contribute to the set of associated namespaces. ]
if (ClassTemplateSpecializationDecl *Spec
= dyn_cast<ClassTemplateSpecializationDecl>(Class)) {
DeclContext *Ctx = Spec->getSpecializedTemplate()->getDeclContext();
if (CXXRecordDecl *EnclosingClass = dyn_cast<CXXRecordDecl>(Ctx))
// Add the associated namespace for this class.
CollectEnclosingNamespace(Result.Namespaces, Ctx);
const TemplateArgumentList &TemplateArgs = Spec->getTemplateArgs();
for (unsigned I = 0, N = TemplateArgs.size(); I != N; ++I)
addAssociatedClassesAndNamespaces(Result, TemplateArgs[I]);
// Add the class itself. If we've already transitively visited this class,
// we don't need to visit base classes.
if (!Result.addClassTransitive(Class))
// Only recurse into base classes for complete types.
if (!Result.S.isCompleteType(Result.InstantiationLoc,
// Add direct and indirect base classes along with their associated
// namespaces.
SmallVector<CXXRecordDecl *, 32> Bases;
while (!Bases.empty()) {
// Pop this class off the stack.
Class = Bases.pop_back_val();
// Visit the base classes.
for (const auto &Base : Class->bases()) {
const RecordType *BaseType = Base.getType()->getAs<RecordType>();
// In dependent contexts, we do ADL twice, and the first time around,
// the base type might be a dependent TemplateSpecializationType, or a
// TemplateTypeParmType. If that happens, simply ignore it.
// FIXME: If we want to support export, we probably need to add the
// namespace of the template in a TemplateSpecializationType, or even
// the classes and namespaces of known non-dependent arguments.
if (!BaseType)
CXXRecordDecl *BaseDecl = cast<CXXRecordDecl>(BaseType->getDecl());
if (Result.addClassTransitive(BaseDecl)) {
// Find the associated namespace for this base class.
DeclContext *BaseCtx = BaseDecl->getDeclContext();
CollectEnclosingNamespace(Result.Namespaces, BaseCtx);
// Make sure we visit the bases of this base class.
if (BaseDecl->bases_begin() != BaseDecl->bases_end())
// Add the associated classes and namespaces for
// argument-dependent lookup with an argument of type T
// (C++ [basic.lookup.koenig]p2).
static void
addAssociatedClassesAndNamespaces(AssociatedLookup &Result, QualType Ty) {
// C++ [basic.lookup.koenig]p2:
// For each argument type T in the function call, there is a set
// of zero or more associated namespaces and a set of zero or more
// associated classes to be considered. The sets of namespaces and
// classes is determined entirely by the types of the function
// arguments (and the namespace of any template template
// argument). Typedef names and using-declarations used to specify
// the types do not contribute to this set. The sets of namespaces
// and classes are determined in the following way:
SmallVector<const Type *, 16> Queue;
const Type *T = Ty->getCanonicalTypeInternal().getTypePtr();
while (true) {
switch (T->getTypeClass()) {
#define TYPE(Class, Base)
#define DEPENDENT_TYPE(Class, Base) case Type::Class:
#define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
#define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Class, Base) case Type::Class:
#define ABSTRACT_TYPE(Class, Base)
#include "clang/AST/"
// T is canonical. We can also ignore dependent types because
// we don't need to do ADL at the definition point, but if we
// wanted to implement template export (or if we find some other
// use for associated classes and namespaces...) this would be
// wrong.
// -- If T is a pointer to U or an array of U, its associated
// namespaces and classes are those associated with U.
case Type::Pointer:
T = cast<PointerType>(T)->getPointeeType().getTypePtr();
case Type::ConstantArray:
case Type::IncompleteArray:
case Type::VariableArray:
T = cast<ArrayType>(T)->getElementType().getTypePtr();
// -- If T is a fundamental type, its associated sets of
// namespaces and classes are b