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//===--- SemaModule.cpp - Semantic Analysis for Modules -------------------===//
// 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 semantic analysis for modules (C++ modules syntax,
// Objective-C modules syntax, and Clang header modules).
#include "clang/AST/ASTConsumer.h"
#include "clang/Lex/HeaderSearch.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/SemaInternal.h"
using namespace clang;
using namespace sema;
static void checkModuleImportContext(Sema &S, Module *M,
SourceLocation ImportLoc, DeclContext *DC,
bool FromInclude = false) {
SourceLocation ExternCLoc;
if (auto *LSD = dyn_cast<LinkageSpecDecl>(DC)) {
switch (LSD->getLanguage()) {
case LinkageSpecDecl::lang_c:
if (ExternCLoc.isInvalid())
ExternCLoc = LSD->getBeginLoc();
case LinkageSpecDecl::lang_cxx:
DC = LSD->getParent();
while (isa<LinkageSpecDecl>(DC) || isa<ExportDecl>(DC))
DC = DC->getParent();
if (!isa<TranslationUnitDecl>(DC)) {
S.Diag(ImportLoc, (FromInclude && S.isModuleVisible(M))
? diag::ext_module_import_not_at_top_level_noop
: diag::err_module_import_not_at_top_level_fatal)
<< M->getFullModuleName() << DC;
<< DC;
} else if (!M->IsExternC && ExternCLoc.isValid()) {
S.Diag(ImportLoc, diag::ext_module_import_in_extern_c)
<< M->getFullModuleName();
S.Diag(ExternCLoc, diag::note_extern_c_begins_here);
// We represent the primary and partition names as 'Paths' which are sections
// of the hierarchical access path for a clang module. However for C++20
// the periods in a name are just another character, and we will need to
// flatten them into a string.
static std::string stringFromPath(ModuleIdPath Path) {
std::string Name;
if (Path.empty())
return Name;
for (auto &Piece : Path) {
if (!Name.empty())
Name += ".";
Name += Piece.first->getName();
return Name;
Sema::ActOnGlobalModuleFragmentDecl(SourceLocation ModuleLoc) {
if (!ModuleScopes.empty() &&
ModuleScopes.back().Module->Kind == Module::GlobalModuleFragment) {
// Under -std=c++2a -fmodules-ts, we can find an explicit 'module;' after
// already implicitly entering the global module fragment. That's OK.
assert(getLangOpts().CPlusPlusModules && getLangOpts().ModulesTS &&
"unexpectedly encountered multiple global module fragment decls");
ModuleScopes.back().BeginLoc = ModuleLoc;
return nullptr;
// We start in the global module; all those declarations are implicitly
// module-private (though they do not have module linkage).
Module *GlobalModule =
PushGlobalModuleFragment(ModuleLoc, /*IsImplicit=*/false);
// All declarations created from now on are owned by the global module.
auto *TU = Context.getTranslationUnitDecl();
// FIXME: Consider creating an explicit representation of this declaration.
return nullptr;
void Sema::HandleStartOfHeaderUnit() {
assert(getLangOpts().CPlusPlusModules &&
"Header units are only valid for C++20 modules");
SourceLocation StartOfTU =
StringRef HUName = getLangOpts().CurrentModule;
if (HUName.empty()) {
HUName = SourceMgr.getFileEntryForID(SourceMgr.getMainFileID())->getName();
const_cast<LangOptions &>(getLangOpts()).CurrentModule = HUName.str();
// TODO: Make the C++20 header lookup independent.
// When the input is pre-processed source, we need a file ref to the original
// file for the header map.
auto F = SourceMgr.getFileManager().getFile(HUName);
// For the sake of error recovery (if someone has moved the original header
// after creating the pre-processed output) fall back to obtaining the file
// ref for the input file, which must be present.
if (!F)
F = SourceMgr.getFileEntryForID(SourceMgr.getMainFileID());
assert(F && "failed to find the header unit source?");
Module::Header H{HUName.str(), HUName.str(), *F};
auto &Map = PP.getHeaderSearchInfo().getModuleMap();
Module *Mod = Map.createHeaderUnit(StartOfTU, HUName, H);
assert(Mod && "module creation should not fail");
ModuleScopes.push_back({}); // No GMF
ModuleScopes.back().BeginLoc = StartOfTU;
ModuleScopes.back().Module = Mod;
ModuleScopes.back().ModuleInterface = true;
ModuleScopes.back().IsPartition = false;
VisibleModules.setVisible(Mod, StartOfTU);
// From now on, we have an owning module for all declarations we see.
// All of these are implicitly exported.
auto *TU = Context.getTranslationUnitDecl();
Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
ModuleDeclKind MDK, ModuleIdPath Path,
ModuleIdPath Partition, ModuleImportState &ImportState) {
assert((getLangOpts().ModulesTS || getLangOpts().CPlusPlusModules) &&
"should only have module decl in Modules TS or C++20");
bool IsFirstDecl = ImportState == ModuleImportState::FirstDecl;
bool SeenGMF = ImportState == ModuleImportState::GlobalFragment;
// If any of the steps here fail, we count that as invalidating C++20
// module state;
ImportState = ModuleImportState::NotACXX20Module;
bool IsPartition = !Partition.empty();
if (IsPartition)
switch (MDK) {
case ModuleDeclKind::Implementation:
MDK = ModuleDeclKind::PartitionImplementation;
case ModuleDeclKind::Interface:
MDK = ModuleDeclKind::PartitionInterface;
llvm_unreachable("how did we get a partition type set?");
// A (non-partition) module implementation unit requires that we are not
// compiling a module of any kind. A partition implementation emits an
// interface (and the AST for the implementation), which will subsequently
// be consumed to emit a binary.
// A module interface unit requires that we are not compiling a module map.
switch (getLangOpts().getCompilingModule()) {
case LangOptions::CMK_None:
// It's OK to compile a module interface as a normal translation unit.
case LangOptions::CMK_ModuleInterface:
if (MDK != ModuleDeclKind::Implementation)
// We were asked to compile a module interface unit but this is a module
// implementation unit.
Diag(ModuleLoc, diag::err_module_interface_implementation_mismatch)
<< FixItHint::CreateInsertion(ModuleLoc, "export ");
MDK = ModuleDeclKind::Interface;
case LangOptions::CMK_ModuleMap:
Diag(ModuleLoc, diag::err_module_decl_in_module_map_module);
return nullptr;
case LangOptions::CMK_HeaderModule:
case LangOptions::CMK_HeaderUnit:
Diag(ModuleLoc, diag::err_module_decl_in_header_module);
return nullptr;
assert(ModuleScopes.size() <= 1 && "expected to be at global module scope");
// FIXME: Most of this work should be done by the preprocessor rather than
// here, in order to support macro import.
// Only one module-declaration is permitted per source file.
if (!ModuleScopes.empty() &&
ModuleScopes.back().Module->isModulePurview()) {
Diag(ModuleLoc, diag::err_module_redeclaration);
return nullptr;
// Find the global module fragment we're adopting into this module, if any.
Module *GlobalModuleFragment = nullptr;
if (!ModuleScopes.empty() &&
ModuleScopes.back().Module->Kind == Module::GlobalModuleFragment)
GlobalModuleFragment = ModuleScopes.back().Module;
assert((!getLangOpts().CPlusPlusModules || getLangOpts().ModulesTS ||
SeenGMF == (bool)GlobalModuleFragment) &&
"mismatched global module state");
// In C++20, the module-declaration must be the first declaration if there
// is no global module fragment.
if (getLangOpts().CPlusPlusModules && !IsFirstDecl && !SeenGMF) {
Diag(ModuleLoc, diag::err_module_decl_not_at_start);
SourceLocation BeginLoc =
? SourceMgr.getLocForStartOfFile(SourceMgr.getMainFileID())
: ModuleScopes.back().BeginLoc;
if (BeginLoc.isValid()) {
Diag(BeginLoc, diag::note_global_module_introducer_missing)
<< FixItHint::CreateInsertion(BeginLoc, "module;\n");
// Flatten the dots in a module name. Unlike Clang's hierarchical module map
// modules, the dots here are just another character that can appear in a
// module name.
std::string ModuleName = stringFromPath(Path);
if (IsPartition) {
ModuleName += ":";
ModuleName += stringFromPath(Partition);
// If a module name was explicitly specified on the command line, it must be
// correct.
if (!getLangOpts().CurrentModule.empty() &&
getLangOpts().CurrentModule != ModuleName) {
Diag(Path.front().second, diag::err_current_module_name_mismatch)
<< SourceRange(Path.front().second, IsPartition
? Partition.back().second
: Path.back().second)
<< getLangOpts().CurrentModule;
return nullptr;
const_cast<LangOptions&>(getLangOpts()).CurrentModule = ModuleName;
auto &Map = PP.getHeaderSearchInfo().getModuleMap();
Module *Mod;
switch (MDK) {
case ModuleDeclKind::Interface:
case ModuleDeclKind::PartitionInterface: {
// We can't have parsed or imported a definition of this module or parsed a
// module map defining it already.
if (auto *M = Map.findModule(ModuleName)) {
Diag(Path[0].second, diag::err_module_redefinition) << ModuleName;
if (M->DefinitionLoc.isValid())
Diag(M->DefinitionLoc, diag::note_prev_module_definition);
else if (Optional<FileEntryRef> FE = M->getASTFile())
Diag(M->DefinitionLoc, diag::note_prev_module_definition_from_ast_file)
<< FE->getName();
Mod = M;
// Create a Module for the module that we're defining.
Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
if (MDK == ModuleDeclKind::PartitionInterface)
Mod->Kind = Module::ModulePartitionInterface;
assert(Mod && "module creation should not fail");
case ModuleDeclKind::Implementation: {
std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc(
PP.getIdentifierInfo(ModuleName), Path[0].second);
// C++20 A module-declaration that contains neither an export-
// keyword nor a module-partition implicitly imports the primary
// module interface unit of the module as if by a module-import-
// declaration.
Mod = getModuleLoader().loadModule(ModuleLoc, {ModuleNameLoc},
if (!Mod) {
Diag(ModuleLoc, diag::err_module_not_defined) << ModuleName;
// Create an empty module interface unit for error recovery.
Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
} break;
case ModuleDeclKind::PartitionImplementation:
// Create an interface, but note that it is an implementation
// unit.
Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
Mod->Kind = Module::ModulePartitionImplementation;
if (!GlobalModuleFragment) {
if (getLangOpts().ModulesLocalVisibility)
ModuleScopes.back().OuterVisibleModules = std::move(VisibleModules);
} else {
// We're done with the global module fragment now.
// Switch from the global module fragment (if any) to the named module.
ModuleScopes.back().BeginLoc = StartLoc;
ModuleScopes.back().Module = Mod;
ModuleScopes.back().ModuleInterface = MDK != ModuleDeclKind::Implementation;
ModuleScopes.back().IsPartition = IsPartition;
VisibleModules.setVisible(Mod, ModuleLoc);
// From now on, we have an owning module for all declarations we see.
// However, those declarations are module-private unless explicitly
// exported.
auto *TU = Context.getTranslationUnitDecl();
// We are in the module purview, but before any other (non import)
// statements, so imports are allowed.
ImportState = ModuleImportState::ImportAllowed;
// FIXME: Create a ModuleDecl.
return nullptr;
Sema::ActOnPrivateModuleFragmentDecl(SourceLocation ModuleLoc,
SourceLocation PrivateLoc) {
// C++20 []/2:
// A private-module-fragment shall appear only in a primary module
// interface unit.
switch (ModuleScopes.empty() ? Module::GlobalModuleFragment
: ModuleScopes.back().Module->Kind) {
case Module::ModuleMapModule:
case Module::GlobalModuleFragment:
case Module::ModulePartitionImplementation:
case Module::ModulePartitionInterface:
case Module::ModuleHeaderUnit:
Diag(PrivateLoc, diag::err_private_module_fragment_not_module);
return nullptr;
case Module::PrivateModuleFragment:
Diag(PrivateLoc, diag::err_private_module_fragment_redefined);
Diag(ModuleScopes.back().BeginLoc, diag::note_previous_definition);
return nullptr;
case Module::ModuleInterfaceUnit:
if (!ModuleScopes.back().ModuleInterface) {
Diag(PrivateLoc, diag::err_private_module_fragment_not_module_interface);
<< FixItHint::CreateInsertion(ModuleScopes.back().BeginLoc, "export ");
return nullptr;
// FIXME: Check this isn't a module interface partition.
// FIXME: Check that this translation unit does not import any partitions;
// such imports would violate []/2's "shall be the only module unit"
// restriction.
// We've finished the public fragment of the translation unit.
auto &Map = PP.getHeaderSearchInfo().getModuleMap();
Module *PrivateModuleFragment =
ModuleScopes.back().Module, PrivateLoc);
assert(PrivateModuleFragment && "module creation should not fail");
// Enter the scope of the private module fragment.
ModuleScopes.back().BeginLoc = ModuleLoc;
ModuleScopes.back().Module = PrivateModuleFragment;
ModuleScopes.back().ModuleInterface = true;
VisibleModules.setVisible(PrivateModuleFragment, ModuleLoc);
// All declarations created from now on are scoped to the private module
// fragment (and are neither visible nor reachable in importers of the module
// interface).
auto *TU = Context.getTranslationUnitDecl();
// FIXME: Consider creating an explicit representation of this declaration.
return nullptr;
DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
SourceLocation ExportLoc,
SourceLocation ImportLoc, ModuleIdPath Path,
bool IsPartition) {
bool Cxx20Mode = getLangOpts().CPlusPlusModules || getLangOpts().ModulesTS;
assert((!IsPartition || Cxx20Mode) && "partition seen in non-C++20 code?");
// For a C++20 module name, flatten into a single identifier with the source
// location of the first component.
std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc;
std::string ModuleName;
if (IsPartition) {
// We already checked that we are in a module purview in the parser.
assert(!ModuleScopes.empty() && "in a module purview, but no module?");
Module *NamedMod = ModuleScopes.back().Module;
// If we are importing into a partition, find the owning named module,
// otherwise, the name of the importing named module.
ModuleName = NamedMod->getPrimaryModuleInterfaceName().str();
ModuleName += ":";
ModuleName += stringFromPath(Path);
ModuleNameLoc = {PP.getIdentifierInfo(ModuleName), Path[0].second};
Path = ModuleIdPath(ModuleNameLoc);
} else if (Cxx20Mode) {
ModuleName = stringFromPath(Path);
ModuleNameLoc = {PP.getIdentifierInfo(ModuleName), Path[0].second};
Path = ModuleIdPath(ModuleNameLoc);
// Diagnose self-import before attempting a load.
// [module.import]/9
// A module implementation unit of a module M that is not a module partition
// shall not contain a module-import-declaration nominating M.
// (for an implementation, the module interface is imported implicitly,
// but that's handled in the module decl code).
if (getLangOpts().CPlusPlusModules && isCurrentModulePurview() &&
getCurrentModule()->Name == ModuleName) {
Diag(ImportLoc, diag::err_module_self_import_cxx20)
<< ModuleName << !ModuleScopes.back().ModuleInterface;
return true;
Module *Mod = getModuleLoader().loadModule(
ImportLoc, Path, Module::AllVisible, /*IsInclusionDirective=*/false);
if (!Mod)
return true;
return ActOnModuleImport(StartLoc, ExportLoc, ImportLoc, Mod, Path);
/// Determine whether \p D is lexically within an export-declaration.
static const ExportDecl *getEnclosingExportDecl(const Decl *D) {
for (auto *DC = D->getLexicalDeclContext(); DC; DC = DC->getLexicalParent())
if (auto *ED = dyn_cast<ExportDecl>(DC))
return ED;
return nullptr;
DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
SourceLocation ExportLoc,
SourceLocation ImportLoc, Module *Mod,
ModuleIdPath Path) {
VisibleModules.setVisible(Mod, ImportLoc);
checkModuleImportContext(*this, Mod, ImportLoc, CurContext);
// FIXME: we should support importing a submodule within a different submodule
// of the same top-level module. Until we do, make it an error rather than
// silently ignoring the import.
// FIXME: Should we warn on a redundant import of the current module?
if (Mod->getTopLevelModuleName() == getLangOpts().CurrentModule &&
(getLangOpts().isCompilingModule() || !getLangOpts().ModulesTS)) {
Diag(ImportLoc, getLangOpts().isCompilingModule()
? diag::err_module_self_import
: diag::err_module_import_in_implementation)
<< Mod->getFullModuleName() << getLangOpts().CurrentModule;
SmallVector<SourceLocation, 2> IdentifierLocs;
if (Path.empty()) {
// If this was a header import, pad out with dummy locations.
// FIXME: Pass in and use the location of the header-name token in this
// case.
for (Module *ModCheck = Mod; ModCheck; ModCheck = ModCheck->Parent)
} else if (getLangOpts().CPlusPlusModules && !Mod->Parent) {
// A single identifier for the whole name.
} else {
Module *ModCheck = Mod;
for (unsigned I = 0, N = Path.size(); I != N; ++I) {
// If we've run out of module parents, just drop the remaining
// identifiers. We need the length to be consistent.
if (!ModCheck)
ModCheck = ModCheck->Parent;
ImportDecl *Import = ImportDecl::Create(Context, CurContext, StartLoc,
Mod, IdentifierLocs);
// Sequence initialization of the imported module before that of the current
// module, if any.
if (!ModuleScopes.empty())
Context.addModuleInitializer(ModuleScopes.back().Module, Import);
// A module (partition) implementation unit shall not be exported.
if (getLangOpts().CPlusPlusModules && ExportLoc.isValid() &&
Mod->Kind == Module::ModuleKind::ModulePartitionImplementation) {
Diag(ExportLoc, diag::err_export_partition_impl)
<< SourceRange(ExportLoc, Path.back().second);
} else if (!ModuleScopes.empty() &&
(ModuleScopes.back().ModuleInterface ||
(getLangOpts().CPlusPlusModules &&
ModuleScopes.back().Module->isGlobalModule()))) {
assert((!ModuleScopes.back().Module->isGlobalModule() ||
Mod->Kind == Module::ModuleKind::ModuleHeaderUnit) &&
"should only be importing a header unit into the GMF");
// Re-export the module if the imported module is exported.
// Note that we don't need to add re-exported module to Imports field
// since `Exports` implies the module is imported already.
if (ExportLoc.isValid() || getEnclosingExportDecl(Import))
getCurrentModule()->Exports.emplace_back(Mod, false);
} else if (ExportLoc.isValid()) {
// [module.interface]p1:
// An export-declaration shall inhabit a namespace scope and appear in the
// purview of a module interface unit.
Diag(ExportLoc, diag::err_export_not_in_module_interface)
<< (!ModuleScopes.empty() &&
} else if (getLangOpts().isCompilingModule()) {
Module *ThisModule = PP.getHeaderSearchInfo().lookupModule(
getLangOpts().CurrentModule, ExportLoc, false, false);
assert(ThisModule && "was expecting a module if building one");
// In some cases we need to know if an entity was present in a directly-
// imported module (as opposed to a transitive import). This avoids
// searching both Imports and Exports.
return Import;
void Sema::ActOnModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
BuildModuleInclude(DirectiveLoc, Mod);
void Sema::BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
// Determine whether we're in the #include buffer for a module. The #includes
// in that buffer do not qualify as module imports; they're just an
// implementation detail of us building the module.
// FIXME: Should we even get ActOnModuleInclude calls for those?
bool IsInModuleIncludes =
TUKind == TU_Module &&
bool ShouldAddImport = !IsInModuleIncludes;
// If this module import was due to an inclusion directive, create an
// implicit import declaration to capture it in the AST.
if (ShouldAddImport) {
TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
DirectiveLoc, Mod,
if (!ModuleScopes.empty())
Context.addModuleInitializer(ModuleScopes.back().Module, ImportD);
getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, DirectiveLoc);
VisibleModules.setVisible(Mod, DirectiveLoc);
if (getLangOpts().isCompilingModule()) {
Module *ThisModule = PP.getHeaderSearchInfo().lookupModule(
getLangOpts().CurrentModule, DirectiveLoc, false, false);
assert(ThisModule && "was expecting a module if building one");
void Sema::ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod) {
checkModuleImportContext(*this, Mod, DirectiveLoc, CurContext, true);
ModuleScopes.back().Module = Mod;
if (getLangOpts().ModulesLocalVisibility)
ModuleScopes.back().OuterVisibleModules = std::move(VisibleModules);
VisibleModules.setVisible(Mod, DirectiveLoc);
// The enclosing context is now part of this module.
// FIXME: Consider creating a child DeclContext to hold the entities
// lexically within the module.
if (getLangOpts().trackLocalOwningModule()) {
for (auto *DC = CurContext; DC; DC = DC->getLexicalParent()) {
? Decl::ModuleOwnershipKind::VisibleWhenImported
: Decl::ModuleOwnershipKind::Visible);
void Sema::ActOnModuleEnd(SourceLocation EomLoc, Module *Mod) {
if (getLangOpts().ModulesLocalVisibility) {
VisibleModules = std::move(ModuleScopes.back().OuterVisibleModules);
// Leaving a module hides namespace names, so our visible namespace cache
// is now out of date.
assert(!ModuleScopes.empty() && ModuleScopes.back().Module == Mod &&
"left the wrong module scope");
// We got to the end of processing a local module. Create an
// ImportDecl as we would for an imported module.
FileID File = getSourceManager().getFileID(EomLoc);
SourceLocation DirectiveLoc;
if (EomLoc == getSourceManager().getLocForEndOfFile(File)) {
// We reached the end of a #included module header. Use the #include loc.
assert(File != getSourceManager().getMainFileID() &&
"end of submodule in main source file");
DirectiveLoc = getSourceManager().getIncludeLoc(File);
} else {
// We reached an EOM pragma. Use the pragma location.
DirectiveLoc = EomLoc;
BuildModuleInclude(DirectiveLoc, Mod);
// Any further declarations are in whatever module we returned to.
if (getLangOpts().trackLocalOwningModule()) {
// The parser guarantees that this is the same context that we entered
// the module within.
for (auto *DC = CurContext; DC; DC = DC->getLexicalParent()) {
if (!getCurrentModule())
void Sema::createImplicitModuleImportForErrorRecovery(SourceLocation Loc,
Module *Mod) {
// Bail if we're not allowed to implicitly import a module here.
if (isSFINAEContext() || !getLangOpts().ModulesErrorRecovery ||
// Create the implicit import declaration.
TranslationUnitDecl *TU = getASTContext().getTranslationUnitDecl();
ImportDecl *ImportD = ImportDecl::CreateImplicit(getASTContext(), TU,
Loc, Mod, Loc);
// Make the module visible.
getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, Loc);
VisibleModules.setVisible(Mod, Loc);
/// We have parsed the start of an export declaration, including the '{'
/// (if present).
Decl *Sema::ActOnStartExportDecl(Scope *S, SourceLocation ExportLoc,
SourceLocation LBraceLoc) {
ExportDecl *D = ExportDecl::Create(Context, CurContext, ExportLoc);
// Set this temporarily so we know the export-declaration was braced.
PushDeclContext(S, D);
// C++2a [module.interface]p1:
// An export-declaration shall appear only [...] in the purview of a module
// interface unit. An export-declaration shall not appear directly or
// indirectly within [...] a private-module-fragment.
if (ModuleScopes.empty() || !ModuleScopes.back().Module->isModulePurview()) {
Diag(ExportLoc, diag::err_export_not_in_module_interface) << 0;
return D;
} else if (!ModuleScopes.back().ModuleInterface) {
Diag(ExportLoc, diag::err_export_not_in_module_interface) << 1;
<< FixItHint::CreateInsertion(ModuleScopes.back().BeginLoc, "export ");
return D;
} else if (ModuleScopes.back().Module->Kind ==
Module::PrivateModuleFragment) {
Diag(ExportLoc, diag::err_export_in_private_module_fragment);
Diag(ModuleScopes.back().BeginLoc, diag::note_private_module_fragment);
return D;
for (const DeclContext *DC = CurContext; DC; DC = DC->getLexicalParent()) {
if (const auto *ND = dyn_cast<NamespaceDecl>(DC)) {
// An export-declaration shall not appear directly or indirectly within
// an unnamed namespace [...]
if (ND->isAnonymousNamespace()) {
Diag(ExportLoc, diag::err_export_within_anonymous_namespace);
Diag(ND->getLocation(), diag::note_anonymous_namespace);
// Don't diagnose internal-linkage declarations in this region.
return D;
// A declaration is exported if it is [...] a namespace-definition
// that contains an exported declaration.
// Defer exporting the namespace until after we leave it, in order to
// avoid marking all subsequent declarations in the namespace as exported.
if (!DeferredExportedNamespaces.insert(ND).second)
// [...] its declaration or declaration-seq shall not contain an
// export-declaration.
if (auto *ED = getEnclosingExportDecl(D)) {
Diag(ExportLoc, diag::err_export_within_export);
if (ED->hasBraces())
Diag(ED->getLocation(), diag::note_export);
return D;
return D;
static bool checkExportedDeclContext(Sema &S, DeclContext *DC,
SourceLocation BlockStart);
namespace {
enum class UnnamedDeclKind {
static llvm::Optional<UnnamedDeclKind> getUnnamedDeclKind(Decl *D) {
if (isa<EmptyDecl>(D))
return UnnamedDeclKind::Empty;
if (isa<StaticAssertDecl>(D))
return UnnamedDeclKind::StaticAssert;
if (isa<FileScopeAsmDecl>(D))
return UnnamedDeclKind::Asm;
if (isa<UsingDirectiveDecl>(D))
return UnnamedDeclKind::UsingDirective;
// Everything else either introduces one or more names or is ill-formed.
return llvm::None;
unsigned getUnnamedDeclDiag(UnnamedDeclKind UDK, bool InBlock) {
switch (UDK) {
case UnnamedDeclKind::Empty:
case UnnamedDeclKind::StaticAssert:
// Allow empty-declarations and static_asserts in an export block as an
// extension.
return InBlock ? diag::ext_export_no_name_block : diag::err_export_no_name;
case UnnamedDeclKind::UsingDirective:
// Allow exporting using-directives as an extension.
return diag::ext_export_using_directive;
case UnnamedDeclKind::Namespace:
// Anonymous namespace with no content.
return diag::introduces_no_names;
case UnnamedDeclKind::Context:
// Allow exporting DeclContexts that transitively contain no declarations
// as an extension.
return diag::ext_export_no_names;
case UnnamedDeclKind::Asm:
return diag::err_export_no_name;
llvm_unreachable("unknown kind");
static void diagExportedUnnamedDecl(Sema &S, UnnamedDeclKind UDK, Decl *D,
SourceLocation BlockStart) {
S.Diag(D->getLocation(), getUnnamedDeclDiag(UDK, BlockStart.isValid()))
<< (unsigned)UDK;
if (BlockStart.isValid())
S.Diag(BlockStart, diag::note_export);
/// Check that it's valid to export \p D.
static bool checkExportedDecl(Sema &S, Decl *D, SourceLocation BlockStart) {
// C++2a [module.interface]p3:
// An exported declaration shall declare at least one name
if (auto UDK = getUnnamedDeclKind(D))
diagExportedUnnamedDecl(S, *UDK, D, BlockStart);
// [...] shall not declare a name with internal linkage.
bool HasName = false;
if (auto *ND = dyn_cast<NamedDecl>(D)) {
// Don't diagnose anonymous union objects; we'll diagnose their members
// instead.
HasName = (bool)ND->getDeclName();
if (HasName && ND->getFormalLinkage() == InternalLinkage) {
S.Diag(ND->getLocation(), diag::err_export_internal) << ND;
if (BlockStart.isValid())
S.Diag(BlockStart, diag::note_export);
// C++2a [module.interface]p5:
// all entities to which all of the using-declarators ultimately refer
// shall have been introduced with a name having external linkage
if (auto *USD = dyn_cast<UsingShadowDecl>(D)) {
NamedDecl *Target = USD->getUnderlyingDecl();
Linkage Lk = Target->getFormalLinkage();
if (Lk == InternalLinkage || Lk == ModuleLinkage) {
S.Diag(USD->getLocation(), diag::err_export_using_internal)
<< (Lk == InternalLinkage ? 0 : 1) << Target;
S.Diag(Target->getLocation(), diag::note_using_decl_target);
if (BlockStart.isValid())
S.Diag(BlockStart, diag::note_export);
// Recurse into namespace-scope DeclContexts. (Only namespace-scope
// declarations are exported.).
if (auto *DC = dyn_cast<DeclContext>(D)) {
if (isa<NamespaceDecl>(D) && DC->decls().empty()) {
if (!HasName)
// We don't allow an empty anonymous namespace (we don't allow decls
// in them either, but that's handled in the recursion).
diagExportedUnnamedDecl(S, UnnamedDeclKind::Namespace, D, BlockStart);
// We allow an empty named namespace decl.
} else if (DC->getRedeclContext()->isFileContext() && !isa<EnumDecl>(D))
return checkExportedDeclContext(S, DC, BlockStart);
return false;
/// Check that it's valid to export all the declarations in \p DC.
static bool checkExportedDeclContext(Sema &S, DeclContext *DC,
SourceLocation BlockStart) {
bool AllUnnamed = true;
for (auto *D : DC->decls())
AllUnnamed &= checkExportedDecl(S, D, BlockStart);
return AllUnnamed;
/// Complete the definition of an export declaration.
Decl *Sema::ActOnFinishExportDecl(Scope *S, Decl *D, SourceLocation RBraceLoc) {
auto *ED = cast<ExportDecl>(D);
if (RBraceLoc.isValid())
if (!D->isInvalidDecl()) {
SourceLocation BlockStart =
ED->hasBraces() ? ED->getBeginLoc() : SourceLocation();
for (auto *Child : ED->decls()) {
if (checkExportedDecl(*this, Child, BlockStart)) {
// If a top-level child is a linkage-spec declaration, it might contain
// no declarations (transitively), in which case it's ill-formed.
diagExportedUnnamedDecl(*this, UnnamedDeclKind::Context, Child,
return D;
Module *Sema::PushGlobalModuleFragment(SourceLocation BeginLoc,
bool IsImplicit) {
// We shouldn't create new global module fragment if there is already
// one.
if (!GlobalModuleFragment) {
ModuleMap &Map = PP.getHeaderSearchInfo().getModuleMap();
GlobalModuleFragment = Map.createGlobalModuleFragmentForModuleUnit(
BeginLoc, getCurrentModule());
assert(GlobalModuleFragment && "module creation should not fail");
// Enter the scope of the global module.
ModuleScopes.push_back({BeginLoc, GlobalModuleFragment,
VisibleModules.setVisible(GlobalModuleFragment, BeginLoc);
return GlobalModuleFragment;
void Sema::PopGlobalModuleFragment() {
assert(!ModuleScopes.empty() && getCurrentModule()->isGlobalModule() &&
"left the wrong module scope, which is not global module fragment");