SemaModule.cpp

Go to the documentation of this file.

//===--- SemaModule.cpp - Semantic Analysis for Modules -------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt 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/AST/ASTMutationListener.h"
#include "clang/Lex/HeaderSearch.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/SemaInternal.h"
#include "llvm/ADT/StringExtras.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 LinkageSpecLanguageIDs::C:
      if (ExternCLoc.isInvalid())
        ExternCLoc = LSD->getBeginLoc();
      break;
    case LinkageSpecLanguageIDs::CXX:
      break;
    }
    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;
    S.Diag(cast<Decl>(DC)->getBeginLoc(),
           diag::note_module_import_not_at_top_level)
        << 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;
}
 
/// Helper function for makeTransitiveImportsVisible to decide whether
/// the \param Imported module unit is in the same module with the \param
/// CurrentModule.
/// \param FoundPrimaryModuleInterface is a helper parameter to record the
/// primary module interface unit corresponding to the module \param
/// CurrentModule. Since currently it is expensive to decide whether two module
/// units come from the same module by comparing the module name.
static bool
isImportingModuleUnitFromSameModule(ASTContext &Ctx, Module *Imported,
                                    Module *CurrentModule,
                                    Module *&FoundPrimaryModuleInterface) {
  if (!Imported->isNamedModule())
    return false;
 
  // The a partition unit we're importing must be in the same module of the
  // current module.
  if (Imported->isModulePartition())
    return true;
 
  // If we found the primary module interface during the search process, we can
  // return quickly to avoid expensive string comparison.
  if (FoundPrimaryModuleInterface)
    return Imported == FoundPrimaryModuleInterface;
 
  if (!CurrentModule)
    return false;
 
  // Then the imported module must be a primary module interface unit.  It
  // is only allowed to import the primary module interface unit from the same
  // module in the implementation unit and the implementation partition unit.
 
  // Since we'll handle implementation unit above. We can only care
  // about the implementation partition unit here.
  if (!CurrentModule->isModulePartitionImplementation())
    return false;
 
  if (Ctx.isInSameModule(Imported, CurrentModule)) {
    assert(!FoundPrimaryModuleInterface ||
           FoundPrimaryModuleInterface == Imported);
    FoundPrimaryModuleInterface = Imported;
    return true;
  }
 
  return false;
}
 
/// [module.import]p7:
///   Additionally, when a module-import-declaration in a module unit of some
///   module M imports another module unit U of M, it also imports all
///   translation units imported by non-exported module-import-declarations in
///   the module unit purview of U. These rules can in turn lead to the
///   importation of yet more translation units.
static void
makeTransitiveImportsVisible(ASTContext &Ctx, VisibleModuleSet &VisibleModules,
                             Module *Imported, Module *CurrentModule,
                             SourceLocation ImportLoc,
                             bool IsImportingPrimaryModuleInterface = false) {
  assert(Imported->isNamedModule() &&
         "'makeTransitiveImportsVisible()' is intended for standard C++ named "
         "modules only.");
 
  llvm::SmallVector<Module *, 4> Worklist;
  Worklist.push_back(Imported);
 
  Module *FoundPrimaryModuleInterface =
      IsImportingPrimaryModuleInterface ? Imported : nullptr;
 
  while (!Worklist.empty()) {
    Module *Importing = Worklist.pop_back_val();
 
    if (VisibleModules.isVisible(Importing))
      continue;
 
    // FIXME: The ImportLoc here is not meaningful. It may be problematic if we
    // use the sourcelocation loaded from the visible modules.
    VisibleModules.setVisible(Importing, ImportLoc);
 
    if (isImportingModuleUnitFromSameModule(Ctx, Importing, CurrentModule,
                                            FoundPrimaryModuleInterface))
      for (Module *TransImported : Importing->Imports)
        if (!VisibleModules.isVisible(TransImported))
          Worklist.push_back(TransImported);
  }
}
 
Sema::DeclGroupPtrTy
Sema::ActOnGlobalModuleFragmentDecl(SourceLocation ModuleLoc) {
  // We start in the global module;
  Module *GlobalModule =
      PushGlobalModuleFragment(ModuleLoc);
 
  // All declarations created from now on are owned by the global module.
  auto *TU = Context.getTranslationUnitDecl();
  // [module.global.frag]p2
  // A global-module-fragment specifies the contents of the global module
  // fragment for a module unit. The global module fragment can be used to
  // provide declarations that are attached to the global module and usable
  // within the module unit.