Update clang to trunk r256633.

1 files changed, 506 insertions, 125 deletions

diff --git a/contrib/llvm/tools/clang/lib/Basic/VirtualFileSystem.cpp b/contrib/llvm/tools/clang/lib/Basic/VirtualFileSystem.cpp
index a36102c..cf5a8d6 100644
--- a/contrib/llvm/tools/clang/lib/Basic/VirtualFileSystem.cpp
+++ b/contrib/llvm/tools/clang/lib/Basic/VirtualFileSystem.cpp
@@ -10,6 +10,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Basic/VirtualFileSystem.h"
+#include "clang/Basic/FileManager.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
@@ -19,9 +20,17 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/YAMLParser.h"
+#include "llvm/Config/llvm-config.h"
 #include <atomic>
 #include <memory>
 
+// For chdir.
+#ifdef LLVM_ON_WIN32
+#  include <direct.h>
+#else
+#  include <unistd.h>
+#endif
+
 using namespace clang;
 using namespace clang::vfs;
 using namespace llvm;
@@ -35,12 +44,24 @@ Status::Status(const file_status &Status)
       User(Status.getUser()), Group(Status.getGroup()), Size(Status.getSize()),
       Type(Status.type()), Perms(Status.permissions()), IsVFSMapped(false)  {}
 
-Status::Status(StringRef Name, StringRef ExternalName, UniqueID UID,
-               sys::TimeValue MTime, uint32_t User, uint32_t Group,
-               uint64_t Size, file_type Type, perms Perms)
+Status::Status(StringRef Name, UniqueID UID, sys::TimeValue MTime,
+               uint32_t User, uint32_t Group, uint64_t Size, file_type Type,
+               perms Perms)
     : Name(Name), UID(UID), MTime(MTime), User(User), Group(Group), Size(Size),
       Type(Type), Perms(Perms), IsVFSMapped(false) {}
 
+Status Status::copyWithNewName(const Status &In, StringRef NewName) {
+  return Status(NewName, In.getUniqueID(), In.getLastModificationTime(),
+                In.getUser(), In.getGroup(), In.getSize(), In.getType(),
+                In.getPermissions());
+}
+
+Status Status::copyWithNewName(const file_status &In, StringRef NewName) {
+  return Status(NewName, In.getUniqueID(), In.getLastModificationTime(),
+                In.getUser(), In.getGroup(), In.getSize(), In.type(),
+                In.permissions());
+}
+
 bool Status::equivalent(const Status &Other) const {
   return getUniqueID() == Other.getUniqueID();
 }
@@ -77,6 +98,19 @@ FileSystem::getBufferForFile(const llvm::Twine &Name, int64_t FileSize,
   return (*F)->getBuffer(Name, FileSize, RequiresNullTerminator, IsVolatile);
 }
 
+std::error_code FileSystem::makeAbsolute(SmallVectorImpl<char> &Path) const {
+  auto WorkingDir = getCurrentWorkingDirectory();
+  if (!WorkingDir)
+    return WorkingDir.getError();
+
+  return llvm::sys::fs::make_absolute(WorkingDir.get(), Path);
+}
+
+bool FileSystem::exists(const Twine &Path) {
+  auto Status = status(Path);
+  return Status && Status->exists();
+}
+
 //===-----------------------------------------------------------------------===/
 // RealFileSystem implementation
 //===-----------------------------------------------------------------------===/
@@ -87,19 +121,20 @@ class RealFile : public File {
   int FD;
   Status S;
   friend class RealFileSystem;
-  RealFile(int FD) : FD(FD) {
+  RealFile(int FD, StringRef NewName)
+      : FD(FD), S(NewName, {}, {}, {}, {}, {},
+                  llvm::sys::fs::file_type::status_error, {}) {
     assert(FD >= 0 && "Invalid or inactive file descriptor");
   }
 
 public:
   ~RealFile() override;
   ErrorOr<Status> status() override;
-  ErrorOr<std::unique_ptr<MemoryBuffer>>
-  getBuffer(const Twine &Name, int64_t FileSize = -1,
-            bool RequiresNullTerminator = true,
-            bool IsVolatile = false) override;
+  ErrorOr<std::unique_ptr<MemoryBuffer>> getBuffer(const Twine &Name,
+                                                   int64_t FileSize,
+                                                   bool RequiresNullTerminator,
+                                                   bool IsVolatile) override;
   std::error_code close() override;
-  void setName(StringRef Name) override;
 };
 } // end anonymous namespace
 RealFile::~RealFile() { close(); }
@@ -110,9 +145,7 @@ ErrorOr<Status> RealFile::status() {
     file_status RealStatus;
     if (std::error_code EC = sys::fs::status(FD, RealStatus))
       return EC;
-    Status NewS(RealStatus);
-    NewS.setName(S.getName());
-    S = std::move(NewS);
+    S = Status::copyWithNewName(RealStatus, S.getName());
   }
   return S;
 }
@@ -142,10 +175,6 @@ std::error_code RealFile::close() {
   return std::error_code();
 }
 
-void RealFile::setName(StringRef Name) {
-  S.setName(Name);
-}
-
 namespace {
 /// \brief The file system according to your operating system.
 class RealFileSystem : public FileSystem {
@@ -153,6 +182,9 @@ public:
   ErrorOr<Status> status(const Twine &Path) override;
   ErrorOr<std::unique_ptr<File>> openFileForRead(const Twine &Path) override;
   directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override;
+
+  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override;
+  std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
 };
 } // end anonymous namespace
 
@@ -160,9 +192,7 @@ ErrorOr<Status> RealFileSystem::status(const Twine &Path) {
   sys::fs::file_status RealStatus;
   if (std::error_code EC = sys::fs::status(Path, RealStatus))
     return EC;
-  Status Result(RealStatus);
-  Result.setName(Path.str());
-  return Result;
+  return Status::copyWithNewName(RealStatus, Path.str());
 }
 
 ErrorOr<std::unique_ptr<File>>
@@ -170,9 +200,29 @@ RealFileSystem::openFileForRead(const Twine &Name) {
   int FD;
   if (std::error_code EC = sys::fs::openFileForRead(Name, FD))
     return EC;
-  std::unique_ptr<File> Result(new RealFile(FD));
-  Result->setName(Name.str());
-  return std::move(Result);
+  return std::unique_ptr<File>(new RealFile(FD, Name.str()));
+}
+
+llvm::ErrorOr<std::string> RealFileSystem::getCurrentWorkingDirectory() const {
+  SmallString<256> Dir;
+  if (std::error_code EC = llvm::sys::fs::current_path(Dir))
+    return EC;
+  return Dir.str().str();
+}
+
+std::error_code RealFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
+  // FIXME: chdir is thread hostile; on the other hand, creating the same
+  // behavior as chdir is complex: chdir resolves the path once, thus
+  // guaranteeing that all subsequent relative path operations work
+  // on the same path the original chdir resulted in. This makes a
+  // difference for example on network filesystems, where symlinks might be
+  // switched during runtime of the tool. Fixing this depends on having a
+  // file system abstraction that allows openat() style interactions.
+  SmallString<256> Storage;
+  StringRef Dir = Path.toNullTerminatedStringRef(Storage);
+  if (int Err = ::chdir(Dir.data()))
+    return std::error_code(Err, std::generic_category());
+  return std::error_code();
 }
 
 IntrusiveRefCntPtr<FileSystem> vfs::getRealFileSystem() {
@@ -190,10 +240,8 @@ public:
     if (!EC && Iter != llvm::sys::fs::directory_iterator()) {
       llvm::sys::fs::file_status S;
       EC = Iter->status(S);
-      if (!EC) {
-        CurrentEntry = Status(S);
-        CurrentEntry.setName(Iter->path());
-      }
+      if (!EC)
+        CurrentEntry = Status::copyWithNewName(S, Iter->path());
     }
   }
 
@@ -207,8 +255,7 @@ public:
     } else {
       llvm::sys::fs::file_status S;
       EC = Iter->status(S);
-      CurrentEntry = Status(S);
-      CurrentEntry.setName(Iter->path());
+      CurrentEntry = Status::copyWithNewName(S, Iter->path());
     }
     return EC;
   }
@@ -224,11 +271,14 @@ directory_iterator RealFileSystem::dir_begin(const Twine &Dir,
 // OverlayFileSystem implementation
 //===-----------------------------------------------------------------------===/
 OverlayFileSystem::OverlayFileSystem(IntrusiveRefCntPtr<FileSystem> BaseFS) {
-  pushOverlay(BaseFS);
+  FSList.push_back(BaseFS);
 }
 
 void OverlayFileSystem::pushOverlay(IntrusiveRefCntPtr<FileSystem> FS) {
   FSList.push_back(FS);
+  // Synchronize added file systems by duplicating the working directory from
+  // the first one in the list.
+  FS->setCurrentWorkingDirectory(getCurrentWorkingDirectory().get());
 }
 
 ErrorOr<Status> OverlayFileSystem::status(const Twine &Path) {
@@ -252,6 +302,19 @@ OverlayFileSystem::openFileForRead(const llvm::Twine &Path) {
   return make_error_code(llvm::errc::no_such_file_or_directory);
 }
 
+llvm::ErrorOr<std::string>
+OverlayFileSystem::getCurrentWorkingDirectory() const {
+  // All file systems are synchronized, just take the first working directory.
+  return FSList.front()->getCurrentWorkingDirectory();
+}
+std::error_code
+OverlayFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
+  for (auto &FS : FSList)
+    if (std::error_code EC = FS->setCurrentWorkingDirectory(Path))
+      return EC;
+  return std::error_code();
+}
+
 clang::vfs::detail::DirIterImpl::~DirIterImpl() { }
 
 namespace {
@@ -320,8 +383,286 @@ directory_iterator OverlayFileSystem::dir_begin(const Twine &Dir,
       std::make_shared<OverlayFSDirIterImpl>(Dir, *this, EC));
 }
 
+namespace clang {
+namespace vfs {
+namespace detail {
+
+enum InMemoryNodeKind { IME_File, IME_Directory };
+
+/// The in memory file system is a tree of Nodes. Every node can either be a
+/// file or a directory.
+class InMemoryNode {
+  Status Stat;
+  InMemoryNodeKind Kind;
+
+public:
+  InMemoryNode(Status Stat, InMemoryNodeKind Kind)
+      : Stat(std::move(Stat)), Kind(Kind) {}
+  virtual ~InMemoryNode() {}
+  const Status &getStatus() const { return Stat; }
+  InMemoryNodeKind getKind() const { return Kind; }
+  virtual std::string toString(unsigned Indent) const = 0;
+};
+
+namespace {
+class InMemoryFile : public InMemoryNode {
+  std::unique_ptr<llvm::MemoryBuffer> Buffer;
+
+public:
+  InMemoryFile(Status Stat, std::unique_ptr<llvm::MemoryBuffer> Buffer)
+      : InMemoryNode(std::move(Stat), IME_File), Buffer(std::move(Buffer)) {}
+
+  llvm::MemoryBuffer *getBuffer() { return Buffer.get(); }
+  std::string toString(unsigned Indent) const override {
+    return (std::string(Indent, ' ') + getStatus().getName() + "\n").str();
+  }
+  static bool classof(const InMemoryNode *N) {
+    return N->getKind() == IME_File;
+  }
+};
+
+/// Adapt a InMemoryFile for VFS' File interface.
+class InMemoryFileAdaptor : public File {
+  InMemoryFile &Node;
+
+public:
+  explicit InMemoryFileAdaptor(InMemoryFile &Node) : Node(Node) {}
+
+  llvm::ErrorOr<Status> status() override { return Node.getStatus(); }
+  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+  getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
+            bool IsVolatile) override {
+    llvm::MemoryBuffer *Buf = Node.getBuffer();
+    return llvm::MemoryBuffer::getMemBuffer(
+        Buf->getBuffer(), Buf->getBufferIdentifier(), RequiresNullTerminator);
+  }
+  std::error_code close() override { return std::error_code(); }
+};
+} // end anonymous namespace
+
+class InMemoryDirectory : public InMemoryNode {
+  std::map<std::string, std::unique_ptr<InMemoryNode>> Entries;
+
+public:
+  InMemoryDirectory(Status Stat)
+      : InMemoryNode(std::move(Stat), IME_Directory) {}
+  InMemoryNode *getChild(StringRef Name) {
+    auto I = Entries.find(Name);
+    if (I != Entries.end())
+      return I->second.get();
+    return nullptr;
+  }
+  InMemoryNode *addChild(StringRef Name, std::unique_ptr<InMemoryNode> Child) {
+    return Entries.insert(make_pair(Name, std::move(Child)))
+        .first->second.get();
+  }
+
+  typedef decltype(Entries)::const_iterator const_iterator;
+  const_iterator begin() const { return Entries.begin(); }
+  const_iterator end() const { return Entries.end(); }
+
+  std::string toString(unsigned Indent) const override {
+    std::string Result =
+        (std::string(Indent, ' ') + getStatus().getName() + "\n").str();
+    for (const auto &Entry : Entries) {
+      Result += Entry.second->toString(Indent + 2);
+    }
+    return Result;
+  }
+  static bool classof(const InMemoryNode *N) {
+    return N->getKind() == IME_Directory;
+  }
+};
+}
+
+InMemoryFileSystem::InMemoryFileSystem(bool UseNormalizedPaths)
+    : Root(new detail::InMemoryDirectory(
+          Status("", getNextVirtualUniqueID(), llvm::sys::TimeValue::MinTime(),
+                 0, 0, 0, llvm::sys::fs::file_type::directory_file,
+                 llvm::sys::fs::perms::all_all))),
+      UseNormalizedPaths(UseNormalizedPaths) {}
+
+InMemoryFileSystem::~InMemoryFileSystem() {}
+
+std::string InMemoryFileSystem::toString() const {
+  return Root->toString(/*Indent=*/0);
+}
+
+bool InMemoryFileSystem::addFile(const Twine &P, time_t ModificationTime,
+                                 std::unique_ptr<llvm::MemoryBuffer> Buffer) {
+  SmallString<128> Path;
+  P.toVector(Path);
+
+  // Fix up relative paths. This just prepends the current working directory.
+  std::error_code EC = makeAbsolute(Path);
+  assert(!EC);
+  (void)EC;
+
+  if (useNormalizedPaths())
+    llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
+
+  if (Path.empty())
+    return false;
+
+  detail::InMemoryDirectory *Dir = Root.get();
+  auto I = llvm::sys::path::begin(Path), E = llvm::sys::path::end(Path);
+  while (true) {
+    StringRef Name = *I;
+    detail::InMemoryNode *Node = Dir->getChild(Name);
+    ++I;
+    if (!Node) {
+      if (I == E) {
+        // End of the path, create a new file.
+        // FIXME: expose the status details in the interface.
+        Status Stat(P.str(), getNextVirtualUniqueID(),
+                    llvm::sys::TimeValue(ModificationTime, 0), 0, 0,
+                    Buffer->getBufferSize(),
+                    llvm::sys::fs::file_type::regular_file,
+                    llvm::sys::fs::all_all);
+        Dir->addChild(Name, llvm::make_unique<detail::InMemoryFile>(
+                                std::move(Stat), std::move(Buffer)));
+        return true;
+      }
+
+      // Create a new directory. Use the path up to here.
+      // FIXME: expose the status details in the interface.
+      Status Stat(
+          StringRef(Path.str().begin(), Name.end() - Path.str().begin()),
+          getNextVirtualUniqueID(), llvm::sys::TimeValue(ModificationTime, 0),
+          0, 0, Buffer->getBufferSize(),
+          llvm::sys::fs::file_type::directory_file, llvm::sys::fs::all_all);
+      Dir = cast<detail::InMemoryDirectory>(Dir->addChild(
+          Name, llvm::make_unique<detail::InMemoryDirectory>(std::move(Stat))));
+      continue;
+    }
+
+    if (auto *NewDir = dyn_cast<detail::InMemoryDirectory>(Node)) {
+      Dir = NewDir;
+    } else {
+      assert(isa<detail::InMemoryFile>(Node) &&
+             "Must be either file or directory!");
+
+      // Trying to insert a directory in place of a file.
+      if (I != E)
+        return false;
+
+      // Return false only if the new file is different from the existing one.
+      return cast<detail::InMemoryFile>(Node)->getBuffer()->getBuffer() ==
+             Buffer->getBuffer();
+    }
+  }
+}
+
+bool InMemoryFileSystem::addFileNoOwn(const Twine &P, time_t ModificationTime,
+                                      llvm::MemoryBuffer *Buffer) {
+  return addFile(P, ModificationTime,
+                 llvm::MemoryBuffer::getMemBuffer(
+                     Buffer->getBuffer(), Buffer->getBufferIdentifier()));
+}
+
+static ErrorOr<detail::InMemoryNode *>
+lookupInMemoryNode(const InMemoryFileSystem &FS, detail::InMemoryDirectory *Dir,
+                   const Twine &P) {
+  SmallString<128> Path;
+  P.toVector(Path);
+
+  // Fix up relative paths. This just prepends the current working directory.
+  std::error_code EC = FS.makeAbsolute(Path);
+  assert(!EC);
+  (void)EC;
+
+  if (FS.useNormalizedPaths())
+    llvm::sys::path::remove_dots(Path, /*remove_dot_dot=*/true);
+
+  if (Path.empty())
+    return Dir;
+
+  auto I = llvm::sys::path::begin(Path), E = llvm::sys::path::end(Path);
+  while (true) {
+    detail::InMemoryNode *Node = Dir->getChild(*I);
+    ++I;
+    if (!Node)
+      return errc::no_such_file_or_directory;
+
+    // Return the file if it's at the end of the path.
+    if (auto File = dyn_cast<detail::InMemoryFile>(Node)) {
+      if (I == E)
+        return File;
+      return errc::no_such_file_or_directory;
+    }
+
+    // Traverse directories.
+    Dir = cast<detail::InMemoryDirectory>(Node);
+    if (I == E)
+      return Dir;
+  }
+}
+
+llvm::ErrorOr<Status> InMemoryFileSystem::status(const Twine &Path) {
+  auto Node = lookupInMemoryNode(*this, Root.get(), Path);
+  if (Node)
+    return (*Node)->getStatus();
+  return Node.getError();
+}
+
+llvm::ErrorOr<std::unique_ptr<File>>
+InMemoryFileSystem::openFileForRead(const Twine &Path) {
+  auto Node = lookupInMemoryNode(*this, Root.get(), Path);
+  if (!Node)
+    return Node.getError();
+
+  // When we have a file provide a heap-allocated wrapper for the memory buffer
+  // to match the ownership semantics for File.
+  if (auto *F = dyn_cast<detail::InMemoryFile>(*Node))
+    return std::unique_ptr<File>(new detail::InMemoryFileAdaptor(*F));
+
+  // FIXME: errc::not_a_file?
+  return make_error_code(llvm::errc::invalid_argument);
+}
+
+namespace {
+/// Adaptor from InMemoryDir::iterator to directory_iterator.
+class InMemoryDirIterator : public clang::vfs::detail::DirIterImpl {
+  detail::InMemoryDirectory::const_iterator I;
+  detail::InMemoryDirectory::const_iterator E;
+
+public:
+  InMemoryDirIterator() {}
+  explicit InMemoryDirIterator(detail::InMemoryDirectory &Dir)
+      : I(Dir.begin()), E(Dir.end()) {
+    if (I != E)
+      CurrentEntry = I->second->getStatus();
+  }
+
+  std::error_code increment() override {
+    ++I;
+    // When we're at the end, make CurrentEntry invalid and DirIterImpl will do
+    // the rest.
+    CurrentEntry = I != E ? I->second->getStatus() : Status();
+    return std::error_code();
+  }
+};
+} // end anonymous namespace
+
+directory_iterator InMemoryFileSystem::dir_begin(const Twine &Dir,
+                                                 std::error_code &EC) {
+  auto Node = lookupInMemoryNode(*this, Root.get(), Dir);
+  if (!Node) {
+    EC = Node.getError();
+    return directory_iterator(std::make_shared<InMemoryDirIterator>());
+  }
+
+  if (auto *DirNode = dyn_cast<detail::InMemoryDirectory>(*Node))
+    return directory_iterator(std::make_shared<InMemoryDirIterator>(*DirNode));
+
+  EC = make_error_code(llvm::errc::not_a_directory);
+  return directory_iterator(std::make_shared<InMemoryDirIterator>());
+}
+}
+}
+
 //===-----------------------------------------------------------------------===/
-// VFSFromYAML implementation
+// RedirectingFileSystem implementation
 //===-----------------------------------------------------------------------===/
 
 namespace {
@@ -343,23 +684,24 @@ public:
   EntryKind getKind() const { return Kind; }
 };
 
-class DirectoryEntry : public Entry {
-  std::vector<Entry *> Contents;
+class RedirectingDirectoryEntry : public Entry {
+  std::vector<std::unique_ptr<Entry>> Contents;
   Status S;
 
 public:
-  ~DirectoryEntry() override;
-  DirectoryEntry(StringRef Name, std::vector<Entry *> Contents, Status S)
+  RedirectingDirectoryEntry(StringRef Name,
+                            std::vector<std::unique_ptr<Entry>> Contents,
+                            Status S)
       : Entry(EK_Directory, Name), Contents(std::move(Contents)),
         S(std::move(S)) {}
   Status getStatus() { return S; }
-  typedef std::vector<Entry *>::iterator iterator;
+  typedef decltype(Contents)::iterator iterator;
   iterator contents_begin() { return Contents.begin(); }
   iterator contents_end() { return Contents.end(); }
   static bool classof(const Entry *E) { return E->getKind() == EK_Directory; }
 };
 
-class FileEntry : public Entry {
+class RedirectingFileEntry : public Entry {
 public:
   enum NameKind {
     NK_NotSet,
@@ -370,7 +712,8 @@ private:
   std::string ExternalContentsPath;
   NameKind UseName;
 public:
-  FileEntry(StringRef Name, StringRef ExternalContentsPath, NameKind UseName)
+  RedirectingFileEntry(StringRef Name, StringRef ExternalContentsPath,
+                       NameKind UseName)
       : Entry(EK_File, Name), ExternalContentsPath(ExternalContentsPath),
         UseName(UseName) {}
   StringRef getExternalContentsPath() const { return ExternalContentsPath; }
@@ -382,16 +725,18 @@ public:
   static bool classof(const Entry *E) { return E->getKind() == EK_File; }
 };
 
-class VFSFromYAML;
+class RedirectingFileSystem;
 
 class VFSFromYamlDirIterImpl : public clang::vfs::detail::DirIterImpl {
   std::string Dir;
-  VFSFromYAML &FS;
-  DirectoryEntry::iterator Current, End;
+  RedirectingFileSystem &FS;
+  RedirectingDirectoryEntry::iterator Current, End;
+
 public:
-  VFSFromYamlDirIterImpl(const Twine &Path, VFSFromYAML &FS,
-                         DirectoryEntry::iterator Begin,
-                         DirectoryEntry::iterator End, std::error_code &EC);
+  VFSFromYamlDirIterImpl(const Twine &Path, RedirectingFileSystem &FS,
+                         RedirectingDirectoryEntry::iterator Begin,
+                         RedirectingDirectoryEntry::iterator End,
+                         std::error_code &EC);
   std::error_code increment() override;
 };
 
@@ -448,8 +793,9 @@ public:
 /// In both cases, the 'name' field may contain multiple path components (e.g.
 /// /path/to/file). However, any directory that contains more than one child
 /// must be uniquely represented by a directory entry.
-class VFSFromYAML : public vfs::FileSystem {
-  std::vector<Entry *> Roots; ///< The root(s) of the virtual file system.
+class RedirectingFileSystem : public vfs::FileSystem {
+  /// The root(s) of the virtual file system.
+  std::vector<std::unique_ptr<Entry>> Roots;
   /// \brief The file system to use for external references.
   IntrusiveRefCntPtr<FileSystem> ExternalFS;
 
@@ -466,10 +812,10 @@ class VFSFromYAML : public vfs::FileSystem {
   bool UseExternalNames;
   /// @}
 
-  friend class VFSFromYAMLParser;
+  friend class RedirectingFileSystemParser;
 
 private:
-  VFSFromYAML(IntrusiveRefCntPtr<FileSystem> ExternalFS)
+  RedirectingFileSystem(IntrusiveRefCntPtr<FileSystem> ExternalFS)
       : ExternalFS(ExternalFS), CaseSensitive(true), UseExternalNames(true) {}
 
   /// \brief Looks up \p Path in \c Roots.
@@ -484,18 +830,23 @@ private:
   ErrorOr<Status> status(const Twine &Path, Entry *E);
 
 public:
-  ~VFSFromYAML() override;
-
   /// \brief Parses \p Buffer, which is expected to be in YAML format and
   /// returns a virtual file system representing its contents.
-  static VFSFromYAML *create(std::unique_ptr<MemoryBuffer> Buffer,
-                             SourceMgr::DiagHandlerTy DiagHandler,
-                             void *DiagContext,
-                             IntrusiveRefCntPtr<FileSystem> ExternalFS);
+  static RedirectingFileSystem *
+  create(std::unique_ptr<MemoryBuffer> Buffer,
+         SourceMgr::DiagHandlerTy DiagHandler, void *DiagContext,
+         IntrusiveRefCntPtr<FileSystem> ExternalFS);
 
   ErrorOr<Status> status(const Twine &Path) override;
   ErrorOr<std::unique_ptr<File>> openFileForRead(const Twine &Path) override;
 
+  llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override {
+    return ExternalFS->getCurrentWorkingDirectory();
+  }
+  std::error_code setCurrentWorkingDirectory(const Twine &Path) override {
+    return ExternalFS->setCurrentWorkingDirectory(Path);
+  }
+
   directory_iterator dir_begin(const Twine &Dir, std::error_code &EC) override{
     ErrorOr<Entry *> E = lookupPath(Dir);
     if (!E) {
@@ -513,14 +864,14 @@ public:
       return directory_iterator();
     }
 
-    DirectoryEntry *D = cast<DirectoryEntry>(*E);
+    auto *D = cast<RedirectingDirectoryEntry>(*E);
     return directory_iterator(std::make_shared<VFSFromYamlDirIterImpl>(Dir,
         *this, D->contents_begin(), D->contents_end(), EC));
   }
 };
 
 /// \brief A helper class to hold the common YAML parsing state.
-class VFSFromYAMLParser {
+class RedirectingFileSystemParser {
   yaml::Stream &Stream;
 
   void error(yaml::Node *N, const Twine &Msg) {
@@ -596,7 +947,7 @@ class VFSFromYAMLParser {
     return true;
   }
 
-  Entry *parseEntry(yaml::Node *N) {
+  std::unique_ptr<Entry> parseEntry(yaml::Node *N) {
     yaml::MappingNode *M = dyn_cast<yaml::MappingNode>(N);
     if (!M) {
       error(N, "expected mapping node for file or directory entry");
@@ -611,14 +962,13 @@ class VFSFromYAMLParser {
       KeyStatusPair("use-external-name", false),
     };
 
-    DenseMap<StringRef, KeyStatus> Keys(
-        &Fields[0], Fields + sizeof(Fields)/sizeof(Fields[0]));
+    DenseMap<StringRef, KeyStatus> Keys(std::begin(Fields), std::end(Fields));
 
     bool HasContents = false; // external or otherwise
-    std::vector<Entry *> EntryArrayContents;
+    std::vector<std::unique_ptr<Entry>> EntryArrayContents;
     std::string ExternalContentsPath;
     std::string Name;
-    FileEntry::NameKind UseExternalName = FileEntry::NK_NotSet;
+    auto UseExternalName = RedirectingFileEntry::NK_NotSet;
     EntryKind Kind;
 
     for (yaml::MappingNode::iterator I = M->begin(), E = M->end(); I != E;
@@ -667,8 +1017,8 @@ class VFSFromYAMLParser {
         for (yaml::SequenceNode::iterator I = Contents->begin(),
                                           E = Contents->end();
              I != E; ++I) {
-          if (Entry *E = parseEntry(&*I))
-            EntryArrayContents.push_back(E);
+          if (std::unique_ptr<Entry> E = parseEntry(&*I))
+            EntryArrayContents.push_back(std::move(E));
           else
             return nullptr;
         }
@@ -686,7 +1036,8 @@ class VFSFromYAMLParser {
         bool Val;
         if (!parseScalarBool(I->getValue(), Val))
           return nullptr;
-        UseExternalName = Val ? FileEntry::NK_External : FileEntry::NK_Virtual;
+        UseExternalName = Val ? RedirectingFileEntry::NK_External
+                              : RedirectingFileEntry::NK_Virtual;
       } else {
         llvm_unreachable("key missing from Keys");
       }
@@ -704,7 +1055,8 @@ class VFSFromYAMLParser {
       return nullptr;
 
     // check invalid configuration
-    if (Kind == EK_Directory && UseExternalName != FileEntry::NK_NotSet) {
+    if (Kind == EK_Directory &&
+        UseExternalName != RedirectingFileEntry::NK_NotSet) {
       error(N, "'use-external-name' is not supported for directories");
       return nullptr;
     }
@@ -718,16 +1070,17 @@ class VFSFromYAMLParser {
     // Get the last component
     StringRef LastComponent = sys::path::filename(Trimmed);
 
-    Entry *Result = nullptr;
+    std::unique_ptr<Entry> Result;
     switch (Kind) {
     case EK_File:
-      Result = new FileEntry(LastComponent, std::move(ExternalContentsPath),
-                             UseExternalName);
+      Result = llvm::make_unique<RedirectingFileEntry>(
+          LastComponent, std::move(ExternalContentsPath), UseExternalName);
       break;
     case EK_Directory:
-      Result = new DirectoryEntry(LastComponent, std::move(EntryArrayContents),
-          Status("", "", getNextVirtualUniqueID(), sys::TimeValue::now(), 0, 0,
-                 0, file_type::directory_file, sys::fs::all_all));
+      Result = llvm::make_unique<RedirectingDirectoryEntry>(
+          LastComponent, std::move(EntryArrayContents),
+          Status("", getNextVirtualUniqueID(), sys::TimeValue::now(), 0, 0, 0,
+                 file_type::directory_file, sys::fs::all_all));
       break;
     }
 
@@ -739,18 +1092,21 @@ class VFSFromYAMLParser {
     for (sys::path::reverse_iterator I = sys::path::rbegin(Parent),
                                      E = sys::path::rend(Parent);
          I != E; ++I) {
-      Result = new DirectoryEntry(*I, llvm::makeArrayRef(Result),
-          Status("", "", getNextVirtualUniqueID(), sys::TimeValue::now(), 0, 0,
-                 0, file_type::directory_file, sys::fs::all_all));
+      std::vector<std::unique_ptr<Entry>> Entries;
+      Entries.push_back(std::move(Result));
+      Result = llvm::make_unique<RedirectingDirectoryEntry>(
+          *I, std::move(Entries),
+          Status("", getNextVirtualUniqueID(), sys::TimeValue::now(), 0, 0, 0,
+                 file_type::directory_file, sys::fs::all_all));
     }
     return Result;
   }
 
 public:
-  VFSFromYAMLParser(yaml::Stream &S) : Stream(S) {}
+  RedirectingFileSystemParser(yaml::Stream &S) : Stream(S) {}
 
   // false on error
-  bool parse(yaml::Node *Root, VFSFromYAML *FS) {
+  bool parse(yaml::Node *Root, RedirectingFileSystem *FS) {
     yaml::MappingNode *Top = dyn_cast<yaml::MappingNode>(Root);
     if (!Top) {
       error(Root, "expected mapping node");
@@ -764,8 +1120,7 @@ public:
       KeyStatusPair("roots", true),
     };
 
-    DenseMap<StringRef, KeyStatus> Keys(
-        &Fields[0], Fields + sizeof(Fields)/sizeof(Fields[0]));
+    DenseMap<StringRef, KeyStatus> Keys(std::begin(Fields), std::end(Fields));
 
     // Parse configuration and 'roots'
     for (yaml::MappingNode::iterator I = Top->begin(), E = Top->end(); I != E;
@@ -787,8 +1142,8 @@ public:
 
         for (yaml::SequenceNode::iterator I = Roots->begin(), E = Roots->end();
              I != E; ++I) {
-          if (Entry *E = parseEntry(&*I))
-            FS->Roots.push_back(E);
+          if (std::unique_ptr<Entry> E = parseEntry(&*I))
+            FS->Roots.push_back(std::move(E));
           else
             return false;
         }
@@ -831,15 +1186,11 @@ public:
 };
 } // end of anonymous namespace
 
-Entry::~Entry() {}
-DirectoryEntry::~DirectoryEntry() { llvm::DeleteContainerPointers(Contents); }
+Entry::~Entry() = default;
 
-VFSFromYAML::~VFSFromYAML() { llvm::DeleteContainerPointers(Roots); }
-
-VFSFromYAML *VFSFromYAML::create(std::unique_ptr<MemoryBuffer> Buffer,
-                                 SourceMgr::DiagHandlerTy DiagHandler,
-                                 void *DiagContext,
-                                 IntrusiveRefCntPtr<FileSystem> ExternalFS) {
+RedirectingFileSystem *RedirectingFileSystem::create(
+    std::unique_ptr<MemoryBuffer> Buffer, SourceMgr::DiagHandlerTy DiagHandler,
+    void *DiagContext, IntrusiveRefCntPtr<FileSystem> ExternalFS) {
 
   SourceMgr SM;
   yaml::Stream Stream(Buffer->getMemBufferRef(), SM);
@@ -852,21 +1203,22 @@ VFSFromYAML *VFSFromYAML::create(std::unique_ptr<MemoryBuffer> Buffer,
     return nullptr;
   }
 
-  VFSFromYAMLParser P(Stream);
+  RedirectingFileSystemParser P(Stream);
 
-  std::unique_ptr<VFSFromYAML> FS(new VFSFromYAML(ExternalFS));
+  std::unique_ptr<RedirectingFileSystem> FS(
+      new RedirectingFileSystem(ExternalFS));
   if (!P.parse(Root, FS.get()))
     return nullptr;
 
   return FS.release();
 }
 
-ErrorOr<Entry *> VFSFromYAML::lookupPath(const Twine &Path_) {
+ErrorOr<Entry *> RedirectingFileSystem::lookupPath(const Twine &Path_) {
   SmallString<256> Path;
   Path_.toVector(Path);
 
   // Handle relative paths
-  if (std::error_code EC = sys::fs::make_absolute(Path))
+  if (std::error_code EC = makeAbsolute(Path))
     return EC;
 
   if (Path.empty())
@@ -874,18 +1226,17 @@ ErrorOr<Entry *> VFSFromYAML::lookupPath(const Twine &Path_) {
 
   sys::path::const_iterator Start = sys::path::begin(Path);
   sys::path::const_iterator End = sys::path::end(Path);
-  for (std::vector<Entry *>::iterator I = Roots.begin(), E = Roots.end();
-       I != E; ++I) {
-    ErrorOr<Entry *> Result = lookupPath(Start, End, *I);
+  for (const std::unique_ptr<Entry> &Root : Roots) {
+    ErrorOr<Entry *> Result = lookupPath(Start, End, Root.get());
     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
       return Result;
   }
   return make_error_code(llvm::errc::no_such_file_or_directory);
 }
 
-ErrorOr<Entry *> VFSFromYAML::lookupPath(sys::path::const_iterator Start,
-                                         sys::path::const_iterator End,
-                                         Entry *From) {
+ErrorOr<Entry *>
+RedirectingFileSystem::lookupPath(sys::path::const_iterator Start,
+                                  sys::path::const_iterator End, Entry *From) {
   if (Start->equals("."))
     ++Start;
 
@@ -902,52 +1253,78 @@ ErrorOr<Entry *> VFSFromYAML::lookupPath(sys::path::const_iterator Start,
     return From;
   }
 
-  DirectoryEntry *DE = dyn_cast<DirectoryEntry>(From);
+  auto *DE = dyn_cast<RedirectingDirectoryEntry>(From);
   if (!DE)
     return make_error_code(llvm::errc::not_a_directory);
 
-  for (DirectoryEntry::iterator I = DE->contents_begin(),
-                                E = DE->contents_end();
-       I != E; ++I) {
-    ErrorOr<Entry *> Result = lookupPath(Start, End, *I);
+  for (const std::unique_ptr<Entry> &DirEntry :
+       llvm::make_range(DE->contents_begin(), DE->contents_end())) {
+    ErrorOr<Entry *> Result = lookupPath(Start, End, DirEntry.get());
     if (Result || Result.getError() != llvm::errc::no_such_file_or_directory)
       return Result;
   }
   return make_error_code(llvm::errc::no_such_file_or_directory);
 }
 
-ErrorOr<Status> VFSFromYAML::status(const Twine &Path, Entry *E) {
+static Status getRedirectedFileStatus(const Twine &Path, bool UseExternalNames,
+                                      Status ExternalStatus) {
+  Status S = ExternalStatus;
+  if (!UseExternalNames)
+    S = Status::copyWithNewName(S, Path.str());
+  S.IsVFSMapped = true;
+  return S;
+}
+
+ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path, Entry *E) {
   assert(E != nullptr);
-  std::string PathStr(Path.str());
-  if (FileEntry *F = dyn_cast<FileEntry>(E)) {
+  if (auto *F = dyn_cast<RedirectingFileEntry>(E)) {
     ErrorOr<Status> S = ExternalFS->status(F->getExternalContentsPath());
     assert(!S || S->getName() == F->getExternalContentsPath());
-    if (S && !F->useExternalName(UseExternalNames))
-      S->setName(PathStr);
     if (S)
-      S->IsVFSMapped = true;
+      return getRedirectedFileStatus(Path, F->useExternalName(UseExternalNames),
+                                     *S);
     return S;
   } else { // directory
-    DirectoryEntry *DE = cast<DirectoryEntry>(E);
-    Status S = DE->getStatus();
-    S.setName(PathStr);
-    return S;
+    auto *DE = cast<RedirectingDirectoryEntry>(E);
+    return Status::copyWithNewName(DE->getStatus(), Path.str());
   }
 }
 
-ErrorOr<Status> VFSFromYAML::status(const Twine &Path) {
+ErrorOr<Status> RedirectingFileSystem::status(const Twine &Path) {
   ErrorOr<Entry *> Result = lookupPath(Path);
   if (!Result)
     return Result.getError();
   return status(Path, *Result);
 }
 
-ErrorOr<std::unique_ptr<File>> VFSFromYAML::openFileForRead(const Twine &Path) {
+namespace {
+/// Provide a file wrapper with an overriden status.
+class FileWithFixedStatus : public File {
+  std::unique_ptr<File> InnerFile;
+  Status S;
+
+public:
+  FileWithFixedStatus(std::unique_ptr<File> InnerFile, Status S)
+      : InnerFile(std::move(InnerFile)), S(S) {}
+
+  ErrorOr<Status> status() override { return S; }
+  ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
+  getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
+            bool IsVolatile) override {
+    return InnerFile->getBuffer(Name, FileSize, RequiresNullTerminator,
+                                IsVolatile);
+  }
+  std::error_code close() override { return InnerFile->close(); }
+};
+} // end anonymous namespace
+
+ErrorOr<std::unique_ptr<File>>
+RedirectingFileSystem::openFileForRead(const Twine &Path) {
   ErrorOr<Entry *> E = lookupPath(Path);
   if (!E)
     return E.getError();
 
-  FileEntry *F = dyn_cast<FileEntry>(*E);
+  auto *F = dyn_cast<RedirectingFileEntry>(*E);
   if (!F) // FIXME: errc::not_a_file?
     return make_error_code(llvm::errc::invalid_argument);
 
@@ -955,18 +1332,23 @@ ErrorOr<std::unique_ptr<File>> VFSFromYAML::openFileForRead(const Twine &Path) {
   if (!Result)
     return Result;
 
-  if (!F->useExternalName(UseExternalNames))
-    (*Result)->setName(Path.str());
+  auto ExternalStatus = (*Result)->status();
+  if (!ExternalStatus)
+    return ExternalStatus.getError();
 
-  return Result;
+  // FIXME: Update the status with the name and VFSMapped.
+  Status S = getRedirectedFileStatus(Path, F->useExternalName(UseExternalNames),
+                                     *ExternalStatus);
+  return std::unique_ptr<File>(
+      llvm::make_unique<FileWithFixedStatus>(std::move(*Result), S));
 }
 
 IntrusiveRefCntPtr<FileSystem>
 vfs::getVFSFromYAML(std::unique_ptr<MemoryBuffer> Buffer,
                     SourceMgr::DiagHandlerTy DiagHandler, void *DiagContext,
                     IntrusiveRefCntPtr<FileSystem> ExternalFS) {
-  return VFSFromYAML::create(std::move(Buffer), DiagHandler, DiagContext,
-                             ExternalFS);
+  return RedirectingFileSystem::create(std::move(Buffer), DiagHandler,
+                                       DiagContext, ExternalFS);
 }
 
 UniqueID vfs::getNextVirtualUniqueID() {
@@ -1111,11 +1493,10 @@ void YAMLVFSWriter::write(llvm::raw_ostream &OS) {
   JSONWriter(OS).write(Mappings, IsCaseSensitive);
 }
 
-VFSFromYamlDirIterImpl::VFSFromYamlDirIterImpl(const Twine &_Path,
-                                               VFSFromYAML &FS,
-                                               DirectoryEntry::iterator Begin,
-                                               DirectoryEntry::iterator End,
-                                               std::error_code &EC)
+VFSFromYamlDirIterImpl::VFSFromYamlDirIterImpl(
+    const Twine &_Path, RedirectingFileSystem &FS,
+    RedirectingDirectoryEntry::iterator Begin,
+    RedirectingDirectoryEntry::iterator End, std::error_code &EC)
     : Dir(_Path.str()), FS(FS), Current(Begin), End(End) {
   if (Current != End) {
     SmallString<128> PathStr(Dir);