1 files changed, 73 insertions, 30 deletions

diff --git a/llvm/lib/Support/VirtualFileSystem.cpp b/llvm/lib/Support/VirtualFileSystem.cpp
index afa02752031..1f5c622cfaa 100644
--- a/llvm/lib/Support/VirtualFileSystem.cpp
+++ b/llvm/lib/Support/VirtualFileSystem.cpp
@@ -228,9 +228,28 @@ std::error_code RealFile::close() {
 
 namespace {
 
-/// The file system according to your operating system.
+/// A file system according to your operating system.
+/// This may be linked to the process's working directory, or maintain its own.
+///
+/// Currently, its own working directory is emulated by storing the path and
+/// sending absolute paths to llvm::sys::fs:: functions.
+/// A more principled approach would be to push this down a level, modelling
+/// the working dir as an llvm::sys::fs::WorkingDir or similar.
+/// This would enable the use of openat()-style functions on some platforms.
 class RealFileSystem : public FileSystem {
 public:
+  explicit RealFileSystem(bool LinkCWDToProcess) {
+    if (!LinkCWDToProcess) {
+      SmallString<128> PWD, RealPWD;
+      if (llvm::sys::fs::current_path(PWD))
+        return; // Awful, but nothing to do here.
+      if (llvm::sys::fs::real_path(PWD, RealPWD))
+        WD = {PWD, PWD};
+      else
+        WD = {PWD, RealPWD};
+    }
+  }
+
   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;
@@ -242,15 +261,32 @@ public:
                               SmallVectorImpl<char> &Output) const override;
 
 private:
-  mutable std::mutex CWDMutex;
-  mutable std::string CWDCache;
+  // If this FS has its own working dir, use it to make Path absolute.
+  // The returned twine is safe to use as long as both Storage and Path live.
+  Twine adjustPath(const Twine &Path, SmallVectorImpl<char> &Storage) const {
+    if (!WD)
+      return Path;
+    Path.toVector(Storage);
+    sys::fs::make_absolute(WD->Resolved, Storage);
+    return Storage;
+  }
+
+  struct WorkingDirectory {
+    // The current working directory, without symlinks resolved. (echo $PWD).
+    SmallString<128> Specified;
+    // The current working directory, with links resolved. (readlink .).
+    SmallString<128> Resolved;
+  };
+  Optional<WorkingDirectory> WD;
 };
 
 } // namespace
 
 ErrorOr<Status> RealFileSystem::status(const Twine &Path) {
+  SmallString<256> Storage;
   sys::fs::file_status RealStatus;
-  if (std::error_code EC = sys::fs::status(Path, RealStatus))
+  if (std::error_code EC =
+          sys::fs::status(adjustPath(Path, Storage), RealStatus))
     return EC;
   return Status::copyWithNewName(RealStatus, Path.str());
 }
@@ -258,56 +294,61 @@ ErrorOr<Status> RealFileSystem::status(const Twine &Path) {
 ErrorOr<std::unique_ptr<File>>
 RealFileSystem::openFileForRead(const Twine &Name) {
   int FD;
-  SmallString<256> RealName;
-  if (std::error_code EC =
-          sys::fs::openFileForRead(Name, FD, sys::fs::OF_None, &RealName))
+  SmallString<256> RealName, Storage;
+  if (std::error_code EC = sys::fs::openFileForRead(
+          adjustPath(Name, Storage), FD, sys::fs::OF_None, &RealName))
     return EC;
   return std::unique_ptr<File>(new RealFile(FD, Name.str(), RealName.str()));
 }
 
 llvm::ErrorOr<std::string> RealFileSystem::getCurrentWorkingDirectory() const {
-  std::lock_guard<std::mutex> Lock(CWDMutex);
-  if (!CWDCache.empty())
-    return CWDCache;
-  SmallString<256> Dir;
+  if (WD)
+    return WD->Specified.str();
+
+  SmallString<128> Dir;
   if (std::error_code EC = llvm::sys::fs::current_path(Dir))
     return EC;
-  CWDCache = Dir.str();
-  return CWDCache;
+  return Dir.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.
-  if (auto EC = llvm::sys::fs::set_current_path(Path))
-    return EC;
-
-  // Invalidate cache.
-  std::lock_guard<std::mutex> Lock(CWDMutex);
-  CWDCache.clear();
+  if (!WD)
+    return llvm::sys::fs::set_current_path(Path);
+
+  SmallString<128> Absolute, Resolved, Storage;
+  adjustPath(Path, Storage).toVector(Absolute);
+  bool IsDir;
+  if (auto Err = llvm::sys::fs::is_directory(Absolute, IsDir))
+    return Err;
+  if (!IsDir)
+    return std::make_error_code(std::errc::not_a_directory);
+  if (auto Err = llvm::sys::fs::real_path(Absolute, Resolved))
+    return Err;
+  WD = {Absolute, Resolved};
   return std::error_code();
 }
 
 std::error_code RealFileSystem::isLocal(const Twine &Path, bool &Result) {
-  return llvm::sys::fs::is_local(Path, Result);
+  SmallString<256> Storage;
+  return llvm::sys::fs::is_local(adjustPath(Path, Storage), Result);
 }
 
 std::error_code
 RealFileSystem::getRealPath(const Twine &Path,
                             SmallVectorImpl<char> &Output) const {
-  return llvm::sys::fs::real_path(Path, Output);
+  SmallString<256> Storage;
+  return llvm::sys::fs::real_path(adjustPath(Path, Storage), Output);
 }
 
 IntrusiveRefCntPtr<FileSystem> vfs::getRealFileSystem() {
-  static IntrusiveRefCntPtr<FileSystem> FS = new RealFileSystem();
+  static IntrusiveRefCntPtr<FileSystem> FS(new RealFileSystem(true));
   return FS;
 }
 
+std::unique_ptr<FileSystem> vfs::createPhysicalFileSystem() {
+  return llvm::make_unique<RealFileSystem>(false);
+}
+
 namespace {
 
 class RealFSDirIter : public llvm::vfs::detail::DirIterImpl {
@@ -333,7 +374,9 @@ public:
 
 directory_iterator RealFileSystem::dir_begin(const Twine &Dir,
                                              std::error_code &EC) {
-  return directory_iterator(std::make_shared<RealFSDirIter>(Dir, EC));
+  SmallString<128> Storage;
+  return directory_iterator(
+      std::make_shared<RealFSDirIter>(adjustPath(Dir, Storage), EC));
 }
 
 //===-----------------------------------------------------------------------===/