From b857398ff9c31660c652db755dabfb708254105e Mon Sep 17 00:00:00 2001
From: Eric Liu <ioeric@google.com>
Date: Thu, 17 May 2018 10:26:23 +0000
Subject: [PATCH] Add vfs::FileSystem::getRealPath

Summary: And change `FileManager::getCanonicalName` to use getRealPath.

Reviewers: bkramer

Reviewed By: bkramer

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D46942

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@332590 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/VirtualFileSystem.h |  6 ++++++
 lib/Basic/FileManager.cpp               | 18 ++----------------
 lib/Basic/VirtualFileSystem.cpp         | 13 +++++++++++++
 3 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/include/clang/Basic/VirtualFileSystem.h b/include/clang/Basic/VirtualFileSystem.h
index 813e746df2..59e33791f2 100644
--- a/include/clang/Basic/VirtualFileSystem.h
+++ b/include/clang/Basic/VirtualFileSystem.h
@@ -248,6 +248,12 @@ public:
   /// Get the working directory of this file system.
   virtual llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const = 0;
 
+  /// Gets real path of \p Path e.g. collapse all . and .. patterns, resolve
+  /// symlinks. For real file system, this uses `llvm::sys::fs::real_path`.
+  /// This returns errc::operation_not_permitted if not implemented by subclass.
+  virtual std::error_code getRealPath(const Twine &Path,
+                                      SmallVectorImpl<char> &Output) const;
+
   /// Check whether a file exists. Provided for convenience.
   bool exists(const Twine &Path);
 
diff --git a/lib/Basic/FileManager.cpp b/lib/Basic/FileManager.cpp
index 14a9033b20..5cbcdf4477 100644
--- a/lib/Basic/FileManager.cpp
+++ b/lib/Basic/FileManager.cpp
@@ -534,23 +534,9 @@ StringRef FileManager::getCanonicalName(const DirectoryEntry *Dir) {
 
   StringRef CanonicalName(Dir->getName());
 
-#ifdef LLVM_ON_UNIX
-  char CanonicalNameBuf[PATH_MAX];
-  if (realpath(Dir->getName().str().c_str(), CanonicalNameBuf))
+  SmallString<4096> CanonicalNameBuf;
+  if (!FS->getRealPath(Dir->getName(), CanonicalNameBuf))
     CanonicalName = StringRef(CanonicalNameBuf).copy(CanonicalNameStorage);
-#else
-  SmallString<256> CanonicalNameBuf(CanonicalName);
-  llvm::sys::fs::make_absolute(CanonicalNameBuf);
-  llvm::sys::path::native(CanonicalNameBuf);
-  // We've run into needing to remove '..' here in the wild though, so
-  // remove it.
-  // On Windows, symlinks are significantly less prevalent, so removing
-  // '..' is pretty safe.
-  // Ideally we'd have an equivalent of `realpath` and could implement
-  // sys::fs::canonical across all the platforms.
-  llvm::sys::path::remove_dots(CanonicalNameBuf, /* remove_dot_dot */ true);
-  CanonicalName = StringRef(CanonicalNameBuf).copy(CanonicalNameStorage);
-#endif
 
   CanonicalDirNames.insert(std::make_pair(Dir, CanonicalName));
   return CanonicalName;
diff --git a/lib/Basic/VirtualFileSystem.cpp b/lib/Basic/VirtualFileSystem.cpp
index 84684a4165..1727b7d0e7 100644
--- a/lib/Basic/VirtualFileSystem.cpp
+++ b/lib/Basic/VirtualFileSystem.cpp
@@ -139,6 +139,11 @@ std::error_code FileSystem::makeAbsolute(SmallVectorImpl<char> &Path) const {
   return llvm::sys::fs::make_absolute(WorkingDir.get(), Path);
 }
 
+std::error_code FileSystem::getRealPath(const Twine &Path,
+                                        SmallVectorImpl<char> &Output) const {
+  return errc::operation_not_permitted;
+}
+
 bool FileSystem::exists(const Twine &Path) {
   auto Status = status(Path);
   return Status && Status->exists();
@@ -236,6 +241,8 @@ public:
 
   llvm::ErrorOr<std::string> getCurrentWorkingDirectory() const override;
   std::error_code setCurrentWorkingDirectory(const Twine &Path) override;
+  std::error_code getRealPath(const Twine &Path,
+                              SmallVectorImpl<char> &Output) const override;
 };
 
 } // namespace
@@ -274,6 +281,12 @@ std::error_code RealFileSystem::setCurrentWorkingDirectory(const Twine &Path) {
   return llvm::sys::fs::set_current_path(Path);
 }
 
+std::error_code
+RealFileSystem::getRealPath(const Twine &Path,
+                            SmallVectorImpl<char> &Output) const {
+  return llvm::sys::fs::real_path(Path, Output);
+}
+
 IntrusiveRefCntPtr<FileSystem> vfs::getRealFileSystem() {
   static IntrusiveRefCntPtr<FileSystem> FS = new RealFileSystem();
   return FS;
-- 
2.40.0