1 files changed, 16 insertions, 2 deletions
diff --git a/clang/lib/Basic/FileManager.cpp b/clang/lib/Basic/FileManager.cpp
index 6fc00d9f413..719b2f66515 100644
--- a/clang/lib/Basic/FileManager.cpp
+++ b/clang/lib/Basic/FileManager.cpp
@@ -534,9 +534,23 @@ StringRef FileManager::getCanonicalName(const DirectoryEntry *Dir) {
 
   StringRef CanonicalName(Dir->getName());
 
-  SmallString<256> CanonicalNameBuf;
-  if (!llvm::sys::fs::real_path(Dir->getName(), CanonicalNameBuf))
+#ifdef LLVM_ON_UNIX
+  char CanonicalNameBuf[PATH_MAX];
+  if (realpath(Dir->getName().str().c_str(), 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;