Index: lib/Basic/FileManager.cpp
===================================================================
--- lib/Basic/FileManager.cpp
+++ lib/Basic/FileManager.cpp
@@ -511,6 +511,12 @@
   UniqueRealFiles.erase(Entry->getUniqueID());
 }
 
+// For GNU Hurd
+#if defined(__GNU__) && !defined(PATH_MAX)
+# define PATH_MAX 4096
+#endif
+
+
 void FileManager::GetUniqueIDMapping(
                    SmallVectorImpl<const FileEntry *> &UIDToFiles) const {
   UIDToFiles.clear();
Index: lib/Frontend/ModuleDependencyCollector.cpp
===================================================================
--- lib/Frontend/ModuleDependencyCollector.cpp
+++ lib/Frontend/ModuleDependencyCollector.cpp
@@ -99,6 +99,11 @@
 
 }
 
+// For GNU Hurd
+#if defined(__GNU__) && !defined(PATH_MAX)
+# define PATH_MAX 4096
+#endif
+
 // TODO: move this to Support/Path.h and check for HAVE_REALPATH?
 static bool real_path(StringRef SrcPath, SmallVectorImpl<char> &RealPath) {
 #ifdef LLVM_ON_UNIX