Index: lib/Fuzzer/FuzzerIOWindows.cpp
===================================================================
--- lib/Fuzzer/FuzzerIOWindows.cpp
+++ lib/Fuzzer/FuzzerIOWindows.cpp
@@ -21,6 +21,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <windows.h>
+#include <Shlwapi.h>
 
 namespace fuzzer {
 
@@ -140,7 +141,10 @@
 }
 
 std::string DirName(const std::string &FileName) {
-  assert(0 && "Unimplemented");
+  std::string Res = FileName;
+  PathRemoveFileSpecA(&Res[0]);
+  Res.resize(std::strlen(Res.c_str()));
+  return Res;
 }
 
 }  // namespace fuzzer