diff -r 5d306df084eb -r 0f2fe7d37d8c src/os/windows/vm/os_windows.cpp
--- a/src/os/windows/vm/os_windows.cpp	Tue Apr 30 14:49:19 2019 +0200
+++ b/src/os/windows/vm/os_windows.cpp	Mon Jun 17 16:41:38 2019 +0100
@@ -1172,14 +1172,12 @@
     return dirp;
 }
 
-/* parameter dbuf unused on Windows */
-
 struct dirent *
-os::readdir(DIR *dirp, dirent *dbuf)
+os::readdir(DIR *dirp)
 {
     assert(dirp != NULL, "just checking");      // hotspot change
     if (dirp->handle == INVALID_HANDLE_VALUE) {
-        return 0;
+        return NULL;
     }
 
     strcpy(dirp->dirent.d_name, dirp->find_data.cFileName);
@@ -1187,7 +1185,7 @@
     if (!FindNextFile(dirp->handle, &dirp->find_data)) {
         if (GetLastError() == ERROR_INVALID_HANDLE) {
             errno = EBADF;
-            return 0;
+            return NULL;
         }
         FindClose(dirp->handle);
         dirp->handle = INVALID_HANDLE_VALUE;