From 1a1db4d1f804ca724218b3bb9e00d0ad7b1ed34a Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Tue, 11 Jun 2019 16:35:29 +0530
Subject: [PATCH] Ensure no trailing NULLs in result of file_association()

---
 src/calibre/utils/windows/wintest.py    | 4 +++-
 src/calibre/utils/windows/winutilpp.cpp | 4 ++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/calibre/utils/windows/wintest.py b/src/calibre/utils/windows/wintest.py
index 8a0c0521d5..aad2c7b5dc 100644
--- a/src/calibre/utils/windows/wintest.py
+++ b/src/calibre/utils/windows/wintest.py
@@ -24,7 +24,9 @@ class TestWinutil(unittest.TestCase):
         self.winutil.add_to_recent_docs(path, 'some-app-uid')
 
     def test_file_association(self):
-        self.assertIn('notepad.exe', self.winutil.file_association('.txt'))
+        q = self.winutil.file_association('.txt')
+        self.assertIn('notepad.exe', q.lower())
+        self.assertNotIn('\0', q)
         self.assertIsNone(self.winutil.file_association('.mkjsfks'))
 
     def test_special_folder_path(self):
diff --git a/src/calibre/utils/windows/winutilpp.cpp b/src/calibre/utils/windows/winutilpp.cpp
index 741804e0d5..5cee908e76 100644
--- a/src/calibre/utils/windows/winutilpp.cpp
+++ b/src/calibre/utils/windows/winutilpp.cpp
@@ -68,8 +68,8 @@ file_association(PyObject *self, PyObject *args) {
 	if (!PyArg_ParseTuple(args, "O&", py_to_wchar, &ext)) return NULL;
 	HRESULT hr = AssocQueryStringW(0, ASSOCSTR_EXECUTABLE, ext, NULL, buf, &sz);
 	free_wchar_buffer(&ext);
-	if (!SUCCEEDED(hr)) Py_RETURN_NONE;
-	return Py_BuildValue("u#", buf, (int)sz);
+	if (!SUCCEEDED(hr) || sz < 1) Py_RETURN_NONE;
+	return Py_BuildValue("u", buf);
 }
 
 PyObject *