[utils] setproctitle: Fix NUL termination (#17724)

Authored by: doe1080

test/test_utils.py

@@ -107,6 +107,7 @@ from yt_dlp.utils import (
     sanitize_filename,
     sanitize_path,
     sanitize_url,
+    setproctitle,
     shell_quote,
     strftime_or_none,
     smuggle_url,
@@ -613,6 +614,14 @@ class TestUtil(unittest.TestCase):
         self.assertEqual(res_url, url)
         self.assertEqual(res_data, {'a': 'b', 'c': 'd'})
 
+    @unittest.mock.patch('ctypes.cdll.LoadLibrary')
+    def test_setproctitle(self, load_library):
+        for title in ('yt-dlp', 'café'):
+            with self.subTest(title=title):
+                setproctitle(title)
+                buf = load_library.return_value.prctl.call_args.args[1]
+                self.assertEqual(bytes(buf), title.encode() + b'\0')
+
     def test_shell_quote(self):
         args = ['ffmpeg', '-i', 'ñ€ß\'.mp4']
         self.assertEqual(