Debuging while using Smarty template engine came up with the problem that xdebug seems to url-encode filenames. Smartys compiled templates are in the form:
%%82^823^823B39A1%%layout.tpl.php

Xdebug tries to open and send to the client a file by name:
MyTitle Warning: main(/srv/www/vhosts/myhost/htdocs/templates_c/%?^823^823B39A1%%layout.tpl.php): failed to open stream: No such file or directory in /srv/www/vhosts/myhost/htdocs/templates_c/%%82^823^823B39A1%%layout.tpl.ph:

Second % sign and number 82 gets converted to some garbage.
When opening files, names should not be passed through usefulstuff.c:xdebug_raw_url_encode, called from xdebug_handler_dbgp.c:xdebug_path_from_url, called from return_file_source (?).

PHP 5.2.9, Xdebug 2.0.4, host is Linux (Opensuse 11.1)