Use print_char('x') instead of print_string("x").
[cparser] / lextest /
drwxr-xr-x   ..
-rwxr-xr-x 246 do_tests.sh
drwxr-xr-x - legalc
drwxr-xr-x - preprocessor
drwxr-xr-x - tokenstreams
drwxr-xr-x - warnings