A call to setlocale with no second argument is documented to be a read-only operation, querying the current locale configuration. In fact it has a side effect of setting the encoding on primordial ports:
$ guile-2.0 -c '(write (port-encoding (current-input-port))) (newline) (setlocale LC_TIME) (write (port-encoding (current-input-port))) (newline)' #f "ANSI_X3.4-1968" Observe that this occurs even if the locale reading operation is for a category unrelated to character encoding. The actual decoding behaviour of read-char is altered in accordance with the reported encoding. Non-primordial ports opened before or after the setlocale call are not affected. -zefram
