function is the wide-character equivalent of the
It pushes back a wide character onto stream and returns it.
If wc is WEOF, it returns WEOF.
If wc is an invalid wide character,
it sets errno to EILSEQ and returns WEOF.
If wc is a valid wide character, it is pushed back onto the stream
and thus becomes available for future wide-character read operations.
The file-position indicator is decremented by one or more.
indicator is cleared.
The backing storage of the file is not affected.
Note: wc need not be the last wide-character read from the stream;
it can be any other valid wide character.
If the implementation supports multiple push-back operations in a row, the
pushed-back wide characters will be read in reverse order; however, only one
level of push-back is guaranteed.
function returns wc when successful, or WEOF upon
The behavior of
depends on the
category of the