Re: charin(), text_char() should return something else for empty input

I wrote:
> I propose that both of these operations should return a space character
> for an empty input string.  This is by analogy to space-padding as you'd
> get with char(1).  Any objections?

An alternative approach is to make charin and text_char map empty
strings to the null character (\0), and conversely make charout and
char_text map the null character to empty strings.  charout already
acts that way, in effect, since it has to produce a null-terminated
C string.  This way would have the advantage that there would still
be a reversible dump and reload representation for a "char" field
containing '\0', whereas space-padding would cause such a field to
become ' ' after reload.  But it's a little strange if you think that
"char" ought to behave the same as char(1).

Comments?
        regards, tom lane