Denis Zaitsev <zzz@cd-club.ru> writes:
> So, I create some new scalar type and I don't declare its in/out
> functions as STRICT. But PostgreSQL copes with them such as they
> would be STRICT - they never get the NULL value.
This is likely true in many places --- for example, COPY has a shortcut
because it wants to substitute \N for nulls. It would not be a bright
idea to assume that it's true in every place and forevermore. In
general, if you have a C function and don't want to be bothered with
explicit PG_ISNULL testing, you'd better mark it STRICT.
An example of an easy way to crash an I/O function without such guards
is to invoke it explicitly:
regression=# select textin(null::cstring);textin
--------
(1 row)
regression=# select textout(null::text);textout
---------
(1 row)
regards, tom lane