Postgresql 18beta1 and SPI changes

Dear members

We use are own version of DBmirror, we run our replication in a highly
fine grained manner. So every upgrade I have to make the code compile
and test. Up to PostgreSQL 17, I only got minor compilation problems
that I managed to resolve fairly easily. However this didn't prove to be
the case with PostgreSQL 18beta1, it proved harder to compile and as my
fears were verified, it has serious problems.

My question : is 18's SPI stabilized ? Can I start work on our version
of DBmirror ? Or wait for 18beta2 or -RC ?

Or is this not stabilized, which means there is a chance I found a
problem in postgresql's include system, so basically I contribute with
my test towards a 18beta2 or -RC ?

Sorry for not being more specific, my problems are far too many to start
asking more precise questions. After I get your opinion I will act
accordingly.