add bindings for libpq

[usamoi]

add two header files:

• libpq/libpq.h
• libpq/pqformat.h

They are useful for a PostgreSQL type to implement send_function and receive_function.

[eeeebbbbrrrr]

Hi, @usamoi, would you mind rebasing this PR with develop? I just fixed CI there and I want to make sure things still build with the libpq headers included.

Looking at these headers, looks like they're mostly a combination of #defines and static inlines. I wonder if what we actually need here is to hand-port these to rust?

What symbols from these headers are you trying to get access to?

[usamoi]

Hi, @eeeebbbbrrrr. I need symbols including pq_begintypsend, pq_endtypsend, pq_sendbytes and so on. They are used for send/recevie function of a Postgresql type, eg. https://github.com/postgres/postgres/blob/REL_16_STABLE/src/backend/utils/adt/varlena.c#L617.

[eeeebbbbrrrr]

Hi, @eeeebbbbrrrr. I need symbols including pq_begintypsend, pq_endtypsend, pq_sendbytes and so on.

I see. Because they're static inline this won't pull in some of the other helper functions like pg_write[int32, int64, int16, int8], etc. :(

So I'll just note here that we may need to port those to run at some point (and would happily accept a PR!).

Once you rebase and we can confirm CI passes, I'll merge this. I was thinking of doing another release on Monday or Tuesday.

[eeeebbbbrrrr]

1: clang diagnosed error: /usr/include/postgresql/15/server/libpq/libpq-be.h:34:10: fatal error: 'gssapi/gssapi.h' file not found

I was worried about something like this.

I think this header is related to Kerberos. It's being pulled in through the new libpq.h. I would expect ENABLE_GSS to not be defined for the Postgres that pgrx compiles/installs.

Do you need libpq.h too?

[usamoi]

I think I don't need libpq.h really. Deleted it.

[eeeebbbbrrrr]

I think I don't need libpq.h really. Deleted it.

Yeah. I was getting concerned about potentially adding another development requirement on Kerberos.

Assuming the latest ci job passes, I’ll merge and get a new release out early next week.

Thanks for your efforts on this Saturday afternoon!