Re: How to manage shared library lifetime through C functions

From: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
To: Seref Arikan <serefarikan(at)gmail(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: How to manage shared library lifetime through C functions
Date: 2014-08-04 10:58:04
Message-ID: 53DF673C.7090508@vmware.com
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On 08/04/2014 01:31 PM, Seref Arikan wrote:
> Thanks a lot Heikki and Albe. Exactly what I was asking for.
> Heikki: the libraries are written in languages that have their own runtime
> and their documentation insists that both init and dispose calls are
> performed when used from C. PG_init() and proc_exit sounds spot on.

You might also consider creating your own PL handler for those
languages. Or google around if one exists already.

> Any ideas about keeping some data at session level between calls? Both
> calls of the same function and different C functions. (though temp table is
> always there as an option)

You can use a global variable in the C extension. If you need to
allocate memory that survives across function calls, use
"MemoryContextSwitchTo(TopMemoryContext); ... = palloc(...)". I'm sure
you'll find examples of that in the existing extensions too.

- Heikki

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