Re: passing arrays to shared object functions

Jason Nerothin wrote:
> I've been attempting for a while to figure out how to pass arrays of
> integers back and forth from a custom c-library that I'd like to plug into
> my server instance. Although I'm able to usefully pass single integers to a
> functions I've written, the best I've been able to accomplish passing in
> pointers and const pointers is to blow up the server. I've only attempted
> compiling per the instructions <a href="
> http://www.postgresql.org/docs/current/static/xfunc-c.html">here</a>. I
> wanted to check with this list first before spending any time delving into
> libpq for fear that it was the wrong rabbit-hole to go looking into in the
> first place.

arrays are not passed as pointer-to-the-first-element to your c function
as they are in plain C. There are macros defined in the postgres headers
for dealing with arrays - I suggest that you look at some backend
functions that take parameters, and see how they handle things. (I think
grepping for array_concat might give you a clue of where to look...).

At least for "version 1" functions, even ints and such are not passed
as normal parameters to your function - there are macros for accessing
such parameters too.

greetings, Florian Pflug