Using timestamp(tz) in C functions

Working on trying to get a C version of the maintenance function for my
pg_partman extension working so I can hopefully make it more flexible and
efficient.

https://github.com/keithf4/pg_partman/blob/master/sql/functions/run_maintenance.sql

Up until this point I've just been using SPI and the Datum conversion
functions (DatumGetCString, DatumGetInt32) to get string and numeric data
out of tables and things have been working fine. I'm at the first point in
that function where I'll need to start dealing with timestamp data.

https://gist.github.com/keithf4/81c32bf8b689c74b20c10ad8c91d45a3#file-pg_partman_bgw-c-L532

There's what I've got working so far and links directly to the area where
I'm having a problem. I found the DatumGetTimeTzADTP() function and the
TimeTzADT data type looking through the source and that seems to be exactly
what I'm looking for. However, when I get to the point of trying to simply
use the time value in that variable (line 544), Postgres segfaults. So far
I've just been trying to print the value out to the log to ensure I'm
pulling it out correctly. The "time" value of the struct appears to be an
int64, so I thought %ld would be the correct, but even using %d or %s fails.

You can see in my original plpgsql function how I eventually intend to use
the timestamp values. Here's a link directly to the equivalent section

https://github.com/keithf4/pg_partman/blob/master/sql/functions/run_maintenance.sql#L139

So, not sure if I'm even going about this the right manner for the way I
intend to use the timestamp values. Still fairly new to C and getting use
to postgres internals. Any help, or even an example of using timstamp data
pulled from a table in C with SPI, would be great.

Thanks!

--
Keith Fiske
Database Administrator
OmniTI Computer Consulting, Inc.
http://www.keithf4.com