Pike 8.0: Sql.pgsql objects don't get garbage collected?

Greetings,

I was testing out Roxen 6 on Pike 8, and I noticed a constantly increasing count of idle
connections to a Postgres database, while Roxen thought there were only a couple of connections.

I did a bit of testing, and it appears that a Sql.pgsql object does not get garbage collected
once all references are lost, and it stays active.

For a quick first test, I opened a database connection, and set a watch on the master_sql object,
then ran a gc.  The debug output showed a reference to the master_sql object during the run.


The test:

-=-=-=-
int main()
{
  Debug.gc_set_watch(Sql.Sql("pgsql://hungerf3@localhost:5432/hungerf3")->master_sql);
  gc();
}
-=-=-=-

The output:

-=-=-=-
## Watching thing 0x25b7770.
## Doing gc while watching for 1 things.
## Watched thing 0x25b7770 with 1 refs found in gc_mark_external() in pass 100.
marker at 0x241fa60: flags=0x1000000 refs=0 weak=0 xrefs=0 saved=-1 frame=(nil)
## Watched thing 0x25b7770 with 1 refs found in gc_is_referenced() in pass 200.
marker at 0x241fa60: flags=0x1080000 refs=0 weak=0 xrefs=1 saved=-1 frame=(nil)
## Watched thing 0x25b7770 with 1 refs found in gc_mark() in pass 200.
marker at 0x241fa60: flags=0x10c0000 refs=0 weak=0 xrefs=1 saved=-1 frame=(nil)
## Exiting gc and resetting watches for 1 things.
-=-=-=-

So the Sql.pgsql instance inside the Sql.Sql object never got garbage collected.

I did a bit more testing, with a weak reference to the master_sql object inside the
Sql.Sql object I was destroying.

Debug.locate_references found an active reference inside of pgsql_util:

**Function connectloop at /usr/local/pike/8.0.155/lib/modules/Sql.pmod/pgsql_util.pmod:365

Pike.identify_cycle found the following cycle:

({ /* 4 elements */
    pgsql(hungerf3@localhost:5432/hungerf3,11,0),
    Sql.pgsql,
    Pike.Backend(1),
    Stdio.File("socket", "localhost:5432", 777 /* fd=11 */)
})


My guess would be that the local backend inside of pgsql_util.pmod is holding on to the
connection object, and so it is not being garbage collected.

Has anyone else run into this?  I saw it on both Linux and FreeBSD with Pike 8.0.155.
Both were using AMD64 machine code, and talking to a PostgreSQL 9.5 database.

-Jeff