Hello,
I'm studying Julia and I'm trying to write a libpq (PostgreSQL) wrapper.
The C PQconnectdb function starts a PostgreSQL connection, and returns a
pointer to the connection struct. The connection struct is not exposed by
libpq, since it is not useful.
When the connection finishes, it must be closed using the C function
PQfinish which, among other things, takes care to free the struct memory.
So I guess I should call the PQfinish function when the connection get
finalized by the GC, which this is the purpose of the following code (Julia
version: 0.3.0-744~ubuntu13.10.1):
module LibPQ
typealias PGconn Ptr{Void}
function pgconn_finalizer(x::PGconn)
ccall( (:PQfinish, "libpq"), Void, (PGconn,), x )
println("finalized")
end
c = ccall( (:PQconnectdb, "libpq"), PGconn, (Ptr{Uint8},), "connection
params" )
finalizer(c, pgconn_finalizer)
println(c)
gc()
end
But I get this error:
$ julia libpq.jl
ERROR: objects of type Ptr{None} cannot be finalized
in finalizer at base.jl:103
in include at boot.jl:240
while loading ./libpq.jl, in expression starting on line 12
I guess I should use another type for the PGconn typealias, but I can't
figure out what type. Any idea?
Thank you :-)
