[Mono-dev] OracleClient.Oci and GC

[Neale Ferguson]

Thanks. I've made changes to OciDefineHandle and have cured nearly all the failures I had been experiencing. I have started on OracleParameter as it has an object called indicator that is used by the OCIBindxxx calls and appears to suffer from the same problem. I was allocating the object in native memory in the constructors and was going to free them in a destructor. However, in my test runs I see I'm allocating 1200+ objects but only freeing ~900. Would you elaborate on your final comment "failing to dispose..." as I'm reading this as I don't need to Marshal.FreeHGlobal() the object I allocated in the constructors.

Neale

On Aug 22, 2014, at 11:31 AM, Rodrigo Kumpera <kumpera at gmail.com> wrote:

> Hey Neale,
> 
> You can safely pass interior pointers to pinvoke without fearing the object been collected for the duration of the call.
> Mind that you have to correctly use specify in/out/ref depending on the copy semantics you need.
> 
> Problems only arise when native keeps that pointer after the call finishes, this can result in the object been moved
> as the GC has no visibility into the native heap.
> 
> For those cases you can either create a pinning GC handle to the victim object or you can allocate a chunk of native
> memory that will be shared between managed and native to store the desired value. Both options suck, TBH.
> 
> I'd say go with the native chunk of code if you can't lexically scope the pinning regions, it will be more reliable as
> failing to dispose the object won't lead to permanent leaks.