Re: passing variant safearray

"Igor Tandetnik" <>
Mon, 10 Jul 2006 13:15:56 -0400
bob <> wrote:

I use the following idl code to pass bytes of data to a COM object
marked oleautomation:

[id(3), helpstring("method Receive")] HRESULT Receive([in] VARIANT

the client does the following:
1 create safearray
2 fill the array
3 init variant and set type an parray
4 call Receive on the object passing in the variant
5 call variantclear

in the Receive method I access the safearray but don't clean it up as
the client is doing already.
Is this right?

Yes, this is right.

Also am I right in thinking that the safearray packed in the variant
is actually never copied. So effectively passed by reference?

Yes. Except of course when the call is made across process or machine

If that's right then must I be careful to call Receive in this way in
a MTA situation?

In the scenario you describe, I don't see any possibility of concurrent
access, in MTA or otherwise.

Is there a better way? I sometimes get corrupt safearrays across and I
think it is because the client clears the variant too soon.

Client clears the variant only after the call returns. Server controls
when that happens. I don't see how the client can clear the array "too
soon". Unless of course the server does something illegal like caching
the pointer passed as [in] parameter.
With best wishes,
    Igor Tandetnik

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land, and it could be dangerous sitting under them as they fly
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