Eric's Complete Guide To Type Signatures Of Scriptable Object Models

re: Eric's Complete Guide To Type Signatures Of Scriptable Object Models

Kim Gräsman — Wed, 14 Jul 2004 20:24:00 GMT

"There are memory leaking scenarios for VBScript."

I've been experimenting with this lately (ten years too late, I guess).

Is this not just a simple bug? Why not make sure value going into [out] parameters are properly released?

Come to think of it, probably because you can't know it's [out], since you don't read the typelib - is that it?

Thanks for any definitive answers.

re: Eric's Complete Guide To Type Signatures Of Scriptable Object Models

Eric Lippert — Wed, 14 Jul 2004 21:38:00 GMT

Correct. The script engine has no idea whether it is talking to an out, in, or in-out parameter. The script engine sees

foo.bar baz

and thinks "clearly the developer wishes me to pass a reference to baz", so that's what it does.

The callee on the other hand knows that the contract is "this thing is an out parameter, so I don't have to free the thing that comes in."

The problem is as you state -- there's no way for the engine to know what the contract is before the call without checking the type info, and that is VERY expensive in some common scenarios.

re: Eric's Complete Guide To Type Signatures Of Scriptable Object Models

Alex Angelopoulos — Wed, 14 Jul 2004 22:42:00 GMT

> ... there's no way for the engine to know what the contract is before the call without checking the type info, and that is VERY expensive in some common scenarios.

Dang. You stole my thunder. I was about to wax eloquent on the beauties of using tlbinf32.dll to assist scripting... :|

re: Eric's Complete Guide To Type Signatures Of Scriptable Object Models

Chris Kunicki — Thu, 15 Jul 2004 18:47:00 GMT

Eric, as always, interesting stuff. Dude, when you going to blog about VSTO 2? (assuming you're still working with that team, maybe not?)

re: Eric's Complete Guide To Type Signatures Of Scriptable Object Models

Eric Lippert — Thu, 15 Jul 2004 18:52:00 GMT

Thanks dude!

I am still working on VSTO2.

Eric Carter, Peter Torr, Paul Stubbs and the VSTO User Education team are all blogging about it, and I reserve the right to do so as well, and I probably will at some point.

However, one of the primary reasons I started this blog is because the COM script engines are still widely used and will be widely used for some time. I have a huge email archive containing trivia about the script engines that exists nowhere else on the web, and still lots of questions to answer in public, so I'm going to stick primarily to scripting for some time yet.

re: Eric's Complete Guide To Type Signatures Of Scriptable Object Models

Marcus Tucker — Mon, 19 Jul 2004 11:38:00 GMT

>However, one of the primary reasons I started this blog is because the COM script engines are still widely used and will be widely used for some time. I have a huge email archive containing trivia about the script engines that exists nowhere else on the web, and still lots of questions to answer in public, so I'm going to stick primarily to scripting for some time yet

Keep going! Great stuff so far! Thanks Eric...

Shell Extensions for .NET Assemblies, Version 1.4.1993

Heath Stewart's Blog — Thu, 12 Oct 2006 07:08:25 GMT

Version 1.4.1993 of the Shell Extensions for .NET Assemblies has been released.

re: Eric's Complete Guide To Type Signatures Of Scriptable Object Models

Jason Roberts — Fri, 05 Jan 2007 17:35:38 GMT

Eric -- your blog rocks. I never thought I would return to COM automation and scripting but it is still the easiest way to reach the rest of the world that is not on the .Net bandwagon. Thanks for putting all the useful details up.

I have one question that perhaps you could treat as a follow-on to this blog entry: discussion of [in, defaultvalue] vs. [in, optional] in IDL and the various scripting engines and .Net COM interop. I recall you having an entry on optional parameters but now I can't find it; in any case I don't remember it discussing the distinction between [optional] and [defaultvalue]. It is not super clear why both exist and what the differences are between them. For example, older COM books say you can specify [in, optional, defaultvalue] for parameters, but the present-day MIDL compiler does not let you do it. [optional] and [defaultvalue] are mutually-exclusive.

Thanks again man, this stuff is great!

Calling functions of COM object from JScript

Visual Studio to Internet Explore... — Fri, 10 Aug 2007 21:26:01 GMT

To be able to invoke functions on the instantiated COM function through JScript, we need to add the method to the ITest interface which is derived from IDispatch.