Thanks Ehsan, this is a lot easier than setting breakpoints in the ATL
code. However I have a small problem with this; all 'known' interface
name (IUnknown, ...) are printed ok but my own interface aren't
displayed - I get something like this:
CMyClass - IUnknown
CMyClass- IMarshal - failed
CMyClass- - failed
CMyClass- IUnknown
CMyClass- IStdMarshalInfo - failed
CMyClass- IExternalConnection - failed
CMyClass- - failed
CMyClass-
That last line is my own interface (I saw the iid in the debugger) but
I'm not sure what the two failed ones are (they have a guid that is not
in my program nor in the idl that I got that describes my 'black box'
object). So I'd like to see a name, any idea on how to do that?
Also, I have a question what my COM_MAP should look like. I have this:
BEGIN_COM_MAP(CMyClass)
COM_INTERFACE_ENTRY(IMyClass)
COM_INTERFACE_ENTRY(ISomeBaseClass)
COM_INTERFACE_ENTRY(ISomeBaseClass2)
END_COM_MAP()
where ISomeBaseClass2 is derived from ISomeBaseClass and IMyClass is
derived from ISomeBaseClass. Do I need to put them all in the COM_MAP or
are the first two enough? Thanks.
cheers,
roel
-----Original Message-----
From: Ehsan Akhgari [mailto:[EMAIL PROTECTED]
Sent: Tuesday, October 12, 2004 21:13
To: [EMAIL PROTECTED]
Subject: RE: [msvc] finding out which interface is requested from a ATL
control
I'm still taking baby steps into COM and ATL and I've run into my next
problem. I'm writing a server that is instantiated by an executable for
which I have no source code. I can trigger the executable to create an
instance of my server; when something goes wrong, the only error message
I get from that executable is the COM error code. I'm past the stage
where I kept getting 'class not registered', so that's good; thing is, I
now get 'interface not supported'. I do have an IDL file with a bunch of
COM interfaces but I don't have any documentation on which interface I
should implement (and how). So my first idea was to override the
QueryInterface() method in my ATL object and log the contents of the
riid parameter to a file. I hacked the END_COM_MAP macro a bit and it
compiled ok but when I triggered my blackbox executable I got the
'interface not supported' again (as was to be expected) but worse, no
file was created (so my QueryInterface function on the ATL object wasn't
called). Now I was thinking, maybe I should first try to override the
QueryInterface of my CoClass and see if that works? But how would I do
that? Is there maybe another way for me to find out which interface is
requested? Thanks.
This is a common problem in creating ATL objects, and like all common
problems in this task, ATL comes to rescue.
ATL has some built-in debugging support. One of them is the
_ATL_DEBUG_QI macro. Just #define this macro before all ATL headers (at
the top of stdafx.h if you use it) and recompile. ATL will trace all
calls to QueryInterface( ) on all interfaces for you automagically in a
useful manner.
But you will have lots of problems if there's no doc on the interfaces
you must implement. Each interface has a purpose, and each method has a
purpose too. It's tough to guess them all over on your own. And it's
prone to any number of errors. The least thing that they should provide
for you is a commented IDL with helpstring's all over the place, but
that wouldn't replace a nicely written piece of documentation.
---------
Ehsan Akhgari
www.farda-tech.com
List Owner: [EMAIL PROTECTED]
[Email: [EMAIL PROTECTED]
[WWW: http://www.beginthread.com/Ehsan ]
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