Re: Need help with COM dll registration at runtime

From:
"Igor Tandetnik" <itandetnik@mvps.org>
Newsgroups:
microsoft.public.vc.language
Date:
Mon, 12 Mar 2007 11:04:14 -0400
Message-ID:
<upwKkfLZHHA.4264@TK2MSFTNGP05.phx.gbl>
Suman <skarpio@gmail.com> wrote:

I'd love to know about these better ways. Would you mind sharing a
couple
of pointers along those lines?


Read about ATL.

http://www.codeproject.com/atl/SimpleATLCom.asp
http://msdn2.microsoft.com/en-us/library/599w5e7x.aspx

           fscanf(fp, "CLSID=%s%*", out);


%* is not a valid format specifier. Does this function succeed? Do
you get expected CLSID when this function returns?

From the [*]scanf man page:

* Suppresses assignment. The conversion that follows occurs as
             usual, but no pointer is used; the result of the
conversion is
             simply discarded.


It's a flag in another format specifier, it can't be used on its own.
It's used like this: "%*s" .

I guess fscanf simply ignores the ill-formed sequence.

In fact, my interface file has this:

// Our interface implementor object's GUID
// {1A1E2B69-CAF0-4f6d-B08E-6B69D3355E84}
DEFINE_GUID(CLSID_IPTPlugin,
0x1a1e2b69, 0xcaf0, 0x4f6d, 0xb0, 0x8e, 0x6b, 0x69, 0xd3, 0x35, 0x5e,
0x84);

Iff, instead of ri, or some variable where I have copied the CLSID
from the file,
I use this CLSID_IPTPlugin, the code works like a charm.


Well, that means there's a component registered for
{1A1E2B69-CAF0-4f6d-B08E-6B69D3355E84}. But is there a component
registered for {70108A03-F9E4-4a88-8654-45483B9ADC9C} ?

Which leads
me to
think that I am having problems retrieving the CLSID, until and unless
there is
some rule that says, you have to use the identifier declared in the
interface's
header (CLSID_IPTPlugin in this case) and not anything else
(e.g:pluginCLSID).


CoGetClassObject takes a GUID - basically a block of 16 bytes. It
doesn't care how you obtained those bytes - whether you hardcoded them
in your executable, or read them from some file. All it cares about is
that it should look in the registry under the key whose named is
determined by this CLSID, and be able to find the path to the DLL, load
that DLL, call DllGetClassObject in it, and obtain an interface pointer.

int CustomRegister(REFCLSID ri/*HINSTANCE hinstExe, HINSTANCE
hinstPrev, LPSTR lpszCmdLine, int nCmdShow*/)
{
// Create a subkey whose name is the ascii string that represents
// our IPTPlugin2 object's GUID
stringFromCLSID(&buffer[0], (REFCLSID)(CLSID_IPTPlugin)/* ri*/);


You seem to be hard-coding CLSID_IPTPlugin into the registry key name,
and ignoring the parameter passed to CustomRegister.

Well as I explained in my previous post, I was trying to have the dlls
registered
when they are used.


You don't actually need to register a DLL in order to use it. See

http://www.koders.com/cpp/fidBF997508BE1FC6B75E067FB170401C831EA9D858.aspx?s=http

the part in LoadExternalObject that starts with a call to CoLoadLibrary.
--
With best wishes,
    Igor Tandetnik

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