Re: Using a Windows DLL in Delphi

From:

"William DePalo [MVP VC++]" <willd.no.spam@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Thu, 18 Oct 2007 10:43:00 -0400

Message-ID:

<#BHnwUZEIHA.3332@TK2MSFTNGP04.phx.gbl>

<ulf_honkanen@yahoo.com> wrote in message
news:1192717770.622557.188270@q5g2000prf.googlegroups.com...

Sorry for the (kind off OT), but I'm trying to translate the headers
for vssapi.dll to use the dll with Delphi. Almost everything is fine
and dandy, but when trying to use "CreateVssBackupComponents", I see
that the MSDN entry indicates that the function is exported as
"CreateVssBackupComponentsInternal". This is true in the Vista version
of the dll.

In older versions (Xp and 2003) the funnction was exported as

"?CreateVssBackupComponents@@YGJPAPAVIVssBackupComponents@@@Z" In
vista the function is ALSo present with that name.

Is it "safe" to use GetProcedure Address with that long name, seeing
that the name has not changes in all three versions (only a new alias
was added)? I know nobody can be 100% sure, but is this a safe guess?
Why are there a lot of exported function in this dll with those
unfriendly names? If not an API supposed to be clear?

You are treading on thin ice if you call the function with the long name. I
used the undname utility to undecorate that name to show this signature

long __stdcall CreateVssBackupComponents(class IVssBackupComponents **)

In case you don't know, C++ decorates (some would say mangles) names to
enforce type safe linkage. And in general trying to use a binary that
contains a class from an executable created with another tool is unsafe. It
may work if the author had an eye toward portablility and exported a COM
like interface but you can't complain if it doesn't do what you want or
blows up rudely.

Regards,
Will