Re: DLL and synchronizing global data

From:

"Bruno van Dooren [MVP VC++]" <bruno_nos_pam_van_dooren@hotmail.com>

Newsgroups:

microsoft.public.vc.language

Date:

Wed, 20 Sep 2006 22:55:12 +0200

Message-ID:

<ub3hWcP3GHA.480@TK2MSFTNGP06.phx.gbl>

Well at the moment in DllMain(), I am calling CoInitialize()

Evil. Don't do this. It is not safe.

and instantiating an MSXML Dom object (which loads MSXML6.DLL) to help
initialize the DLL data, seems to work fine!

Could be. And suddenly, if the user starts wearing green pants on friday
(but only if it's raining) your app will mysteriously fail.
That's the problem with undefined behaviour. It is not safe. It might work
99% of the time, but not always.

Still in light of all this I think I will make the DLL global data, static
class data instead.

The same rules apply to all code that is executed due to global construction
/ destruction of objects.
It is not safe to do complex initialization / cleanup that way. It may work
most of the time, but it isn't safe.

I have seen some weird problems that were caused by violation of these
rules.
They took quite some time to track down as well.

--

Kind regards,
    Bruno van Dooren
    bruno_nos_pam_van_dooren@hotmail.com
    Remove only "_nos_pam"