Question about implementing application compatibility

[Mislav Blazevic]

For past two weeks I've been implementing apphelp.dll. I got that one
working and moved onto kernel32 part of magic. According to various papers
and blogs it seems that windows logs all exes and dlls ever executed in
registry[1] and uses it as cache to lookup if binary needs to be shimmed or
patched (if file isn't found, hard lookup of shim database is done) It is
loaded on boot and saved back to registry on shutdown.

This is awfully overcomplicated (plus I do not know how to make such a
"global" variable in wine) so I was wondering is it OK to implement this
differently than windows does it. It would be simpler to control app compat
with environmental variable. It would mean that Base*Appcompat* kernel32
APIs would remain unimplemented but as far as I know, no application uses
them anyway, other than windows internally.

What do you think?

[1] https://github.com/mandiant/ShimCacheParser

[Vincent Povirk]

> This is awfully overcomplicated (plus I do not know how to make such a
> "global" variable in wine) so I was wondering is it OK to implement this
> differently than windows does it.

If the implementation does not have to be the same to preserve
compatibility, then you should ignore those details (ideally you
shouldn't know them at all). Certainly no real application should be
relying on a cache.

You can probably design it so the storage can be changed if it turns
out to be necessary.