On Wednesday, 27 January 2021 at 13:39:32 UTC, SealabJaster wrote:
The biggest one for me, is that RTTI isn't "shared" across
boundaries.
Yeah, that's a big one. Exception handling tables are also not
properly merged leading to random behavior even if you do manage
to catch the exception (I wrote a PR for that but it isn't
theoretically sound https://github.com/dlang/druntime/pull/2874#
), the GC proxy is done wrong - but there might be a chance to
fix that - and there's a bug with static data not being scanned.
Possibly related to the GC proxy, not sure.
It is all related to the same root problem - on Windows, unlike
Linux, symbols are not automatically merged. More info
http://dconf.org/2016/talks/thaut.html
Yes, from 2016. And a branch aiming to fix it:
https://github.com/ingrater/dmd/tree/DllSupportD
So what happens is if you have a global variable in the dll and
exe, each one has their own copy of it. So typeid are not merged,
GC meta is not merged. druntime tries to hack around this but it
doesn't do a good job.
But then in user libs the same thing happens and they almost
never make any attempt to handle it, so if you using other stuff,
there be dragons. It might be perfectly fine, separate copies of
data is often not fatal at all. But if they expect sharing - you
can get separate singletons and such - you're in some trouble.
Technically what dmd does for dlls isn't wrong. That is the way
the underlying operating system works. But since it is more
useful to handle these things and the Microsoft C++ compilers
paper over this with auto-generated indirection, even Windows
programmers might not realize it and it just seems completely
broken.
(btw as for me fixing it myself, there's a number of subtleties
that I don't even know. Maybe i could figure them out but the
fact is it is prolly gonna be a buggy transition. But the most
discouraging part is seeing all that talk and code from 2016 just
sitting there, ignored. What's the point of even trying if it is
just going to rot again.)
