add nothrow and @nogc to windows files

[WalterBright]

blocking dlang/dmd#13960

[dlang-bot]

Thanks for your pull request, @WalterBright!

Bugzilla references

Your PR doesn't reference any Bugzilla issue.

If your PR contains non-trivial changes, please reference a Bugzilla issue or create a manual changelog.

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + druntime#3796"

[dkorpel]

This turns callback types nothrow nogc as well, which is a breaking change. That might be fine, but worth considering.

[rainers]

This turns callback types nothrow nogc as well, which is a breaking change. That might be fine, but worth considering.

Yes, something to keep an eye on, but in this case the function types seem to be meant as types of the respected functions, e.g. to be used for casting the result of GetProcAddress("DllGetClassObject").

The change in unknwn.d doesn't change the interfaces (which would be too restrictive for implementing classes), so that won't help making vsoptions.d nothrow in dlang/dmd#13960.

[WalterBright]

https://devblogs.microsoft.com/oldnewthing/20200911-00/?p=104205 suggests that COM interfaces are nothrow. They're also designed to be used with C, which doesn't throw.

[rainers]

Indeed, the STDMETHOD macro contains __declspec(nothrow) by default (can be disabled with a preprocessor define), but the IUnknown interface doesn't include it. Adding it is probably intended, but will break code now because overriding methods are unllikely to be annotated.

Not allowing arbitrary allocations with @nogc is more restrictive, though.

[WalterBright]

@rainers what prompted this is I can't get dmd source code to be nothrow because some of it calls code in unknwn.d and vsoptions.d.

(Also, the AddRef and Release functions were designed before exception handling came about, and they obviously won't work with exceptions flying around.)

[rainers]

I understand what you are trying to do but

• the change here isn't good enough, you will have to add nothrow @nogc: inside the interface declarations, too.
• dmd is compiled with older versions, too, so it might take a while until the change is usable inside dmd

I forgot that attributes are inherited by overriding functions automatically, so that restricts breakage to implementations of these methods that call unannotated functions. I'm fine with updating my sources (though most use a different translation of the Windows headers anyway), but I suspect there will be some breakage.

[WalterBright]

I rebooted this as #3797