Spot checked Windows 10 22H2 and all those functions were present in combase.dll, so looks safe so far.

Thanks, I also manually checked test_core and test_implement (which covers these functions) on Windows 10 so I think we should be good.

This broke Windows 7 support, which doesn't have combase.dll. Would it be possible to reintroduce the ole32.dll when building for the win7 target?

Hey @roblabla, we don't see sufficient value in adding additional complexity here to support Windows 7 at this time. (Sorry!)

Perhaps you can include a small forwarder with your target?

lib.rs:

macro_rules! stub {
    ($name:ident) => {
        #[allow(non_snake_case)]
        #[unsafe(export_name = stringify!($name))]
        pub extern "C" fn $name() {
            unreachable!()
        }
    };
    ($($name:ident),+ $(,)?) => {
        $(stub!($name);)+
    };
}

stub!(
    CoCreateFreeThreadedMarshaler,
    CoIncrementMTAUsage,
    CoTaskMemAlloc,
    CoTaskMemFree,
    RoGetAgileReference,
);

build.rs:

fn main() {
  println!("cargo::rustc-link-arg=/DEF:module.def");
}

module.def:

EXPORTS
    CoCreateFreeThreadedMarshaler=OLE32.CoCreateFreeThreadedMarshaler @865
    CoIncrementMTAUsage=OLE32.CoIncrementMTAUsage @919
    CoTaskMemAlloc=OLE32.CoTaskMemAlloc @963
    CoTaskMemFree=OLE32.CoTaskMemFree @964
    RoGetAgileReference=OLE32.RoGetAgileReference @1236