Could not compile or run UWP branch targeting thumbv7a-uwp-windows-msvc

[bdbai]

As I am trying building with target thumbv7a-uwp-windows-msvc, compilation failed:

error[E0570]: The ABI `"stdcall"` is not supported for the current target
  --> C:\Users\bdbai\.cargo\registry\src\github.com-1ecc6299db9ec823\com-0.2.0\src\interfaces\iclass_factory.rs:12:1
   |
12 | #[com_interface("00000001-0000-0000-c000-000000000046")]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0570]: The ABI `"stdcall"` is not supported for the current target
 --> C:\Users\bdbai\.cargo\registry\src\github.com-1ecc6299db9ec823\com-0.2.0\src\interfaces\iunknown.rs:8:1
  |
8 | #[com_interface("00000000-0000-0000-C000-000000000046")]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

It looked like a problem with com-rs and had been reported (see microsoft/com-rs#92 (comment)). Then I checked out the commit before using com-rs at 946a74, a similar error came out:

error[E0570]: The ABI `"stdcall"` is not supported for the current target
 --> src\uwp\interop.rs:2:1
2 | / extern "stdcall" {
3 | |     fn RoInitialize(init_type: RoInitType) -> winrt::ErrorCode;
4 | | }
  | |_^

Fixed by changing stdcall to system. After that, I managed to package and deployed it to a ARM device, a panic immediately occurred without previous stack trace.

(A screenshot of the call stack recovered from a minidump)

Further investigation is required to make it run on an ARM device.

[robmikh]

Thanks for trying this out! I wonder if this is also the case with ARM64, I can give that a try over the weekend.

The problem with using the pre-com-rs version is that it's mainly duct tape and paper clips (I heavily mutilated some of the stuff you were doing in your firstuwp-rs project, it was a great help!). We might have to experiment with a modified version of com-rs, or wait for implementing types to be supported in Rust/WinRT.

[robmikh]

Well, unfortunately after switching to a new machine and a newer version of Visual Studio 2019, I'm no longer able to build the rust toolchain. It looks like there's an issue building llvm, hopefully it gets resolved soon and I can look at this again.

I seem to be having the same problem this person is: https://users.rust-lang.org/t/rust-bootstrap-fails-on-windows/45162

[bdbai]

Well, unfortunately after switching to a new machine and a newer version of Visual Studio 2019, I'm no longer able to build the rust toolchain.

Try Xargo instead? It only requires a nightly toolchain.

[robmikh]

This is mainly for my own tracking, but the issue of compiling llvm with MSVC seems to be recorded here:
https://bugs.llvm.org/show_bug.cgi?id=47160

[robmikh]

To finally close the loop on this, I gave this a try again and it worked.