Native Extensions + Win32 + Clang



Since the release of 1.2.133 we now support building
the extensions for Windows with Clang.

It has some very good benefits:

  • We get a more unified pipeline
    • We can build all our platforms with the same compiler
  • Faster turnaround times for windows builds
    • The old build was about 10x slower on the extension server
  • Easier to develop cross platform extensions
    • You’ll write less platform specific code

How to use it

We’ve currently added a flag use-clang to control usage of the new compiler.
The current default value is false. You can add it to the app manifest like so:

            use-clang: true
            use-clang: true


We intend to phase out the old Windows build tools (CL.exe/LINK.exe) entirely in a few steps.

  • Currently
    • The special flag: use-clang can be added to test your extension for compatibility
    • Defaults to false
  • October 1’st
    • The default value is changed to true
  • (Preliminary: December 1’st)
    • We remove the flag altogether!

What does this mean for you?

Extension Developers

If you are a developer of an extension, make sure your extension builds with clang now to ensure that the end users can use the extension without disruption.

Extension Users

Ideally, you shouldn’t have to do anything at all.

But to make sure your native extensions will work with clang, it’s recommended that you use an app manifest and add this to your project, and also use the use-clang flag.

If you find that one of the native extensions you use doesn’t compile with clang, contact the developer of the extension and register an issue with them.

It might also be good to report non-working extensions here, so we can all keep track of progress.

How to create a Windows release build?


A gentle reminder that we’re nearing the switch to use clang as default compiler for WIndows builds.
I see on the server that there are still builds that take up to 5 minutes (!) and I’m hoping that those are using native extensions without even knowing it (it’s a powerful feature :slight_smile: ).

But, for those of you that maintain native extensions for Windows, please take a few moments to verify that your extension builds using clang. You can use the Manifestation tool to see how the use-clang flag is used.