[bug] Missing watchOS arm64 architecture

[djavan-bertrand]

Describe the bug
When building for watchOS (WATCHOS or WATCHOSCOMBINED) and using the lib in Xcode, the Xcode build fails because architecture arm64 is not found.

To Reproduce
Steps to reproduce the behavior:

1. Build using WATCHOS platform flag
2. Embed the dylib in a xcframework
3. Use this xcframework in a Apple Watch target in Xcode.

=> Xcode fails with undefined symbols and a warning:

ignoring file 'PATH/MY_LIB.dylib': fat file missing arch 'arm64', file has 'armv7k,arm64_32'

Expected behavior
The Xcode build should succeed

Solution found
Even though I am not sure it is the correct way to do so, here is how I fixed this bug:
I replaced line 450 of the ios.toolchain.cmake script with:

set(ARCHS arm64 armv7k arm64_32)

(instead of set(ARCHS armv7k arm64_32))
If it is the correct way, do not hesitate to tell me, I can submit a PR for you.

Environment

• CMAKE: 3.29.2

[leetal]

Thanks for reporting this, albeit a late response from me, but I struggle to find any references if apple have changed/added the arm64 architecture to the platform. At least previously the only available 64 bit arm arch was the 32 bit pointer+64 bit registers variant arm64_32…

Had you any simulator slices added to the xcframework? Because I really think that arm64 is not a strict requirement (I even think it would be bad since full arm64 consumes more RAM than arm64_32… so why would they want to change that?)

[MyOwnClone]

Hello, thanks for a very cool project!
I experienced the exact same problem as reported above when building for my Watch Ultra 3.
And I independently came to the same solution as above.
So I can confirm that

set(ARCHS arm64 armv7k arm64_32)

(adding arm64) for WATCHOS solves that problem for me.
Then I can link from watchOS project to a small test library built with this Cmake toolkit and it runs and returns correct results on Watch Ultra 3 hw.

Can make a PR if need be.

Regarding your concerns about new CPU architecture, there is this article from July 22, 2025 from Apple:

"New 64-bit requirement for watchOS apps
Beginning April 2026, watchOS apps uploaded to App Store Connect must also include 64-bit support and be built with the watchOS 26SDK. To enable 64-bit support in your project, we recommend using the default Xcode build setting of “Standard architectures” to build a single binary with 64-bit code.
You can test ARM64 compatibility for your apps in the Xcode Simulator, and on Apple Watch Series 9 or 10, or Apple Watch Ultra 2 running watchOS 26 beta."

link: New 64-bit requirement for watchOS apps

Environment:

• Xcode 26.2, watchOS 26.2, M5 Mac, macOS Tahoe 26.2