# Build Error: \_ffi\_type\_longdouble symbol not found for arm64 during Python build

**URL:** <https://discourse.slicer.org/t/build-error-ffi-type-longdouble-symbol-not-found-for-arm64-during-python-build/45650>\
**Category:** Development\
**Created:** [January 1, 2026, 10:40am UTC](https://discourse.slicer.org/t/build-error-ffi-type-longdouble-symbol-not-found-for-arm64-during-python-build/45650 "2026-01-01T10:40:42Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![jamesobutler](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jamesobutler/32/7511_2.png) [@jamesobutler](https://discourse.slicer.org/u/jamesobutler)\
**Post date:** [January 1, 2026, 1:40pm UTC](https://discourse.slicer.org/t/build-error-ffi-type-longdouble-symbol-not-found-for-arm64-during-python-build/45650/2 "2026-01-01T13:40:23Z")

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Currently macOS arm64 builds are not supported. There are still some remaining items to fix as you discovered. You can however build on an Apple Silicon Mac by building the application as x86\_64 and running it using Rosetta 2.

See the following issue and other discourse thread about current state of things:

> <https://github.com/Slicer/Slicer/issues/6811>
>
> This is meta issues aiming to organize the sub-tasks associated with arm64 suppo…rt. See Sub-issues listed below.
> 
> 
> Related issues and pull requests:
> \* https://github.com/Slicer/Slicer/issues/5944
> \* https://github.com/Slicer/Slicer/issues/6705
> \* https://github.com/Slicer/Slicer/issues/6490
> \* https://github.com/Slicer/Slicer/pull/8097
> 
> Related discourse posts:
> \* https://discourse.slicer.org/t/issues-running-slicer-on-macbook-m1-max/23974/3
> \* https://discourse.slicer.org/t/slicer-quit-unexpectedly-on-macbook-with-m1-chip/25989
> \* https://discourse.slicer.org/t/build-arm-32-openssl/31204
> \* https://discourse.slicer.org/t/developing-for-slicer-on-apple-silicon-build-targeting-x86-64/40686

> [@Build 3D Slicer for MacOS arm64?](https://discourse.slicer.org/t/build-3d-slicer-for-macos-arm64/35699):
>
> PyTorch has support for using the shaders in the M series chips, but to use it, one has to use the arm64 version of Python. Should a native (in this case, M3) build of Slicer3D be possible? If yes, where should I get the 5.15.2 Qt package (for MacOS arm64)? Thank you! Gene

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