# Error building FFTW on Windows

**URL:** https://discourse.julialang.org/t/error-building-fftw-on-windows/125025
**Category:** General Usage
**Tags:** question, package, fftw
**Created:** [January 21, 2025, 3:38pm UTC](https://discourse.julialang.org/t/error-building-fftw-on-windows/125025 "2025-01-21T15:38:36Z")
**Posts on this page:** 8
**Page:** 1

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### Author: ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)
#### Post date: [January 21, 2025, 3:38pm UTC](https://discourse.julialang.org/t/error-building-fftw-on-windows/125025/1 "2025-01-21T15:38:36Z")

</div>

Any idea:

> <https://github.com/aenarete/KiteControllers.jl/actions/runs/12889591653/job/35937174830>

```julia
ERROR: LoadError: Unable to open libLLVM!
...
 in expression starting at C:\Users\runneradmin\.julia\packages\FFTW\oepdx\deps\build_fftw.jl:1
in expression starting at C:\Users\runneradmin\.julia\packages\FFTW\oepdx\deps\build.jl:20
ERROR: LoadError: Error building `FFTW`: 

```

This happens only on Windows, and it worked last week.

What could be the reason?

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### Author: ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)
#### Post date: [January 21, 2025, 7:41pm UTC](https://discourse.julialang.org/t/error-building-fftw-on-windows/125025/2 "2025-01-21T19:41:21Z")

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> [@Precompilation errors while adding self-developed package to another package](https://discourse.julialang.org/t/precompilation-errors-while-adding-self-developed-package-to-another-package/124028/3):
>
> My educated guess: you’re using Julia v1.10 or older. And the package manager for some reason decided to favour an incredibly old version of FFMPEG.jl which required the super old package BinaryProvider.jl (when resolving an environment there are often several possible solutions and one has to be picked based on some heuristics, but these heuristics aren’t infallibile). One workaround is to add FFMPEG@0.4 to your environment. Another option is to use Julia v1.11, which doesn’t allow installing B…

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### Author: ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)
#### Post date: [January 21, 2025, 10:59pm UTC](https://discourse.julialang.org/t/error-building-fftw-on-windows/125025/4 "2025-01-21T22:59:10Z")

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@ufechner7 instead of [adding FFTW](https://github.com/aenarete/KiteControllers.jl/commit/ddc7c67074a9d67b8fe4a0030d3f8fcbe77cbfe0) which you don’t directly use, why don’t you upgrade DSP.jl to v0.8 in

> <https://github.com/ufechner7/KiteModels.jl/blob/59d7ec29152166fac0fc3d0670cfc7c66d7a994a/Project.toml#L45>

which would automatically require a much newer FFTW for you

> <https://github.com/JuliaDSP/DSP.jl/blob/v0.8.0/Project.toml#L25>

?

On an unrelated (?) note, you may want to reactivate CompatHelper in [your](https://github.com/ufechner7/KiteModels.jl/actions/workflows/CompatHelper.yml) [repositories](https://github.com/aenarete/KiteControllers.jl/actions/workflows/CompatHelper.yml)

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<div class="post-metadata">

### Author: ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)
#### Post date: [January 22, 2025, 9:33am UTC](https://discourse.julialang.org/t/error-building-fftw-on-windows/125025/5 "2025-01-22T09:33:31Z")

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> [@giordano](#):
>
> why don’t you upgrade [DSP.jl](https://juliaregistries.github.io/General/packages/redirect_to_repo/DSP) to v0.8 in

Because my code does not work with DSP 0.8.

My software depends on about 500 packages. If I would always upgrade all dependencies to the newest (braking) version I would not have much time left to do anything else.

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<div class="post-metadata">

### Author: ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)
#### Post date: [January 22, 2025, 9:35am UTC](https://discourse.julialang.org/t/error-building-fftw-on-windows/125025/6 "2025-01-22T09:35:52Z")

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I added:

```julia
[deps]
FFTW = "7a1cc6ca-52ef-59f5-83cd-3a7055c09341"
[compat]
FFTW = "1.8.0"

```

to Project.toml, and now it works.

Thank you!

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<div class="post-metadata">

### Author: ![JoshuaLampert](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/joshualampert/32/205964_2.png) [@JoshuaLampert](https://discourse.julialang.org/u/JoshuaLampert)
#### Post date: [January 22, 2025, 10:07am UTC](https://discourse.julialang.org/t/error-building-fftw-on-windows/125025/7 "2025-01-22T10:07:16Z")

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I think the true fix would be merging [allow MKL\_jll version 2025 by ranocha · Pull Request #314 · JuliaMath/FFTW.jl · GitHub](https://github.com/JuliaMath/FFTW.jl/pull/314) and registering a new version of FFTW.jl including this fix.

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<div class="post-metadata">

### Author: ![JoshuaLampert](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/joshualampert/32/205964_2.png) [@JoshuaLampert](https://discourse.julialang.org/u/JoshuaLampert)
#### Post date: [January 22, 2025, 8:17pm UTC](https://discourse.julialang.org/t/error-building-fftw-on-windows/125025/8 "2025-01-22T20:17:59Z")

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With [allow MKL\_jll version 2025 by ranocha · Pull Request #314 · JuliaMath/FFTW.jl · GitHub](https://github.com/JuliaMath/FFTW.jl/pull/314) being merged and FFTW.jl v1.8.1 being released, you should be able to remove the dependency of FFTW.jl in your package again, @ufechner7.

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<div class="post-metadata">

### Author: ![ufechner7](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ufechner7/32/51363_2.png) [@ufechner7](https://discourse.julialang.org/u/ufechner7)
#### Post date: [January 22, 2025, 8:46pm UTC](https://discourse.julialang.org/t/error-building-fftw-on-windows/125025/9 "2025-01-22T20:46:20Z")

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Thank you!