Add windows arm64 compilation

.github/workflows/build-wheels.yaml

@@ -1,5 +1,4 @@
 name: Build wheels
-
 # TODO: move into the release-deploy workflow and only run on published releases
 # on:
 #   release:
@@ -38,21 +37,8 @@ jobs:
             cibw_archs: "aarch64"
           - os: windows-2025
             cibw_archs: "AMD64"
-          # # Not happy at the moment hence turned off
-          # # It doesn't seem too far away, but something isn't quite right.
-          # # Latest run by Zeb: https://github.com/openscm/example-fgen-basic/actions/runs/17173313157/job/48725872212
-          # # Can't find numpy definitions for some reason.
-          # # Maybe helpful issue: https://github.com/numpy/numpy/issues/25000
-          # # numpy uses different compilers, might be something to try, see:
-          # # - https://github.com/numpy/numpy/actions/runs/17087345049/job/48453931521
-          # # - https://github.com/numpy/numpy/blob/37c9cb68ba7db9c48bc0e3354953c57a78d2b0e8/.github/workflows/wheels.yml#L129
-          # # scipy doesn't bother building windows arm wheels, see:
-          # # - https://pypi.org/project/scipy/#files
-          # # potentially relevant scipy issues:
-          # # - https://github.com/scipy/scipy/issues/21716
-          # # - https://github.com/scipy/scipy/issues/14812
-          # - os: windows-11-arm
-          #   cibw_archs: "ARM64"
+          - os: windows-11-arm
+            cibw_archs: "ARM64"
           - os: macos-13
             cibw_archs: "x86_64"
           - os: macos-14
@@ -69,32 +55,19 @@ jobs:
           # TODO: figure out whether we need/want to use other compilers too
           compiler: "gcc"
           version: "13"
-      - name: Specify MSVC toolchain - windows-arm
-        # When building on windows ARM, we need to use the MSVC toolchain
-        # # Original from: https://github.com/matplotlib/matplotlib/blob/1ddb1eccac8cfc25dee47bc538dc5913384b253f/.github/workflows/cibuildwheel.yml#L108
-        # # On Windows, we explicitly request MSVC compilers (as GitHub Action runners have
-        # # MinGW on PATH that would be picked otherwise), switch to a static build for
-        # # runtimes, but use dynamic linking for `VCRUNTIME140.dll`, `VCRUNTIME140_1.dll`,
-        # # and the UCRT. This avoids requiring specific versions of `MSVCP140.dll`, while
-        # # keeping shared state with the rest of the Python process/extensions.
-        # CIBW_CONFIG_SETTINGS_WINDOWS: >-
-        #   setup-args="--vsenv"
-        #   setup-args="-Db_vscrt=mt"
-        #   setup-args="-Dcpp_link_args=['ucrt.lib','vcruntime.lib','/nodefaultlib:libucrt.lib','/nodefaultlib:libvcruntime.lib']"
-        run: |
-          echo 'CIBW_CONFIG_SETTINGS_WINDOWS=setup-args="--vsenv" setup-args="-Db_vscrt=mt"' >> $GITHUB_ENV
-        # TODO: figure out escaping and add back in (?)
-        # setup-args="-Dcpp_link_args=['ucrt.lib','vcruntime.lib','/nodefaultlib:libucrt.lib','/nodefaultlib:libvcruntime.lib']"
-      - name: Install Fortran compiler - windows-arm
-        # When building on windows ARM, we need to use the MSVC toolchain
+      - name: Specify LLVM - windows-arm
         if: ${{ matrix.os == 'windows-11-arm' }}
-        uses: fortran-lang/setup-fortran@v1
-        id: setup-fortran-windows-arm
-        with:
-          # Only intel-classic supported by f2py
-          # (https://numpy.org/devdocs/f2py/windows/intel.html#f2py-and-windows-intel-fortran)
-          compiler: "intel-classic"
-          version: "2021.10"
+        shell: pwsh
+        run: |
+          Invoke-WebRequest https://github.com/llvm/llvm-project/releases/download/llvmorg-20.1.8/LLVM-20.1.8-woa64.exe -OutFile LLVM-woa64.exe
+          Start-Process -FilePath ".\LLVM-woa64.exe" -ArgumentList "/S" -Wait
+
+          $env:PATH = "C:\Program Files\LLVM\bin;" + $env:PATH
+          echo "C:\Program Files\LLVM\bin" | Out-File -FilePath $env:GITHUB_PATH -Encoding utf8 -Append
+          echo "CC=clang-cl"  | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
+          echo "CXX=clang-cl" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
+          echo "FC=flang-new" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
+          echo "AR=llvm-lib.exe" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
       - name: Build wheels
         uses: pypa/cibuildwheel@v3.1.4  # matplotlib had v3.1.3
         with:

meson.build

@@ -68,17 +68,17 @@ if pyprojectwheelbuild_enabled
     'src/example_fgen_basic/runtime_helpers.py',
   )
 
-  # The ancillary library,
-  # i.e. all the stuff for wrapping that isn't directly exposed to Python.
-  ancillary_lib = library(
-    '@0@-ancillary'.format(meson.project_name()),
-    sources: srcs_ancillary_lib,
-    version: meson.project_version(),
-    dependencies: [],
-    # any other dependencies which aren't in source e.g. fgen-core
-    # e.g. dependencies: [fgen_core_dep],
-    install: false,
-  )
+    # The ancillary library,
+    # i.e. all the stuff for wrapping that isn't directly exposed to Python.
+   ancillary_lib = library(
+      '@0@-ancillary'.format(meson.project_name()),
+      sources: srcs_ancillary_lib,
+      version: meson.project_version(),
+      dependencies: [],
+      # any other dependencies which aren't in source e.g. fgen-core
+      # e.g. dependencies: [fgen_core_dep],
+      install: false,
+      )
 
   ancillary_dep = declare_dependency(link_with: ancillary_lib)