CI: Add Cygwin CMake run

.github/workflows/run_tests_win_cygwin.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: windows-latest
     defaults:
       run:
-        shell: bash -eo pipefail -o igncr "{0}"
+        shell: C:/cygwin/bin/bash.exe -eo pipefail -o igncr "{0}"
 
     name: Cygwin-based Autotools tests
 
@@ -27,18 +27,20 @@ jobs:
 
     steps:
       - name: Fix line endings
+        shell: pwsh
         run: git config --global core.autocrlf input
 
       - uses: actions/checkout@v4
 
-      - uses: cygwin/cygwin-install-action@v2
+      - uses: cygwin/cygwin-install-action@v4
         with:
           platform: x86_64
+          install-dir: 'C:\cygwin'
           packages: >-
             git automake libtool autoconf2.5 make libhdf5-devel
             libhdf4-devel zipinfo libxml2-devel perl zlib-devel
             libzstd-devel libbz2-devel libaec-devel libzip-devel
-            libdeflate-devel gcc-core libcurl-devel libiconv-devel
+            libdeflate-devel gcc-core gcc-g++ libcurl-devel libiconv-devel
             libssl-devel libcrypt-devel
 
       - name: (Autotools) Run autoconf and friends
@@ -80,3 +82,72 @@ jobs:
         timeout-minutes: 30
         run: |
           make check -j8 SHELL=/bin/dash
+  
+  build-and-test-cmake:
+    name: Cygwin-based CMake tests
+    runs-on: windows-latest
+    defaults:
+      run:
+        shell: C:/cygwin/bin/bash.exe -eo pipefail -o igncr "{0}"
+
+    steps:
+
+      - run: git config --global core.autocrlf input
+        shell: pwsh
+      - uses: actions/checkout@v4
+      - uses: cygwin/cygwin-install-action@v4
+        with:
+          platform: x86_64
+          install-dir: 'C:\cygwin'
+          packages: >-
+            git automake libtool autoconf2.5 make libhdf5-devel
+            libhdf4-devel zipinfo libxml2-devel perl zlib-devel
+            libzstd-devel libbz2-devel libaec-devel libzip-devel
+            libdeflate-devel gcc-core gcc-g++ libcurl-devel libiconv-devel
+            libssl-devel libcrypt-devel cmake ninja make m4 diffutils unzip
+
+###
+# Configure and build
+###
+
+      - name: (CMake) Configure Build
+        env:
+          MAKE: "/usr/bin/make"
+          CXX: "/usr/bin/g++"
+        run: |
+          /usr/bin/cmake \
+          -G"Unix Makefiles" \
+          -B build \
+          -S . \
+          -DCMAKE_INSTALL_PREFIX=/tmp \
+          -DBUILD_SHARED_LIBS=ON \
+          -DNETCDF_ENABLE_NETCDF_4=ON \
+          -DNETCDF_BUILD_UTILITIES=ON \
+          -DNETCDF_ENABLE_TESTS=ON \
+          -DNETCDF_ENABLE_HDF5=ON \
+          -DNETCDF_ENABLE_NCZARR=TRUE \
+          -DNETCDF_ENABLE_PLUGINS=ON
+        if: ${{ success() }}
+
+      - name: (CMake) Look at CMakeCache.txt if error
+        run: cat build/CMakeCache.txt
+        if: ${{ failure() }}
+
+      - name: (CMake) Print Summary
+        run: cat build/libnetcdf.settings
+
+      - name: (CMake) Build All
+        env:
+          MAKE: "/usr/bin/make"
+          CXX: "/usr/bin/g++"
+        run: cmake --build build -j$(nproc)
+        if: ${{ success() }}
+
+      - name: (CMake) Run Tests
+        run: PATH=$PWD/build:$PATH ctest --test-dir build
+        if: ${{ success() }}
+
+      - name: (CMake) Verbose output of CTest failures
+        run: >-
+          PATH=$PWD/build:$PATH ctest --test-dir build --output-on-failure -j$(nproc) --rerun-failed -VV
+        if: ${{ failure() }}

nc_test4/CMakeLists.txt

@@ -49,7 +49,7 @@ IF(USE_HDF5 AND NETCDF_ENABLE_FILTER_TESTING)
   build_bin_test(test_filter_order)
   build_bin_test(test_filter_repeat)
   build_bin_test(tst_filter_vlen)
-  if(NOT MINGW)
+  if(NOT MINGW AND NOT CYGWIN)
     ADD_SH_TEST(nc_test4 tst_filter)
   endif()
   ADD_SH_TEST(nc_test4 tst_specific_filters)

plugins/CMakeLists.txt

@@ -8,7 +8,10 @@ set(CMAKE_BUILD_TYPE "")
 
 if(WIN32)
   set(PLUGINEXT "dll")
-  set(PLUGINPRE "__nc") 
+  set(PLUGINPRE "__nc")
+elseif(CYGWIN)
+  set(PLUGINEXT "dll")
+  set(PLUGINPRE "lib__nc")
 else()
    set(PLUGINPRE "lib__nc")
    if(APPLE)