Add support for free-threading wheels

.github/workflows/build.yml

@@ -72,6 +72,7 @@ jobs:
     - name: Build wheels
       uses: pypa/[email protected]
       env:
+        CIBW_ENABLE: cpython-freethreading
         CIBW_BUILD: "cp3*"
         CIBW_ARCHS: ${{ matrix.cibw_archs }}
         CIBW_SKIP: "*-win32 *-manylinux_i686 *-musllinux_*"

c/CMakeLists.txt

@@ -41,4 +41,5 @@ add_library(qdldlamd STATIC ${amd_src} $<TARGET_OBJECTS:qdldlobject>)
 target_include_directories(qdldlamd PRIVATE
 	                   ${CMAKE_CURRENT_SOURCE_DIR}/amd/include
 	                   ${CMAKE_CURRENT_SOURCE_DIR}/qdldl/include
+                       ${CMAKE_CURRENT_BINARY_DIR}/qdldl/include
 			    )

cpp/wrapper.cpp

@@ -123,9 +123,14 @@ PySolver::PySolver(py::object A, const bool upper=false){
 }
 
 
-
-
+// py:mod_gil_not_used() is only available on newer pybind versions, and
+// is only needed when the GIL is disabled, so hide its use unless we actually
+// need it.
+#ifdef Py_GIL_DISABLED
+PYBIND11_MODULE(qdldl, m, py::mod_gil_not_used()) {
+#else
 PYBIND11_MODULE(qdldl, m) {
+#endif
   m.doc() = "QDLDL wrapper";
   py::class_<PySolver>(m, "Solver")
 	  .def(py::init<py::object, bool>(), py::arg("A"), py::arg("upper") = false)

setup.py

@@ -98,6 +98,7 @@ def build_extensions(self):
                   sources=glob(os.path.join('cpp', '*.cpp')),
                   include_dirs=[os.path.join('c'),
                                 os.path.join('c', 'qdldl', 'include'),
+                                os.path.join(qdldl_build_dir, 'qdldl', 'include'),
                                 get_pybind_include(),
                                 get_pybind_include(user=False)],
                   language='c++',