Try to build with stable API

Author: jschueller

.github/workflows/build.yml

@@ -62,16 +62,15 @@ jobs:
         with:
           submodules: true
 
-      - name: Setup Python 3.11
+      - name: Setup Python 3.6
         uses: actions/setup-python@v2
         with:
-          python-version: '3.11'
+          python-version: '3.6'
 
       - name: Build wheels
         env:
-          # only build CPython-3.8 and later and skip 32-bit builds and skip windows
-          # CIBW_BUILD: cp38-* cp39-* cp310-* cp311-*
-          CIBW_BUILD: cp311-*
+          # only build CPython-3.6+ and skip 32-bit builds and skip windows
+          CIBW_BUILD: cp36-*
           CIBW_SKIP: "*-win* *-manylinux_i686 *-musllinux*"
           # use latest build
           CIBW_MANYLINUX_X86_64_IMAGE: quay.io/pypa/manylinux2014_x86_64

extensions.py

@@ -57,6 +57,12 @@ def build_extension(self, ext: Extension):
             ext.source_dir.as_posix()
         ]
 
+        if platform.system() == "Windows":
+            cmd += "-DPYTHON_EXTENSION_MODULE_SUFFIX=.abi3.so"
+        else:
+            cmd += "-DPYTHON_EXTENSION_MODULE_SUFFIX=.abi3.pyd"
+        abi3_flag = "-DPy_LIMITED_API=0x03060000"
+
         if platform.system() == "Windows":
             cmd.insert(2, f"-DCMAKE_LIBRARY_OUTPUT_DIRECTORY_{self.config.upper()}={_ed}")
 
@@ -65,7 +71,7 @@ def build_extension(self, ext: Extension):
             cwd=build_dir,
             env={
                 **os.environ.copy(),
-                "CXXFLAGS": f'{os.environ.get("CXXFLAGS", "")} -DVERSION_INFO="{self.distribution.get_version()}"'
+                "CXXFLAGS": f'{os.environ.get("CXXFLAGS", "")} -DVERSION_INFO="{self.distribution.get_version()}" {abi3_flag}'
             })
 
         # build the DLL

setup.py

@@ -5,6 +5,8 @@
 
 from extensions import NLOptBuild, NLOptBuildExtension
 
+from wheel.bdist_wheel import bdist_wheel
+
 with open("README.md") as f:
     long_description = f.read()
 
@@ -16,10 +18,23 @@
         version.append(m.group(1))
     version = ".".join(version)
 
+
+class bdist_wheel_abi3(bdist_wheel):
+    def get_tag(self):
+        python, abi, plat = super().get_tag()
+
+        if python.startswith("cp"):
+            # on CPython, our wheels are abi3 and compatible back to 3.6
+            return "cp36", "abi3", plat
+
+        return python, abi, plat
+
+
 setup(
     version=version,
     install_requires=["numpy >=1.18.5"],
     ext_modules=[NLOptBuildExtension("nlopt._nlopt", version)],
-    cmdclass={"build_ext": NLOptBuild},
+    cmdclass={"build_ext": NLOptBuild,
+              "bdist_wheel": bdist_wheel_abi3},
     zip_safe=False,
 )