BLD/WHL: declare Python 3 wheels as abi3-compliant

Author: neutrinoceros

setup.py

@@ -14,10 +14,24 @@
 
 import os
 import sys
+import sysconfig
 from distutils.core import setup, Extension
 
 PYTHON_SGP4_COMPILE = os.environ.get('PYTHON_SGP4_COMPILE', '')
+
+# LIMITED_API is not compatible with free-threading (as of CPython 3.14)
+USE_PY_LIMITED_API = (
+    sys.version_info[0] == 3
+    and not sysconfig.get_config_var("Py_GIL_DISABLED")
+)
+ABI3_TARGET_VERSION = "".join(str(_) for _ in sys.version_info[:2])
+ABI3_TARGET_HEX = hex(sys.hexversion & 0xFFFF00F0)
+
 ext_modules = []
+define_macros = []
+
+if USE_PY_LIMITED_API:
+    define_macros.append(("Py_LIMITED_API", ABI3_TARGET_HEX))
 
 if sys.version_info[0] == 3 and PYTHON_SGP4_COMPILE != 'never':
 
@@ -33,6 +47,8 @@
             'extension/SGP4.cpp',
             'extension/wrapper.cpp',
         ],
+        define_macros=define_macros,
+        py_limited_api=USE_PY_LIMITED_API,
 
         # TODO: can we safely figure out how to use a pair of options
         # like these, adapted to as many platforms as possible, to use
@@ -89,4 +105,7 @@
     package_data = {'sgp4': ['SGP4-VER.TLE', 'sample*', 'tcppver.out']},
     provides = ['sgp4'],
     ext_modules = ext_modules,
+    options={
+        "bdist_wheel": {"py_limited_api": "cp%s" % ABI3_TARGET_VERSION}
+    } if USE_PY_LIMITED_API else {},
 )