Support python stable ABI

Author: isuruf

CMakeLists.txt

@@ -23,6 +23,7 @@ set(CMAKE_CXX_FLAGS_DEBUG ${SYMENGINE_CXX_FLAGS_DEBUG})
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${SYMENGINE_CXX_FLAGS}")
 include_directories(${SYMENGINE_INCLUDE_DIRS})
 
+set(WITH_PY_LIMITED_API OFF CACHE STRING "Use CPython's limited API")
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_CURRENT_SOURCE_DIR}/cmake/")
 find_package(Python REQUIRED)
 find_package(Cython REQUIRED)

cmake/FindPython.cmake

@@ -38,15 +38,17 @@ message(STATUS "Python version: ${PYTHON_VERSION}")
 string(REPLACE "." "" PYTHON_VERSION_WITHOUT_DOTS ${PYTHON_VERSION})
 
 if (${CMAKE_SYSTEM_NAME} STREQUAL "Windows")
-  FIND_LIBRARY(PYTHON_LIBRARY NAMES
-        python${PYTHON_VERSION}
-        python${PYTHON_VERSION}m
-        python${PYTHON_VERSION_WITHOUT_DOTS}
-      PATHS ${PYTHON_LIB_PATH} ${PYTHON_PREFIX_PATH}/lib ${PYTHON_PREFIX_PATH}/libs
-      PATH_SUFFIXES ${CMAKE_LIBRARY_ARCHITECTURE}
-      NO_DEFAULT_PATH
-      NO_SYSTEM_ENVIRONMENT_PATH
-  )
+    if (WITH_PY_LIMITED_API)
+        set(PYTHON_LIBRARY_NAMES python3)
+    else()
+        set(PYTHON_LIBRARY_NAMES python${PYTHON_VERSION} python${PYTHON_VERSION}m python${PYTHON_VERSION_WITHOUT_DOTS})
+    endif()
+    FIND_LIBRARY(PYTHON_LIBRARY NAMES ${PYTHON_LIBRARY_NAMES}
+        PATHS ${PYTHON_LIB_PATH} ${PYTHON_PREFIX_PATH}/lib ${PYTHON_PREFIX_PATH}/libs
+        PATH_SUFFIXES ${CMAKE_LIBRARY_ARCHITECTURE}
+        NO_DEFAULT_PATH
+        NO_SYSTEM_ENVIRONMENT_PATH
+    )
 endif()
 
 execute_process(
@@ -64,6 +66,12 @@ execute_process(
 )
 string(STRIP ${PYTHON_EXTENSION_SOABI_tmp} PYTHON_EXTENSION_SOABI_tmp)
 
+if (WITH_PY_LIMITED_API)
+    if (NOT ${CMAKE_SYSTEM_NAME} STREQUAL "Windows")
+        set(PYTHON_EXTENSION_SOABI_tmp ".abi3")
+    endif()
+endif()
+
 set(PYTHON_EXTENSION_SOABI ${PYTHON_EXTENSION_SOABI_tmp}
     CACHE STRING "Suffix for python extensions")
 
@@ -130,4 +138,9 @@ macro(ADD_PYTHON_LIBRARY name)
         target_link_libraries(${name} ${PYTHON_LIBRARY})
         set_target_properties(${name} PROPERTIES SUFFIX ".pyd")
     ENDIF()
+    IF(WITH_PY_LIMITED_API)
+            target_compile_definitions(${name} PRIVATE
+            Py_LIMITED_API=${WITH_PY_LIMITED_API}
+            CYTHON_LIMITED_API=1)
+    ENDIF()
 endmacro(ADD_PYTHON_LIBRARY)

setup.py

@@ -65,6 +65,7 @@ def get_build_dir(dist):
     ('build-type=', None, 'build type: Release or Debug'),
     ('define=', 'D',
      'options to cmake <var>:<type>=<value>'),
+    ('py-limited-api=', None, 'Use Py_LIMITED_API with given version.'),
 ]
 
 def _process_define(arg):
@@ -91,6 +92,7 @@ def initialize_options(self):
         self.symengine_dir = None
         self.generator = None
         self.build_type = "Release"
+        self.py_limited_api = None
 
     def finalize_options(self):
         _build_ext.finalize_options(self)
@@ -122,6 +124,13 @@ def cmake_build(self):
         cmake_cmd.extend(process_opts(cmake_opts))
         if not path.exists(path.join(build_dir, "CMakeCache.txt")):
             cmake_cmd.extend(self.get_generator())
+
+        if self.py_limited_api:
+            assert self.py_limited_api.startswith("cp3")
+            py_ver_minor = int(self.py_limited_api[3:])
+            h = 3 * 16**6 + py_ver_minor * 16**4
+            cmake_cmd.append(f"-DWITH_PY_LIMITED_API={h}")
+
         if subprocess.call(cmake_cmd, cwd=build_dir) != 0:
             raise OSError("error calling cmake")