Add a setuptools/CFFI example (#8)

* add CFFI example

* switch to a setup.cfg file

* fix MANIFEST.in

* list cffi under backends dependency-group

* modify abi3 extension test to work with cffi

* add newline

Author: ngoldbaum

pyproject.toml

@@ -5,6 +5,7 @@ backends = [
   "scikit-build-core",
   "setuptools @ git+https://github.com/ngoldbaum/setuptools@abi3.abi3t",
   "packaging @ git+https://github.com/ngoldbaum/packaging@abi3.abi3t",
+  "cffi @ git+https://github.com/ngoldbaum/cffi@abi3t.abi3",
 ]
 build-tools = [
   "cython @ git+https://github.com/cython/cython@freethreading-limited-api-preview",

setuptools/cffi/MANIFEST.in

@@ -0,0 +1,3 @@
+recursive-include src/limited *.py
+include setup.py
+include pyproject.toml

setuptools/cffi/pyproject.toml

@@ -0,0 +1,14 @@
+[build-system]
+build-backend = "setuptools.build_meta"
+requires = [
+  "setuptools@git+https://github.com/ngoldbaum/setuptools@abi3.abi3t",
+  "packaging@git+https://github.com/ngoldbaum/packaging@abi3.abi3t",
+  "cffi@git+https://github.com/ngoldbaum/cffi@abi3t.abi3",
+]
+
+[project]
+name = "limited-api"
+version = "1.2.3"
+dependencies = [
+  "cffi@git+https://github.com/ngoldbaum/cffi@abi3t.abi3",
+]

setuptools/cffi/setup.cfg

@@ -0,0 +1,2 @@
+[bdist_wheel]
+py_limited_api = cp315

setuptools/cffi/setup.py

@@ -0,0 +1,7 @@
+# CFFI doesn't support declarative setup for this
+# see https://github.com/python-cffi/cffi/issues/55
+from setuptools import setup
+
+setup(
+    cffi_modules=["src/limited/gen_limited.py:ffibuilder"],
+)

setuptools/cffi/src/limited/__init__.py

@@ -0,0 +1,3 @@
+from ._limited import lib
+
+add = lib.add

setuptools/cffi/src/limited/gen_limited.py

@@ -0,0 +1,24 @@
+from cffi import FFI
+
+ffibuilder = FFI()
+
+ffibuilder.set_source(
+    "limited._limited",
+    r"""
+    #include <stdint.h>
+
+    static int64_t add(int64_t a, int64_t b) {
+        return a + b;
+    }
+    """,
+    libraries=[],
+)
+
+ffibuilder.cdef(
+    r"""
+    int64_t add(int64_t a, int64_t b);
+    """
+)
+
+if __name__ == "__main__":
+    ffibuilder.compile(verbose=True)

tests/test_wheel.py

@@ -38,9 +38,15 @@
 
 import limited
 
-# if the build system created a package, import the actual extension
 if hasattr(limited, "__path__"):
-    from limited import limited
+    if hasattr(limited, "lib"):
+        # limited.lib is present for CFFI. We had to create a Python wrapper package
+        # because CFFI doesn't directly expose wrapped functions in the top-level
+        # namespace of an extension module
+        limited = limited._limited
+    else:
+        # if the build system created a package, import the actual extension
+        from limited import limited
 
 assert ".abi3" in Path(limited.__file__).name, (
     f"{limited.__file__} is not abi3 extension")