Fix build warning

Author: Huelse

README.md

@@ -1,11 +1,11 @@
 ## Microsoft SEAL For Python
 
+This is a python binding for the Microsoft SEAL library.
+
 Microsoft [**SEAL**](https://github.com/microsoft/SEAL) is an easy-to-use open-source ([MIT licensed](https://github.com/microsoft/SEAL/blob/master/LICENSE)) homomorphic encryption library developed by the Cryptography Research group at Microsoft.
 
 [**pybind11**](https://github.com/pybind/pybind11) is a lightweight header-only library that exposes C++ types in Python and vice versa, mainly to create Python bindings of existing C++ code.
 
-This is a python binding for the Microsoft SEAL library.
-
 [![Supported Versions](https://img.shields.io/pypi/pyversions/SEAL-Python.svg)](https://github.com/Huelse/SEAL-Python)
 
 
@@ -35,6 +35,16 @@ python -m pip install seal-python
 
 ## Build
 
+On macOS, use the same deployment target for both the SEAL static library and the Python extension to avoid linker warnings about mismatched macOS versions:
+
+```shell
+export MACOSX_DEPLOYMENT_TARGET=$(python3 - <<'PY'
+import sysconfig
+print(sysconfig.get_config_var("MACOSX_DEPLOYMENT_TARGET") or "15.0")
+PY
+)
+```
+
 * ### Linux
 
   Recommend: Clang++ (>= 10.0) or GNU G++ (>= 9.4), CMake (>= 3.16)
@@ -58,6 +68,8 @@ python -m pip install seal-python
   # Build the SEAL lib without the msgsl zlib and zstandard compression
   cd SEAL
   cmake -S . -B build -DSEAL_USE_MSGSL=OFF -DSEAL_USE_ZLIB=OFF -DSEAL_USE_ZSTD=OFF
+  # macOS:
+  cmake -S . -B build -DSEAL_USE_MSGSL=OFF -DSEAL_USE_ZLIB=OFF -DSEAL_USE_ZSTD=OFF -DCMAKE_OSX_DEPLOYMENT_TARGET=${MACOSX_DEPLOYMENT_TARGET}
   cmake --build build
   cd ..
 

setup.py

@@ -4,6 +4,7 @@
 from pathlib import Path
 from shutil import copy2
 import sys
+import sysconfig
 from setuptools import setup
 from distutils.sysconfig import get_python_inc
 import pybind11
@@ -24,6 +25,17 @@
     extra_objects = sorted(glob('SEAL/build/lib/*.a'))
 
 cpp_args = ['/std:c++17', '/utf-8', '/bigobj'] if platform.system() == "Windows" else ['-std=c++17']
+link_args = []
+
+if platform.system() == "Darwin":
+    deployment_target = os.environ.get("MACOSX_DEPLOYMENT_TARGET") or sysconfig.get_config_var(
+        "MACOSX_DEPLOYMENT_TARGET"
+    )
+    if deployment_target:
+        deployment_flag = f"-mmacosx-version-min={deployment_target}"
+        os.environ.setdefault("MACOSX_DEPLOYMENT_TARGET", deployment_target)
+        cpp_args.append(deployment_flag)
+        link_args.append(deployment_flag)
 
 if len(extra_objects) < 1 or not os.path.exists(extra_objects[0]):
     print('Not found the seal lib file, check the "SEAL/build/lib"')
@@ -60,6 +72,7 @@ def _copy_typing_files(self):
         sorted(glob('src/*.cpp')),
         include_dirs=include_dirs,
         extra_compile_args=cpp_args,
+        extra_link_args=link_args,
         extra_objects=extra_objects,
         define_macros=[('VERSION_INFO', __version__)],
     ),
@@ -83,7 +96,6 @@ def _copy_typing_files(self):
         "Development Status :: 4 - Beta",
         "Intended Audience :: Developers",
         "Intended Audience :: Science/Research",
-        "License :: OSI Approved :: MIT License",
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3 :: Only",
         "Programming Language :: Python :: 3.8",