BLD: for C extension builds on mac, target macOS 10.9 where possible (pandas-dev#24274)

Author: robbuckley

doc/source/whatsnew/v0.24.0.rst

@@ -1630,6 +1630,7 @@ Build Changes
 
 - Building pandas for development now requires ``cython >= 0.28.2`` (:issue:`21688`)
 - Testing pandas now requires ``hypothesis>=3.58``.  You can find `the Hypothesis docs here <https://hypothesis.readthedocs.io/en/latest/index.html>`_, and a pandas-specific introduction :ref:`in the contributing guide <using-hypothesis>`. (:issue:`22280`)
+- Building pandas on macOS now targets minimum macOS 10.9 if run on macOS 10.9 or above (:issue:`23424`)
 
 Other
 ^^^^^

setup.py

@@ -10,6 +10,8 @@
 from os.path import join as pjoin
 
 import pkg_resources
+import platform
+from distutils.sysconfig import get_config_var
 import sys
 import shutil
 from distutils.version import LooseVersion
@@ -24,6 +26,10 @@ def is_platform_windows():
     return sys.platform == 'win32' or sys.platform == 'cygwin'
 
 
+def is_platform_mac():
+    return sys.platform == 'darwin'
+
+
 min_numpy_ver = '1.12.0'
 setuptools_kwargs = {
     'install_requires': [
@@ -434,6 +440,19 @@ def get_tag(self):
     extra_compile_args = ['-Wno-unused-function']
 
 
+# For mac, ensure extensions are built for macos 10.9 when compiling on a
+# 10.9 system or above, overriding distuitls behaviour which is to target
+# the version that python was built for. This may be overridden by setting
+# MACOSX_DEPLOYMENT_TARGET before calling setup.py
+if is_platform_mac():
+    if 'MACOSX_DEPLOYMENT_TARGET' not in os.environ:
+        current_system = LooseVersion(platform.mac_ver()[0])
+        python_target = LooseVersion(
+            get_config_var('MACOSX_DEPLOYMENT_TARGET'))
+        if python_target < '10.9' and current_system >= '10.9':
+            os.environ['MACOSX_DEPLOYMENT_TARGET'] = '10.9'
+
+
 # enable coverage by building cython files by setting the environment variable
 # "PANDAS_CYTHON_COVERAGE" (with a Truthy value) or by running build_ext
 # with `--with-cython-coverage`enabled