bpo-42504: Ensure that get_config_var('MACOSX_DEPLOYMENT_TARGET') is a string (GH-24341) (GH-24410)

* bpo-42504: Ensure that get_config_var('MACOSX_DEPLOYMENT_TARGET') is a string
(cherry picked from commit 49926cf2bcc8b44d9b8f148d81979ada191dd9d5)

Co-authored-by: Ronald Oussoren <ronaldoussoren@mac.com>

6 files changed, 21 insertions, 6 deletions

diff --git a/Lib/distutils/spawn.py b/Lib/distutils/spawn.py
index f50edd2da9..0d1bd0391e 100644
--- a/Lib/distutils/spawn.py
+++ b/Lib/distutils/spawn.py
@@ -54,8 +54,8 @@ def spawn(cmd, search_path=1, verbose=0, dry_run=0):
         global _cfg_target, _cfg_target_split
         if _cfg_target is None:
             from distutils import sysconfig
-            _cfg_target = str(sysconfig.get_config_var(
-                                  'MACOSX_DEPLOYMENT_TARGET') or '')
+            _cfg_target = sysconfig.get_config_var(
+                                  'MACOSX_DEPLOYMENT_TARGET') or ''
             if _cfg_target:
                 _cfg_target_split = [int(x) for x in _cfg_target.split('.')]
         if _cfg_target:
diff --git a/Lib/distutils/tests/test_build_ext.py b/Lib/distutils/tests/test_build_ext.py
index 1b034c9302..808c0dc287 100644
--- a/Lib/distutils/tests/test_build_ext.py
+++ b/Lib/distutils/tests/test_build_ext.py
@@ -455,7 +455,7 @@ class BuildExtTestCase(TempdirManager,
         deptarget = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
         if deptarget:
             # increment the minor version number (i.e. 10.6 -> 10.7)
-            deptarget = [int(x) for x in str(deptarget).split('.')]
+            deptarget = [int(x) for x in deptarget.split('.')]
             deptarget[-1] += 1
             deptarget = '.'.join(str(i) for i in deptarget)
             self._try_compile_deployment_target('<', deptarget)
@@ -488,7 +488,7 @@ class BuildExtTestCase(TempdirManager,
 
         # get the deployment target that the interpreter was built with
         target = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
-        target = tuple(map(int, str(target).split('.')[0:2]))
+        target = tuple(map(int, target.split('.')[0:2]))
         # format the target value as defined in the Apple
         # Availability Macros.  We can't use the macro names since
         # at least one value we test with will not exist yet.
diff --git a/Lib/sysconfig.py b/Lib/sysconfig.py
index 59da8e5290..e3f79bfde5 100644
--- a/Lib/sysconfig.py
+++ b/Lib/sysconfig.py
@@ -18,6 +18,11 @@ __all__ = [
     'parse_config_h',
 ]
 
+# Keys for get_config_var() that are never converted to Python integers.
+_ALWAYS_STR = {
+    'MACOSX_DEPLOYMENT_TARGET',
+}
+
 _INSTALL_SCHEMES = {
     'posix_prefix': {
         'stdlib': '{installed_base}/{platlibdir}/python{py_version_short}',
@@ -240,6 +245,9 @@ def _parse_makefile(filename, vars=None):
                 notdone[n] = v
             else:
                 try:
+                    if n in _ALWAYS_STR:
+                        raise ValueError
+
                     v = int(v)
                 except ValueError:
                     # insert literal `$'
@@ -298,6 +306,8 @@ def _parse_makefile(filename, vars=None):
                         notdone[name] = value
                     else:
                         try:
+                            if name in _ALWAYS_STR:
+                                raise ValueError
                             value = int(value)
                         except ValueError:
                             done[name] = value.strip()
@@ -459,6 +469,8 @@ def parse_config_h(fp, vars=None):
         if m:
             n, v = m.group(1, 2)
             try:
+                if n in _ALWAYS_STR:
+                    raise ValueError
                 v = int(v)
             except ValueError:
                 pass
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index bfbcbab3b6..f4edb8bd95 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -1045,7 +1045,7 @@ class PosixTester(unittest.TestCase):
         if sys.platform == 'darwin':
             import sysconfig
             dt = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET') or '10.0'
-            if tuple(int(n) for n in str(dt).split('.')[0:2]) < (10, 6):
+            if tuple(int(n) for n in dt.split('.')[0:2]) < (10, 6):
                 raise unittest.SkipTest("getgroups(2) is broken prior to 10.6")
 
         # 'id -G' and 'os.getgroups()' should return the same
diff --git a/Misc/NEWS.d/next/macOS/2021-01-26-14-36-11.bpo-42504.ZxWt71.rst b/Misc/NEWS.d/next/macOS/2021-01-26-14-36-11.bpo-42504.ZxWt71.rst
new file mode 100644
index 0000000000..a47776effe
--- /dev/null
+++ b/Misc/NEWS.d/next/macOS/2021-01-26-14-36-11.bpo-42504.ZxWt71.rst
@@ -0,0 +1,3 @@
+Ensure that the value of
+sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET') is always a string,
+even in when the value is parsable as an integer.
diff --git a/setup.py b/setup.py
index bd5f736924..d42eb9d117 100644
--- a/setup.py
+++ b/setup.py
@@ -1013,7 +1013,7 @@ class PyBuildExt(build_ext):
             os_release = int(os.uname()[2].split('.')[0])
             dep_target = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
             if (dep_target and
-                    (tuple(int(n) for n in str(dep_target).split('.')[0:2])
+                    (tuple(int(n) for n in dep_target.split('.')[0:2])
                         < (10, 5) ) ):
                 os_release = 8
             if os_release < 9: