Issue #9516: avoid errors in sysconfig when MACOSX_DEPLOYMENT_TARGET is set in shell.

Without this patch python will fail to start properly when the environment
variable MACOSX_DEPLOYMENT_TARGET is set on MacOSX and has a value that is
not compatible with the value during Python's build. This is caused by code
in sysconfig that was only meant to be used in disutils.

sysconfig.py

@@ -428,7 +428,7 @@ def _init_posix():
         cur_target = os.getenv('MACOSX_DEPLOYMENT_TARGET', '')
         if cur_target == '':
             cur_target = cfg_target
-            os.putenv('MACOSX_DEPLOYMENT_TARGET', cfg_target)
+            os.environ['MACOSX_DEPLOYMENT_TARGET'] = cfg_target
         elif [int(x) for x in cfg_target.split('.')] > [int(x) for x in cur_target.split('.')]:
             my_msg = ('$MACOSX_DEPLOYMENT_TARGET mismatch: now "%s" but "%s" during configure'
                 % (cur_target, cfg_target))

tests/test_build_ext.py

@@ -2,6 +2,7 @@ import sys
 import os
 import shutil
 from io import StringIO
+import textwrap
 
 from distutils.core import Distribution
 from distutils.command.build_ext import build_ext
@@ -419,6 +420,67 @@ class BuildExtTestCase(TempdirManager,
         wanted = os.path.join(curdir, 'twisted', 'runner', 'portmap' + ext)
         self.assertEqual(wanted, path)
 
+
+    @unittest.skipUnless(sys.platform == 'darwin', 'test only relevant for MacOSX')
+    def test_deployment_target(self):
+        self._try_compile_deployment_target()
+
+        orig_environ = os.environ
+        os.environ = orig_environ.copy()
+        self.addCleanup(setattr, os, 'environ', orig_environ)
+
+        os.environ['MACOSX_DEPLOYMENT_TARGET']='10.1'
+        self._try_compile_deployment_target()
+
+
+    def _try_compile_deployment_target(self):
+        deptarget_c = os.path.join(self.tmp_dir, 'deptargetmodule.c')
+
+        with open(deptarget_c, 'w') as fp:
+            fp.write(textwrap.dedent('''\
+                #include <AvailabilityMacros.h>
+
+                int dummy;
+
+                #if TARGET != MAC_OS_X_VERSION_MIN_REQUIRED
+                #error "Unexpected target"
+                #endif
+
+            '''))
+
+        target = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
+        target = tuple(map(int, target.split('.')))
+        target = '%02d%01d0' % target
+
+        deptarget_ext = Extension(
+            'deptarget',
+            [deptarget_c],
+            extra_compile_args=['-DTARGET=%s'%(target,)],
+        )
+        dist = Distribution({
+            'name': 'deptarget',
+            'ext_modules': [deptarget_ext]
+        })
+        dist.package_dir = self.tmp_dir
+        cmd = build_ext(dist)
+        cmd.build_lib = self.tmp_dir
+        cmd.build_temp = self.tmp_dir
+
+        try:
+            old_stdout = sys.stdout
+            if not support.verbose:
+                # silence compiler output
+                sys.stdout = StringIO()
+            try:
+                cmd.ensure_finalized()
+                cmd.run()
+            finally:
+                sys.stdout = old_stdout
+
+        except CompileError:
+            self.fail("Wrong deployment target during compilation")
+
+
 def test_suite():
     src = _get_source_filename()
     if not os.path.exists(src):

tests/test_util.py

@@ -92,7 +92,7 @@ class UtilTestCase(support.EnvironGuard, unittest.TestCase):
                    ('Darwin Kernel Version 8.11.1: '
                     'Wed Oct 10 18:23:28 PDT 2007; '
                     'root:xnu-792.25.20~1/RELEASE_I386'), 'i386'))
-        os.environ['MACOSX_DEPLOYMENT_TARGET'] = '10.3'
+        get_config_vars()['MACOSX_DEPLOYMENT_TARGET'] = '10.3'
 
         get_config_vars()['CFLAGS'] = ('-fno-strict-aliasing -DNDEBUG -g '
                                        '-fwrapv -O3 -Wall -Wstrict-prototypes')
@@ -105,7 +105,7 @@ class UtilTestCase(support.EnvironGuard, unittest.TestCase):
             sys.maxsize = cursize
 
         # macbook with fat binaries (fat, universal or fat64)
-        os.environ['MACOSX_DEPLOYMENT_TARGET'] = '10.4'
+        get_config_vars()['MACOSX_DEPLOYMENT_TARGET'] = '10.4'
         get_config_vars()['CFLAGS'] = ('-arch ppc -arch i386 -isysroot '
                                        '/Developer/SDKs/MacOSX10.4u.sdk  '
                                        '-fno-strict-aliasing -fno-common '
@@ -113,6 +113,10 @@ class UtilTestCase(support.EnvironGuard, unittest.TestCase):
 
         self.assertEqual(get_platform(), 'macosx-10.4-fat')
 
+        os.environ['MACOSX_DEPLOYMENT_TARGET'] = '10.1'
+        self.assertEqual(get_platform(), 'macosx-10.4-fat')
+
+
         get_config_vars()['CFLAGS'] = ('-arch x86_64 -arch i386 -isysroot '
                                        '/Developer/SDKs/MacOSX10.4u.sdk  '
                                        '-fno-strict-aliasing -fno-common '
@@ -147,6 +151,7 @@ class UtilTestCase(support.EnvironGuard, unittest.TestCase):
 
             self.assertEqual(get_platform(), 'macosx-10.4-%s'%(arch,))
 
+
         # linux debian sarge
         os.name = 'posix'
         sys.version = ('2.3.5 (#1, Jul  4 2007, 17:28:59) '

util.py

@@ -96,9 +96,7 @@ def get_platform ():
         from distutils.sysconfig import get_config_vars
         cfgvars = get_config_vars()
 
-        macver = os.environ.get('MACOSX_DEPLOYMENT_TARGET')
-        if not macver:
-            macver = cfgvars.get('MACOSX_DEPLOYMENT_TARGET')
+        macver = cfgvars.get('MACOSX_DEPLOYMENT_TARGET')
 
         if 1:
             # Always calculate the release of the running machine,