gh-95299: Rework test_cppext.py to not invoke setup.py directly

Lib/test/cppextdata/setup.py

@@ -1,5 +1,6 @@
 # gh-91321: Build a basic C++ test extension to check that the Python C API is
 # compatible with C++ and does not emit C++ compiler warnings.
+import os
 import sys
 from test import support
 
@@ -25,14 +26,8 @@
 
 def main():
     cppflags = list(CPPFLAGS)
-    if '-std=c++03' in sys.argv:
-        sys.argv.remove('-std=c++03')
-        std = 'c++03'
-        name = '_testcpp03ext'
-    else:
-        # Python currently targets C++11
-        std = 'c++11'
-        name = '_testcpp11ext'
+    std = os.environ["CPYTHON_TEST_CPP_STD"]
+    name = os.environ["CPYTHON_TEST_EXT_NAME"]
 
     cppflags = [*CPPFLAGS, f'-std={std}']
 

Lib/test/test_cppext.py

@@ -1,6 +1,10 @@
 # gh-91321: Build a basic C++ test extension to check that the Python C API is
 # compatible with C++ and does not emit C++ compiler warnings.
 import os.path
+try:
+    import ssl
+except ImportError:
+    ssl = None
 import sys
 import unittest
 import subprocess
@@ -11,8 +15,7 @@
 
 MS_WINDOWS = (sys.platform == 'win32')
 
-
-SETUP_TESTCPPEXT = support.findfile('setup_testcppext.py')
+PKG_CPPEXTDATA = os.path.join(os.path.dirname(__file__), "cppextdata")
 
 
 @support.requires_subprocess()
@@ -31,6 +34,8 @@ def test_build_cpp03(self):
     @unittest.skipIf(
         '-fsanitize' in (sysconfig.get_config_var('PY_CFLAGS') or ''),
         'test does not work with analyzing builds')
+    # the test uses pip which needs a TLS connection to PyPI
+    @unittest.skipIf(ssl is None, 'No ssl module')
     # the test uses venv+pip: skip if it's not available
     @support.requires_venv_with_pip()
     def check_build(self, std_cpp03, extension_name):
@@ -59,11 +64,15 @@ def _check_build(self, std_cpp03, extension_name):
             python = os.path.join(venv_dir, 'bin', python_exe)
 
         def run_cmd(operation, cmd):
+            env = os.environ.copy()
+            env['CPYTHON_TEST_CPP_STD'] = 'c++03' if std_cpp03 else 'c++11'
+            env['CPYTHON_TEST_EXT_NAME'] = extension_name
             if verbose:
                 print('Run:', ' '.join(cmd))
-                subprocess.run(cmd, check=True)
+                subprocess.run(cmd, check=True, env=env)
             else:
                 proc = subprocess.run(cmd,
+                                      env=env,
                                       stdout=subprocess.PIPE,
                                       stderr=subprocess.STDOUT,
                                       text=True)
@@ -72,16 +81,9 @@ def run_cmd(operation, cmd):
                     self.fail(
                         f"{operation} failed with exit code {proc.returncode}")
 
-        # Build the C++ extension
+        # Build and install the C++ extension
         cmd = [python, '-X', 'dev',
-               SETUP_TESTCPPEXT, 'build_ext', '--verbose']
-        if std_cpp03:
-            cmd.append('-std=c++03')
-        run_cmd('Build', cmd)
-
-        # Install the C++ extension
-        cmd = [python, '-X', 'dev',
-               SETUP_TESTCPPEXT, 'install']
+               '-m', 'pip', 'install', PKG_CPPEXTDATA]
         run_cmd('Install', cmd)
 
         # Do a reference run. Until we test that running python