bpo-29240, bpo-32030: Py_Main() re-reads config if encoding changes

Doc/using/cmdline.rst

@@ -779,9 +779,7 @@ conflict.
 
    If set to the value ``0``, causes the main Python command line application
    to skip coercing the legacy ASCII-based C locale to a more capable UTF-8
-   based alternative. Note that this setting is checked even when the
-   :option:`-E` or :option:`-I` options are used, as it is handled prior to
-   the processing of command line options.
+   based alternative.
 
    If this variable is *not* set, or is set to a value other than ``0``, and
    the current locale reported for the ``LC_CTYPE`` category is the default

Include/pylifecycle.h

@@ -105,6 +105,9 @@ PyAPI_FUNC(int) Py_FdIsInteractive(FILE *, const char *);
 
 /* Bootstrap __main__ (defined in Modules/main.c) */
 PyAPI_FUNC(int) Py_Main(int argc, wchar_t **argv);
+#ifdef Py_BUILD_CORE
+PyAPI_FUNC(int) _Py_UnixMain(int argc, char **argv);
+#endif
 
 /* In getpath.c */
 PyAPI_FUNC(wchar_t *) Py_GetProgramFullPath(void);
@@ -194,7 +197,7 @@ PyAPI_FUNC(int) _PyOS_URandomNonblock(void *buffer, Py_ssize_t size);
 
 /* Legacy locale support */
 #ifndef Py_LIMITED_API
-PyAPI_FUNC(void) _Py_CoerceLegacyLocale(void);
+PyAPI_FUNC(void) _Py_CoerceLegacyLocale(const _PyCoreConfig *config);
 PyAPI_FUNC(int) _Py_LegacyLocaleDetected(void);
 PyAPI_FUNC(char *) _Py_SetLocaleFromEnv(int category);
 #endif

Include/pystate.h

@@ -38,15 +38,19 @@ typedef struct {
     int show_alloc_count;   /* -X showalloccount */
     int dump_refs;          /* PYTHONDUMPREFS */
     int malloc_stats;       /* PYTHONMALLOCSTATS */
-    int utf8_mode;          /* -X utf8 or PYTHONUTF8 environment variable */
+    int coerce_c_locale;    /* PYTHONCOERCECLOCALE, -1 means unknown */
+    int coerce_c_locale_warn; /* PYTHONCOERCECLOCALE=warn */
+    int utf8_mode;          /* -X utf8 or PYTHONUTF8 environment variable,
+                               -1 means unknown */
 
     wchar_t *module_search_path_env; /* PYTHONPATH environment variable */
     wchar_t *home;          /* PYTHONHOME environment variable,
                                see also Py_SetPythonHome(). */
     wchar_t *program_name;  /* Program name, see also Py_GetProgramName() */
 } _PyCoreConfig;
 
-#define _PyCoreConfig_INIT (_PyCoreConfig){.use_hash_seed = -1}
+#define _PyCoreConfig_INIT \
+    (_PyCoreConfig){.use_hash_seed = -1, .coerce_c_locale = -1, .utf8_mode = -1}
 /* Note: _PyCoreConfig_INIT sets other fields to 0/NULL */
 
 /* Placeholders while working on the new configuration API

Lib/test/test_c_locale_coercion.py

@@ -65,7 +65,7 @@ def _set_locale_in_subprocess(locale_name):
         # If there's no valid CODESET, we expect coercion to be skipped
         cmd_fmt += "; import sys; sys.exit(not locale.nl_langinfo(locale.CODESET))"
     cmd = cmd_fmt.format(locale_name)
-    result, py_cmd = run_python_until_end("-c", cmd, __isolated=True)
+    result, py_cmd = run_python_until_end("-c", cmd, PYTHONCOERCECLOCALE='')
     return result.rc == 0
 
 
@@ -131,7 +131,6 @@ def get_child_details(cls, env_vars):
         """
         result, py_cmd = run_python_until_end(
             "-X", "utf8=0", "-c", cls.CHILD_PROCESS_SCRIPT,
-            __isolated=True,
             **env_vars
         )
         if not result.rc == 0:
@@ -236,6 +235,7 @@ def test_external_target_locale_configuration(self):
             "LANG": "",
             "LC_CTYPE": "",
             "LC_ALL": "",
+            "PYTHONCOERCECLOCALE": "",
         }
         for env_var in ("LANG", "LC_CTYPE"):
             for locale_to_set in AVAILABLE_TARGETS:
@@ -294,6 +294,7 @@ def _check_c_locale_coercion(self,
             "LANG": "",
             "LC_CTYPE": "",
             "LC_ALL": "",
+            "PYTHONCOERCECLOCALE": "",
         }
         base_var_dict.update(extra_vars)
         for env_var in ("LANG", "LC_CTYPE"):

Lib/test/test_cmd_line.py

@@ -551,7 +551,7 @@ def test_xdev(self):
         self.assertEqual(out, "True")
 
         # Warnings
-        code = ("import sys, warnings; "
+        code = ("import warnings; "
                 "print(' '.join('%s::%s' % (f[0], f[2].__name__) "
                                 "for f in warnings.filters))")
         if Py_DEBUG:

Lib/test/test_utf8_mode.py

@@ -7,16 +7,19 @@
 import sys
 import textwrap
 import unittest
+from test import support
 from test.support.script_helper import assert_python_ok, assert_python_failure
 
 
 MS_WINDOWS = (sys.platform == 'win32')
 
 
 class UTF8ModeTests(unittest.TestCase):
-    # Override PYTHONUTF8 and PYTHONLEGACYWINDOWSFSENCODING environment
-    # variables by default
-    DEFAULT_ENV = {'PYTHONUTF8': '', 'PYTHONLEGACYWINDOWSFSENCODING': ''}
+    DEFAULT_ENV = {
+        'PYTHONUTF8': '',
+        'PYTHONLEGACYWINDOWSFSENCODING': '',
+        'PYTHONCOERCECLOCALE': '0',
+    }
 
     def posix_locale(self):
         loc = locale.setlocale(locale.LC_CTYPE, None)
@@ -53,7 +56,7 @@ def test_xoption(self):
         self.assertEqual(out, '0')
 
         if MS_WINDOWS:
-            # PYTHONLEGACYWINDOWSFSENCODING disables the UTF-8
+            # PYTHONLEGACYWINDOWSFSENCODING disables the UTF-8 Mode
             # and has the priority over -X utf8
             out = self.get_output('-X', 'utf8', '-c', code,
                                   PYTHONLEGACYWINDOWSFSENCODING='1')
@@ -201,6 +204,25 @@ def test_locale_getpreferredencoding(self):
         out = self.get_output('-X', 'utf8', '-c', code, LC_ALL='C')
         self.assertEqual(out, 'UTF-8 UTF-8')
 
+    @unittest.skipIf(MS_WINDOWS, 'test specific to Unix')
+    def test_cmd_line(self):
+        arg = 'h\xe9\u20ac'.encode('utf-8')
+        arg_utf8 = arg.decode('utf-8')
+        arg_ascii = arg.decode('ascii', 'surrogateescape')
+        code = 'import locale, sys; print("%s:%s" % (locale.getpreferredencoding(), ascii(sys.argv[1:])))'
+
+        def check(utf8_opt, expected, **kw):
+            out = self.get_output('-X', utf8_opt, '-c', code, arg, **kw)
+            args = out.partition(':')[2].rstrip()
+            self.assertEqual(args, ascii(expected), out)
+
+        check('utf8', [arg_utf8])
+        if sys.platform == 'darwin' or support.is_android:
+            c_arg = arg_utf8
+        else:
+            c_arg = arg_ascii
+        check('utf8=0', [c_arg], LC_ALL='C')
+
 
 if __name__ == "__main__":
     unittest.main()

Modules/getpath.c

@@ -112,7 +112,7 @@ extern "C" {
 
 #define DECODE_LOCALE_ERR(NAME, LEN) \
     ((LEN) == (size_t)-2) \
-     ? _Py_INIT_USER_ERR("cannot decode " #NAME) \
+     ? _Py_INIT_USER_ERR("cannot decode " NAME) \
      : _Py_INIT_NO_MEMORY()
 
 typedef struct {