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diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index d14793a..65aa3ad 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -728,6 +728,45 @@ conflict.
.. versionadded:: 3.6
+
+.. envvar:: PYTHONCOERCECLOCALE
+
+ 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.
+
+ 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
+ ``C`` locale, then the Python CLI will attempt to configure one of the
+ following locales for the given locale categories before loading the
+ interpreter runtime:
+
+ * ``C.UTF-8`` (``LC_ALL``)
+ * ``C.utf8`` (``LC_ALL``)
+ * ``UTF-8`` (``LC_CTYPE``)
+
+ If setting one of these locale categories succeeds, then the matching
+ environment variables will be set (both ``LC_ALL`` and ``LANG`` for the
+ ``LC_ALL`` category, and ``LC_CTYPE`` for the ``LC_CTYPE`` category) in
+ the current process environment before the Python runtime is initialized.
+
+ Configuring one of these locales (either explicitly or via the above
+ implicit locale coercion) will automatically set the error handler for
+ :data:`sys.stdin` and :data:`sys.stdout` to ``surrogateescape``. This
+ behavior can be overridden using :envvar:`PYTHONIOENCODING` as usual.
+
+ For debugging purposes, setting ``PYTHONCOERCECLOCALE=warn`` will cause
+ Python to emit warning messages on ``stderr`` if either the locale coercion
+ activates, or else if a locale that *would* have triggered coercion is
+ still active when the Python runtime is initialized.
+
+ Availability: \*nix
+
+ .. versionadded:: 3.7
+ See :pep:`538` for more details.
+
Debug-mode variables
~~~~~~~~~~~~~~~~~~~~
diff --git a/Lib/test/support/script_helper.py b/Lib/test/support/script_helper.py
index 507dc48..c3cb720 100644
--- a/Lib/test/support/script_helper.py
+++ b/Lib/test/support/script_helper.py
@@ -56,8 +56,35 @@ def interpreter_requires_environment():
return __cached_interp_requires_environment
-_PythonRunResult = collections.namedtuple("_PythonRunResult",
- ("rc", "out", "err"))
+class _PythonRunResult(collections.namedtuple("_PythonRunResult",
+ ("rc", "out", "err"))):
+ """Helper for reporting Python subprocess run results"""
+ def fail(self, cmd_line):
+ """Provide helpful details about failed subcommand runs"""
+ # Limit to 80 lines to ASCII characters
+ maxlen = 80 * 100
+ out, err = self.out, self.err
+ if len(out) > maxlen:
+ out = b'(... truncated stdout ...)' + out[-maxlen:]
+ if len(err) > maxlen:
+ err = b'(... truncated stderr ...)' + err[-maxlen:]
+ out = out.decode('ascii', 'replace').rstrip()
+ err = err.decode('ascii', 'replace').rstrip()
+ raise AssertionError("Process return code is %d\n"
+ "command line: %r\n"
+ "\n"
+ "stdout:\n"
+ "---\n"
+ "%s\n"
+ "---\n"
+ "\n"
+ "stderr:\n"
+ "---\n"
+ "%s\n"
+ "---"
+ % (self.rc, cmd_line,
+ out,
+ err))
# Executing the interpreter in a subprocess
@@ -115,30 +142,7 @@ def run_python_until_end(*args, **env_vars):
def _assert_python(expected_success, *args, **env_vars):
res, cmd_line = run_python_until_end(*args, **env_vars)
if (res.rc and expected_success) or (not res.rc and not expected_success):
- # Limit to 80 lines to ASCII characters
- maxlen = 80 * 100
- out, err = res.out, res.err
- if len(out) > maxlen:
- out = b'(... truncated stdout ...)' + out[-maxlen:]
- if len(err) > maxlen:
- err = b'(... truncated stderr ...)' + err[-maxlen:]
- out = out.decode('ascii', 'replace').rstrip()
- err = err.decode('ascii', 'replace').rstrip()
- raise AssertionError("Process return code is %d\n"
- "command line: %r\n"
- "\n"
- "stdout:\n"
- "---\n"
- "%s\n"
- "---\n"
- "\n"
- "stderr:\n"
- "---\n"
- "%s\n"
- "---"
- % (res.rc, cmd_line,
- out,
- err))
+ res.fail(cmd_line)
return res
def assert_python_ok(*args, **env_vars):
diff --git a/Lib/test/test_c_locale_coercion.py b/Lib/test/test_c_locale_coercion.py
new file mode 100644
index 0000000..635c98f
--- /dev/null
+++ b/Lib/test/test_c_locale_coercion.py
@@ -0,0 +1,371 @@
+# Tests the attempted automatic coercion of the C locale to a UTF-8 locale
+
+import unittest
+import locale
+import os
+import sys
+import sysconfig
+import shutil
+import subprocess
+from collections import namedtuple
+
+import test.support
+from test.support.script_helper import (
+ run_python_until_end,
+ interpreter_requires_environment,
+)
+
+# Set our expectation for the default encoding used in the C locale
+# for the filesystem encoding and the standard streams
+
+# AIX uses iso8859-1 in the C locale, other *nix platforms use ASCII
+if sys.platform.startswith("aix"):
+ C_LOCALE_STREAM_ENCODING = "iso8859-1"
+else:
+ C_LOCALE_STREAM_ENCODING = "ascii"
+
+# FS encoding is UTF-8 on macOS, other *nix platforms use the locale encoding
+if sys.platform == "darwin":
+ C_LOCALE_FS_ENCODING = "utf-8"
+else:
+ C_LOCALE_FS_ENCODING = C_LOCALE_STREAM_ENCODING
+
+# Note that the above is probably still wrong in some cases, such as:
+# * Windows when PYTHONLEGACYWINDOWSFSENCODING is set
+# * AIX and any other platforms that use latin-1 in the C locale
+#
+# Options for dealing with this:
+# * Don't set PYTHON_COERCE_C_LOCALE on such platforms (e.g. Windows doesn't)
+# * Fix the test expectations to match the actual platform behaviour
+
+# In order to get the warning messages to match up as expected, the candidate
+# order here must much the target locale order in Python/pylifecycle.c
+_C_UTF8_LOCALES = ("C.UTF-8", "C.utf8", "UTF-8")
+
+# There's no reliable cross-platform way of checking locale alias
+# lists, so the only way of knowing which of these locales will work
+# is to try them with locale.setlocale(). We do that in a subprocess
+# to avoid altering the locale of the test runner.
+#
+# If the relevant locale module attributes exist, and we're not on a platform
+# where we expect it to always succeed, we also check that
+# `locale.nl_langinfo(locale.CODESET)` works, as if it fails, the interpreter
+# will skip locale coercion for that particular target locale
+_check_nl_langinfo_CODESET = bool(
+ sys.platform not in ("darwin", "linux") and
+ hasattr(locale, "nl_langinfo") and
+ hasattr(locale, "CODESET")
+)
+
+def _set_locale_in_subprocess(locale_name):
+ cmd_fmt = "import locale; print(locale.setlocale(locale.LC_CTYPE, '{}'))"
+ if _check_nl_langinfo_CODESET:
+ # 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)
+ return result.rc == 0
+
+
+
+_fields = "fsencoding stdin_info stdout_info stderr_info lang lc_ctype lc_all"
+_EncodingDetails = namedtuple("EncodingDetails", _fields)
+
+class EncodingDetails(_EncodingDetails):
+ # XXX (ncoghlan): Using JSON for child state reporting may be less fragile
+ CHILD_PROCESS_SCRIPT = ";".join([
+ "import sys, os",
+ "print(sys.getfilesystemencoding())",
+ "print(sys.stdin.encoding + ':' + sys.stdin.errors)",
+ "print(sys.stdout.encoding + ':' + sys.stdout.errors)",
+ "print(sys.stderr.encoding + ':' + sys.stderr.errors)",
+ "print(os.environ.get('LANG', 'not set'))",
+ "print(os.environ.get('LC_CTYPE', 'not set'))",
+ "print(os.environ.get('LC_ALL', 'not set'))",
+ ])
+
+ @classmethod
+ def get_expected_details(cls, coercion_expected, fs_encoding, stream_encoding, env_vars):
+ """Returns expected child process details for a given encoding"""
+ _stream = stream_encoding + ":{}"
+ # stdin and stdout should use surrogateescape either because the
+ # coercion triggered, or because the C locale was detected
+ stream_info = 2*[_stream.format("surrogateescape")]
+ # stderr should always use backslashreplace
+ stream_info.append(_stream.format("backslashreplace"))
+ expected_lang = env_vars.get("LANG", "not set").lower()
+ if coercion_expected:
+ expected_lc_ctype = CLI_COERCION_TARGET.lower()
+ else:
+ expected_lc_ctype = env_vars.get("LC_CTYPE", "not set").lower()
+ expected_lc_all = env_vars.get("LC_ALL", "not set").lower()
+ env_info = expected_lang, expected_lc_ctype, expected_lc_all
+ return dict(cls(fs_encoding, *stream_info, *env_info)._asdict())
+
+ @staticmethod
+ def _handle_output_variations(data):
+ """Adjust the output to handle platform specific idiosyncrasies
+
+ * Some platforms report ASCII as ANSI_X3.4-1968
+ * Some platforms report ASCII as US-ASCII
+ * Some platforms report UTF-8 instead of utf-8
+ """
+ data = data.replace(b"ANSI_X3.4-1968", b"ascii")
+ data = data.replace(b"US-ASCII", b"ascii")
+ data = data.lower()
+ return data
+
+ @classmethod
+ def get_child_details(cls, env_vars):
+ """Retrieves fsencoding and standard stream details from a child process
+
+ Returns (encoding_details, stderr_lines):
+
+ - encoding_details: EncodingDetails for eager decoding
+ - stderr_lines: result of calling splitlines() on the stderr output
+
+ The child is run in isolated mode if the current interpreter supports
+ that.
+ """
+ result, py_cmd = run_python_until_end(
+ "-c", cls.CHILD_PROCESS_SCRIPT,
+ __isolated=True,
+ **env_vars
+ )
+ if not result.rc == 0:
+ result.fail(py_cmd)
+ # All subprocess outputs in this test case should be pure ASCII
+ adjusted_output = cls._handle_output_variations(result.out)
+ stdout_lines = adjusted_output.decode("ascii").splitlines()
+ child_encoding_details = dict(cls(*stdout_lines)._asdict())
+ stderr_lines = result.err.decode("ascii").rstrip().splitlines()
+ return child_encoding_details, stderr_lines
+
+
+# Details of the shared library warning emitted at runtime
+LEGACY_LOCALE_WARNING = (
+ "Python runtime initialized with LC_CTYPE=C (a locale with default ASCII "
+ "encoding), which may cause Unicode compatibility problems. Using C.UTF-8, "
+ "C.utf8, or UTF-8 (if available) as alternative Unicode-compatible "
+ "locales is recommended."
+)
+
+# Details of the CLI locale coercion warning emitted at runtime
+CLI_COERCION_WARNING_FMT = (
+ "Python detected LC_CTYPE=C: LC_CTYPE coerced to {} (set another locale "
+ "or PYTHONCOERCECLOCALE=0 to disable this locale coercion behavior)."
+)
+
+
+AVAILABLE_TARGETS = None
+CLI_COERCION_TARGET = None
+CLI_COERCION_WARNING = None
+
+def setUpModule():
+ global AVAILABLE_TARGETS
+ global CLI_COERCION_TARGET
+ global CLI_COERCION_WARNING
+
+ if AVAILABLE_TARGETS is not None:
+ # initialization already done
+ return
+ AVAILABLE_TARGETS = []
+
+ # Find the target locales available in the current system
+ for target_locale in _C_UTF8_LOCALES:
+ if _set_locale_in_subprocess(target_locale):
+ AVAILABLE_TARGETS.append(target_locale)
+
+ if AVAILABLE_TARGETS:
+ # Coercion is expected to use the first available target locale
+ CLI_COERCION_TARGET = AVAILABLE_TARGETS[0]
+ CLI_COERCION_WARNING = CLI_COERCION_WARNING_FMT.format(CLI_COERCION_TARGET)
+
+
+class _LocaleHandlingTestCase(unittest.TestCase):
+ # Base class to check expected locale handling behaviour
+
+ def _check_child_encoding_details(self,
+ env_vars,
+ expected_fs_encoding,
+ expected_stream_encoding,
+ expected_warnings,
+ coercion_expected):
+ """Check the C locale handling for the given process environment
+
+ Parameters:
+ expected_fs_encoding: expected sys.getfilesystemencoding() result
+ expected_stream_encoding: expected encoding for standard streams
+ expected_warning: stderr output to expect (if any)
+ """
+ result = EncodingDetails.get_child_details(env_vars)
+ encoding_details, stderr_lines = result
+ expected_details = EncodingDetails.get_expected_details(
+ coercion_expected,
+ expected_fs_encoding,
+ expected_stream_encoding,
+ env_vars
+ )
+ self.assertEqual(encoding_details, expected_details)
+ if expected_warnings is None:
+ expected_warnings = []
+ self.assertEqual(stderr_lines, expected_warnings)
+
+
+class LocaleConfigurationTests(_LocaleHandlingTestCase):
+ # Test explicit external configuration via the process environment
+
+ def setUpClass():
+ # This relies on setupModule() having been run, so it can't be
+ # handled via the @unittest.skipUnless decorator
+ if not AVAILABLE_TARGETS:
+ raise unittest.SkipTest("No C-with-UTF-8 locale available")
+
+ def test_external_target_locale_configuration(self):
+
+ # Explicitly setting a target locale should give the same behaviour as
+ # is seen when implicitly coercing to that target locale
+ self.maxDiff = None
+
+ expected_fs_encoding = "utf-8"
+ expected_stream_encoding = "utf-8"
+
+ base_var_dict = {
+ "LANG": "",
+ "LC_CTYPE": "",
+ "LC_ALL": "",
+ }
+ for env_var in ("LANG", "LC_CTYPE"):
+ for locale_to_set in AVAILABLE_TARGETS:
+ # XXX (ncoghlan): LANG=UTF-8 doesn't appear to work as
+ # expected, so skip that combination for now
+ # See https://bugs.python.org/issue30672 for discussion
+ if env_var == "LANG" and locale_to_set == "UTF-8":
+ continue
+
+ with self.subTest(env_var=env_var,
+ configured_locale=locale_to_set):
+ var_dict = base_var_dict.copy()
+ var_dict[env_var] = locale_to_set
+ self._check_child_encoding_details(var_dict,
+ expected_fs_encoding,
+ expected_stream_encoding,
+ expected_warnings=None,
+ coercion_expected=False)
+
+
+
+@test.support.cpython_only
+@unittest.skipUnless(sysconfig.get_config_var("PY_COERCE_C_LOCALE"),
+ "C locale coercion disabled at build time")
+class LocaleCoercionTests(_LocaleHandlingTestCase):
+ # Test implicit reconfiguration of the environment during CLI startup
+
+ def _check_c_locale_coercion(self,
+ fs_encoding, stream_encoding,
+ coerce_c_locale,
+ expected_warnings=None,
+ coercion_expected=True,
+ **extra_vars):
+ """Check the C locale handling for various configurations
+
+ Parameters:
+ fs_encoding: expected sys.getfilesystemencoding() result
+ stream_encoding: expected encoding for standard streams
+ coerce_c_locale: setting to use for PYTHONCOERCECLOCALE
+ None: don't set the variable at all
+ str: the value set in the child's environment
+ expected_warnings: expected warning lines on stderr
+ extra_vars: additional environment variables to set in subprocess
+ """
+ self.maxDiff = None
+
+ if not AVAILABLE_TARGETS:
+ # Locale coercion is disabled when there aren't any target locales
+ fs_encoding = C_LOCALE_FS_ENCODING
+ stream_encoding = C_LOCALE_STREAM_ENCODING
+ coercion_expected = False
+ if expected_warnings:
+ expected_warnings = [LEGACY_LOCALE_WARNING]
+
+ base_var_dict = {
+ "LANG": "",
+ "LC_CTYPE": "",
+ "LC_ALL": "",
+ }
+ base_var_dict.update(extra_vars)
+ for env_var in ("LANG", "LC_CTYPE"):
+ for locale_to_set in ("", "C", "POSIX", "invalid.ascii"):
+ # XXX (ncoghlan): *BSD platforms don't behave as expected in the
+ # POSIX locale, so we skip that for now
+ # See https://bugs.python.org/issue30672 for discussion
+ if locale_to_set == "POSIX":
+ continue
+ with self.subTest(env_var=env_var,
+ nominal_locale=locale_to_set,
+ PYTHONCOERCECLOCALE=coerce_c_locale):
+ var_dict = base_var_dict.copy()
+ var_dict[env_var] = locale_to_set
+ if coerce_c_locale is not None:
+ var_dict["PYTHONCOERCECLOCALE"] = coerce_c_locale
+ # Check behaviour on successful coercion
+ self._check_child_encoding_details(var_dict,
+ fs_encoding,
+ stream_encoding,
+ expected_warnings,
+ coercion_expected)
+
+ def test_test_PYTHONCOERCECLOCALE_not_set(self):
+ # This should coerce to the first available target locale by default
+ self._check_c_locale_coercion("utf-8", "utf-8", coerce_c_locale=None)
+
+ def test_PYTHONCOERCECLOCALE_not_zero(self):
+ # *Any* string other than "0" is considered "set" for our purposes
+ # and hence should result in the locale coercion being enabled
+ for setting in ("", "1", "true", "false"):
+ self._check_c_locale_coercion("utf-8", "utf-8", coerce_c_locale=setting)
+
+ def test_PYTHONCOERCECLOCALE_set_to_warn(self):
+ # PYTHONCOERCECLOCALE=warn enables runtime warnings for legacy locales
+ self._check_c_locale_coercion("utf-8", "utf-8",
+ coerce_c_locale="warn",
+ expected_warnings=[CLI_COERCION_WARNING])
+
+
+ def test_PYTHONCOERCECLOCALE_set_to_zero(self):
+ # The setting "0" should result in the locale coercion being disabled
+ self._check_c_locale_coercion(C_LOCALE_FS_ENCODING,
+ C_LOCALE_STREAM_ENCODING,
+ coerce_c_locale="0",
+ coercion_expected=False)
+ # Setting LC_ALL=C shouldn't make any difference to the behaviour
+ self._check_c_locale_coercion(C_LOCALE_FS_ENCODING,
+ C_LOCALE_STREAM_ENCODING,
+ coerce_c_locale="0",
+ LC_ALL="C",
+ coercion_expected=False)
+
+ def test_LC_ALL_set_to_C(self):
+ # Setting LC_ALL should render the locale coercion ineffective
+ self._check_c_locale_coercion(C_LOCALE_FS_ENCODING,
+ C_LOCALE_STREAM_ENCODING,
+ coerce_c_locale=None,
+ LC_ALL="C",
+ coercion_expected=False)
+ # And result in a warning about a lack of locale compatibility
+ self._check_c_locale_coercion(C_LOCALE_FS_ENCODING,
+ C_LOCALE_STREAM_ENCODING,
+ coerce_c_locale="warn",
+ LC_ALL="C",
+ expected_warnings=[LEGACY_LOCALE_WARNING],
+ coercion_expected=False)
+
+def test_main():
+ test.support.run_unittest(
+ LocaleConfigurationTests,
+ LocaleCoercionTests
+ )
+ test.support.reap_children()
+
+if __name__ == "__main__":
+ test_main()
diff --git a/Lib/test/test_cmd_line.py b/Lib/test/test_cmd_line.py
index 38156b4..5922ed9 100644
--- a/Lib/test/test_cmd_line.py
+++ b/Lib/test/test_cmd_line.py
@@ -153,6 +153,7 @@ class CmdLineTest(unittest.TestCase):
env = os.environ.copy()
# Use C locale to get ascii for the locale encoding
env['LC_ALL'] = 'C'
+ env['PYTHONCOERCECLOCALE'] = '0'
code = (
b'import locale; '
b'print(ascii("' + undecodable + b'"), '
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 7866a5c..b41239a 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -680,6 +680,7 @@ class SysModuleTest(unittest.TestCase):
# Force the POSIX locale
env = os.environ.copy()
env["LC_ALL"] = "C"
+ env["PYTHONCOERCECLOCALE"] = "0"
code = '\n'.join((
'import sys',
'def dump(name):',
diff --git a/Modules/main.c b/Modules/main.c
index 585d696..96d8be4 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -107,7 +107,11 @@ static const char usage_6[] =
" predictable seed.\n"
"PYTHONMALLOC: set the Python memory allocators and/or install debug hooks\n"
" on Python memory allocators. Use PYTHONMALLOC=debug to install debug\n"
-" hooks.\n";
+" hooks.\n"
+
+"PYTHONCOERCECLOCALE: if this variable is set to 0, it disables the locale\n"
+" coercion behavior. Use PYTHONCOERCECLOCALE=warn to request display of\n"
+" locale coercion and locale compatibility warnings on stderr.\n";
static int
usage(int exitcode, const wchar_t* program)
diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index 813cf30..2a64092 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -1,4 +1,5 @@
#include <Python.h>
+#include "pyconfig.h"
#include "pythread.h"
#include <stdio.h>
diff --git a/Programs/python.c b/Programs/python.c
index a7afbc7..03f8295 100644
--- a/Programs/python.c
+++ b/Programs/python.c
@@ -15,6 +15,21 @@ wmain(int argc, wchar_t **argv)
}
#else
+/* Access private pylifecycle helper API to better handle the legacy C locale
+ *
+ * The legacy C locale assumes ASCII as the default text encoding, which
+ * causes problems not only for the CPython runtime, but also other
+ * components like GNU readline.
+ *
+ * Accordingly, when the CLI detects it, it attempts to coerce it to a
+ * more capable UTF-8 based alternative.
+ *
+ * See the documentation of the PYTHONCOERCECLOCALE setting for more details.
+ *
+ */
+extern int _Py_LegacyLocaleDetected(void);
+extern void _Py_CoerceLegacyLocale(void);
+
int
main(int argc, char **argv)
{
@@ -25,7 +40,11 @@ main(int argc, char **argv)
char *oldloc;
/* Force malloc() allocator to bootstrap Python */
+#ifdef Py_DEBUG
+ (void)_PyMem_SetupAllocators("malloc_debug");
+# else
(void)_PyMem_SetupAllocators("malloc");
+# endif
argv_copy = (wchar_t **)PyMem_RawMalloc(sizeof(wchar_t*) * (argc+1));
argv_copy2 = (wchar_t **)PyMem_RawMalloc(sizeof(wchar_t*) * (argc+1));
@@ -49,7 +68,21 @@ main(int argc, char **argv)
return 1;
}
+#ifdef __ANDROID__
+ /* Passing "" to setlocale() on Android requests the C locale rather
+ * than checking environment variables, so request C.UTF-8 explicitly
+ */
+ setlocale(LC_ALL, "C.UTF-8");
+#else
+ /* Reconfigure the locale to the default for this process */
setlocale(LC_ALL, "");
+#endif
+
+ if (_Py_LegacyLocaleDetected()) {
+ _Py_CoerceLegacyLocale();
+ }
+
+ /* Convert from char to wchar_t based on the locale settings */
for (i = 0; i < argc; i++) {
argv_copy[i] = Py_DecodeLocale(argv[i], NULL);
if (!argv_copy[i]) {
@@ -70,7 +103,11 @@ main(int argc, char **argv)
/* Force again malloc() allocator to release memory blocks allocated
before Py_Main() */
+#ifdef Py_DEBUG
+ (void)_PyMem_SetupAllocators("malloc_debug");
+# else
(void)_PyMem_SetupAllocators("malloc");
+# endif
for (i = 0; i < argc; i++) {
PyMem_RawFree(argv_copy2[i]);
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index ecfdfee..4fee178 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -167,6 +167,7 @@ Py_SetStandardStreamEncoding(const char *encoding, const char *errors)
return 0;
}
+
/* Global initializations. Can be undone by Py_FinalizeEx(). Don't
call this twice without an intervening Py_FinalizeEx() call. When
initializations fail, a fatal error is issued and the function does
@@ -301,6 +302,183 @@ import_init(PyInterpreterState *interp, PyObject *sysmod)
}
+/* Helper functions to better handle the legacy C locale
+ *
+ * The legacy C locale assumes ASCII as the default text encoding, which
+ * causes problems not only for the CPython runtime, but also other
+ * components like GNU readline.
+ *
+ * Accordingly, when the CLI detects it, it attempts to coerce it to a
+ * more capable UTF-8 based alternative as follows:
+ *
+ * if (_Py_LegacyLocaleDetected()) {
+ * _Py_CoerceLegacyLocale();
+ * }
+ *
+ * See the documentation of the PYTHONCOERCECLOCALE setting for more details.
+ *
+ * Locale coercion also impacts the default error handler for the standard
+ * streams: while the usual default is "strict", the default for the legacy
+ * C locale and for any of the coercion target locales is "surrogateescape".
+ */
+
+int
+_Py_LegacyLocaleDetected(void)
+{
+#ifndef MS_WINDOWS
+ /* On non-Windows systems, the C locale is considered a legacy locale */
+ /* XXX (ncoghlan): some platforms (notably Mac OS X) don't appear to treat
+ * the POSIX locale as a simple alias for the C locale, so
+ * we may also want to check for that explicitly.
+ */
+ const char *ctype_loc = setlocale(LC_CTYPE, NULL);
+ return ctype_loc != NULL && strcmp(ctype_loc, "C") == 0;
+#else
+ /* Windows uses code pages instead of locales, so no locale is legacy */
+ return 0;
+#endif
+}
+
+
+static const char *_C_LOCALE_WARNING =
+ "Python runtime initialized with LC_CTYPE=C (a locale with default ASCII "
+ "encoding), which may cause Unicode compatibility problems. Using C.UTF-8, "
+ "C.utf8, or UTF-8 (if available) as alternative Unicode-compatible "
+ "locales is recommended.\n";
+
+static int
+_legacy_locale_warnings_enabled(void)
+{
+ const char *coerce_c_locale = getenv("PYTHONCOERCECLOCALE");
+ return (coerce_c_locale != NULL &&
+ strncmp(coerce_c_locale, "warn", 5) == 0);
+}
+
+static void
+_emit_stderr_warning_for_legacy_locale(void)
+{
+ if (_legacy_locale_warnings_enabled()) {
+ if (_Py_LegacyLocaleDetected()) {
+ fprintf(stderr, "%s", _C_LOCALE_WARNING);
+ }
+ }
+}
+
+typedef struct _CandidateLocale {
+ const char *locale_name; /* The locale to try as a coercion target */
+} _LocaleCoercionTarget;
+
+static _LocaleCoercionTarget _TARGET_LOCALES[] = {
+ {"C.UTF-8"},
+ {"C.utf8"},
+ {"UTF-8"},
+ {NULL}
+};
+
+static char *
+get_default_standard_stream_error_handler(void)
+{
+ const char *ctype_loc = setlocale(LC_CTYPE, NULL);
+ if (ctype_loc != NULL) {
+ /* "surrogateescape" is the default in the legacy C locale */
+ if (strcmp(ctype_loc, "C") == 0) {
+ return "surrogateescape";
+ }
+
+#ifdef PY_COERCE_C_LOCALE
+ /* "surrogateescape" is the default in locale coercion target locales */
+ const _LocaleCoercionTarget *target = NULL;
+ for (target = _TARGET_LOCALES; target->locale_name; target++) {
+ if (strcmp(ctype_loc, target->locale_name) == 0) {
+ return "surrogateescape";
+ }
+ }
+#endif
+ }
+
+ /* Otherwise return NULL to request the typical default error handler */
+ return NULL;
+}
+
+#ifdef PY_COERCE_C_LOCALE
+static const char *_C_LOCALE_COERCION_WARNING =
+ "Python detected LC_CTYPE=C: LC_CTYPE coerced to %.20s (set another locale "
+ "or PYTHONCOERCECLOCALE=0 to disable this locale coercion behavior).\n";
+
+static void
+_coerce_default_locale_settings(const _LocaleCoercionTarget *target)
+{
+
+ const char *newloc = target->locale_name;
+
+ /* Reset locale back to currently configured defaults */
+ setlocale(LC_ALL, "");
+
+ /* Set the relevant locale environment variable */
+ if (setenv("LC_CTYPE", newloc, 1)) {
+ fprintf(stderr,
+ "Error setting LC_CTYPE, skipping C locale coercion\n");
+ return;
+ }
+ if (_legacy_locale_warnings_enabled()) {
+ fprintf(stderr, _C_LOCALE_COERCION_WARNING, newloc);
+ }
+
+ /* Reconfigure with the overridden environment variables */
+ setlocale(LC_ALL, "");
+}
+#endif
+
+
+void
+_Py_CoerceLegacyLocale(void)
+{
+#ifdef PY_COERCE_C_LOCALE
+ /* We ignore the Python -E and -I flags here, as the CLI needs to sort out
+ * the locale settings *before* we try to do anything with the command
+ * line arguments. For cross-platform debugging purposes, we also need
+ * to give end users a way to force even scripts that are otherwise
+ * isolated from their environment to use the legacy ASCII-centric C
+ * locale.
+ *
+ * Ignoring -E and -I is safe from a security perspective, as we only use
+ * the setting to turn *off* the implicit locale coercion, and anyone with
+ * access to the process environment already has the ability to set
+ * `LC_ALL=C` to override the C level locale settings anyway.
+ */
+ const char *coerce_c_locale = getenv("PYTHONCOERCECLOCALE");
+ if (coerce_c_locale == NULL || strncmp(coerce_c_locale, "0", 2) != 0) {
+ /* PYTHONCOERCECLOCALE is not set, or is set to something other than "0" */
+ const char *locale_override = getenv("LC_ALL");
+ if (locale_override == NULL || *locale_override == '\0') {
+ /* LC_ALL is also not set (or is set to an empty string) */
+ const _LocaleCoercionTarget *target = NULL;
+ for (target = _TARGET_LOCALES; target->locale_name; target++) {
+ const char *new_locale = setlocale(LC_CTYPE,
+ target->locale_name);
+ if (new_locale != NULL) {
+#if !defined(__APPLE__) && defined(HAVE_LANGINFO_H) && defined(CODESET)
+ /* Also ensure that nl_langinfo works in this locale */
+ char *codeset = nl_langinfo(CODESET);
+ if (!codeset || *codeset == '\0') {
+ /* CODESET is not set or empty, so skip coercion */
+ new_locale = NULL;
+ setlocale(LC_CTYPE, "");
+ continue;
+ }
+#endif
+ /* Successfully configured locale, so make it the default */
+ _coerce_default_locale_settings(target);
+ return;
+ }
+ }
+ }
+ }
+ /* No C locale warning here, as Py_Initialize will emit one later */
+#endif
+}
+
+
void
_Py_InitializeEx_Private(int install_sigs, int install_importlib)
{
@@ -315,11 +493,19 @@ _Py_InitializeEx_Private(int install_sigs, int install_importlib)
initialized = 1;
_Py_Finalizing = NULL;
-#ifdef HAVE_SETLOCALE
+#ifdef __ANDROID__
+ /* Passing "" to setlocale() on Android requests the C locale rather
+ * than checking environment variables, so request C.UTF-8 explicitly
+ */
+ setlocale(LC_CTYPE, "C.UTF-8");
+#else
+#ifndef MS_WINDOWS
/* Set up the LC_CTYPE locale, so we can obtain
the locale's charset without having to switch
locales. */
setlocale(LC_CTYPE, "");
+ _emit_stderr_warning_for_legacy_locale();
+#endif
#endif
if ((p = Py_GETENV("PYTHONDEBUG")) && *p != '\0')
@@ -1247,12 +1433,8 @@ initstdio(void)
}
}
if (!errors && !(pythonioencoding && *pythonioencoding)) {
- /* When the LC_CTYPE locale is the POSIX locale ("C locale"),
- stdin and stdout use the surrogateescape error handler by
- default, instead of the strict error handler. */
- char *loc = setlocale(LC_CTYPE, NULL);
- if (loc != NULL && strcmp(loc, "C") == 0)
- errors = "surrogateescape";
+ /* Choose the default error handler based on the current locale */
+ errors = get_default_standard_stream_error_handler();
}
}
diff --git a/configure.ac b/configure.ac
index 3f2459a..7444486 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3360,6 +3360,40 @@ then
fi
AC_MSG_RESULT($with_pymalloc)
+# Check for --with-c-locale-coercion
+AC_MSG_CHECKING(for --with-c-locale-coercion)
+AC_ARG_WITH(c-locale-coercion,
+ AS_HELP_STRING([--with(out)-c-locale-coercion],
+ [disable/enable C locale coercion to a UTF-8 based locale]))
+
+if test -z "$with_c_locale_coercion"
+then
+ with_c_locale_coercion="yes"
+fi
+if test "$with_c_locale_coercion" != "no"
+then
+ AC_DEFINE(PY_COERCE_C_LOCALE, 1,
+ [Define if you want to coerce the C locale to a UTF-8 based locale])
+fi
+AC_MSG_RESULT($with_c_locale_coercion)
+
+# Check for --with-c-locale-warning
+AC_MSG_CHECKING(for --with-c-locale-warning)
+AC_ARG_WITH(c-locale-warning,
+ AS_HELP_STRING([--with(out)-c-locale-warning],
+ [disable/enable locale compatibility warning in the C locale]))
+
+if test -z "$with_c_locale_warning"
+then
+ with_c_locale_warning="yes"
+fi
+if test "$with_c_locale_warning" != "no"
+then
+ AC_DEFINE(PY_WARN_ON_C_LOCALE, 1,
+ [Define to emit a locale compatibility warning in the C locale])
+fi
+AC_MSG_RESULT($with_c_locale_warning)
+
# Check for Valgrind support
AC_MSG_CHECKING([for --with-valgrind])
AC_ARG_WITH([valgrind],
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