gh-126742: Add _PyErr_SetLocaleString, use it for gdbm & dlerror messages (GH-126746)

- Add a helper to set an error from locale-encoded `char*`
- Use the helper for gdbm & dlerror messages

Co-authored-by: Victor Stinner <vstinner@python.org>

2 files changed, 86 insertions, 15 deletions

diff --git a/Lib/test/test_ctypes/test_dlerror.py b/Lib/test/test_ctypes/test_dlerror.py
index 4441e30..c3c34d4 100644
--- a/Lib/test/test_ctypes/test_dlerror.py
+++ b/Lib/test/test_ctypes/test_dlerror.py
@@ -1,7 +1,12 @@
+import _ctypes
 import os
+import platform
 import sys
+import test.support
 import unittest
-import platform
+from ctypes import CDLL, c_int
+from ctypes.util import find_library
+
 
 FOO_C = r"""
 #include <unistd.h>
@@ -26,7 +31,7 @@ void *foo(void)
 
 
 @unittest.skipUnless(sys.platform.startswith('linux'),
-                     'Test only valid for Linux')
+                     'test requires GNU IFUNC support')
 class TestNullDlsym(unittest.TestCase):
     """GH-126554: Ensure that we catch NULL dlsym return values
 
@@ -53,14 +58,6 @@ class TestNullDlsym(unittest.TestCase):
         import subprocess
         import tempfile
 
-        # To avoid ImportErrors on Windows, where _ctypes does not have
-        # dlopen and dlsym,
-        # import here, i.e., inside the test function.
-        # The skipUnless('linux') decorator ensures that we're on linux
-        # if we're executing these statements.
-        from ctypes import CDLL, c_int
-        from _ctypes import dlopen, dlsym
-
         retcode = subprocess.call(["gcc", "--version"],
                                   stdout=subprocess.DEVNULL,
                                   stderr=subprocess.DEVNULL)
@@ -111,6 +108,8 @@ class TestNullDlsym(unittest.TestCase):
             self.assertEqual(os.read(pipe_r, 2), b'OK')
 
             # Case #3: Test 'py_dl_sym' from Modules/_ctypes/callproc.c
+            dlopen = test.support.get_attribute(_ctypes, 'dlopen')
+            dlsym = test.support.get_attribute(_ctypes, 'dlsym')
             L = dlopen(dstname)
             with self.assertRaisesRegex(OSError, "symbol 'foo' not found"):
                 dlsym(L, "foo")
@@ -119,5 +118,66 @@ class TestNullDlsym(unittest.TestCase):
             self.assertEqual(os.read(pipe_r, 2), b'OK')
 
 
+@unittest.skipUnless(os.name != 'nt', 'test requires dlerror() calls')
+class TestLocalization(unittest.TestCase):
+
+    @staticmethod
+    def configure_locales(func):
+        return test.support.run_with_locale(
+            'LC_ALL',
+            'fr_FR.iso88591', 'ja_JP.sjis', 'zh_CN.gbk',
+            'fr_FR.utf8', 'en_US.utf8',
+            '',
+        )(func)
+
+    @classmethod
+    def setUpClass(cls):
+        cls.libc_filename = find_library("c")
+
+    @configure_locales
+    def test_localized_error_from_dll(self):
+        dll = CDLL(self.libc_filename)
+        with self.assertRaises(AttributeError) as cm:
+            dll.this_name_does_not_exist
+        if sys.platform.startswith('linux'):
+            # On macOS, the filename is not reported by dlerror().
+            self.assertIn(self.libc_filename, str(cm.exception))
+
+    @configure_locales
+    def test_localized_error_in_dll(self):
+        dll = CDLL(self.libc_filename)
+        with self.assertRaises(ValueError) as cm:
+            c_int.in_dll(dll, 'this_name_does_not_exist')
+        if sys.platform.startswith('linux'):
+            # On macOS, the filename is not reported by dlerror().
+            self.assertIn(self.libc_filename, str(cm.exception))
+
+    @unittest.skipUnless(hasattr(_ctypes, 'dlopen'),
+                         'test requires _ctypes.dlopen()')
+    @configure_locales
+    def test_localized_error_dlopen(self):
+        missing_filename = b'missing\xff.so'
+        # Depending whether the locale, we may encode '\xff' differently
+        # but we are only interested in avoiding a UnicodeDecodeError
+        # when reporting the dlerror() error message which contains
+        # the localized filename.
+        filename_pattern = r'missing.*?\.so'
+        with self.assertRaisesRegex(OSError, filename_pattern):
+            _ctypes.dlopen(missing_filename, 2)
+
+    @unittest.skipUnless(hasattr(_ctypes, 'dlopen'),
+                         'test requires _ctypes.dlopen()')
+    @unittest.skipUnless(hasattr(_ctypes, 'dlsym'),
+                         'test requires _ctypes.dlsym()')
+    @configure_locales
+    def test_localized_error_dlsym(self):
+        dll = _ctypes.dlopen(self.libc_filename)
+        with self.assertRaises(OSError) as cm:
+            _ctypes.dlsym(dll, 'this_name_does_not_exist')
+        if sys.platform.startswith('linux'):
+            # On macOS, the filename is not reported by dlerror().
+            self.assertIn(self.libc_filename, str(cm.exception))
+
+
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_dbm_gnu.py b/Lib/test/test_dbm_gnu.py
index e20addf..66268c4 100644
--- a/Lib/test/test_dbm_gnu.py
+++ b/Lib/test/test_dbm_gnu.py
@@ -1,10 +1,11 @@
-from test import support
-from test.support import import_helper, cpython_only
-gdbm = import_helper.import_module("dbm.gnu") #skip if not supported
-import unittest
 import os
-from test.support.os_helper import TESTFN, TESTFN_NONASCII, unlink, FakePath
+import unittest
+from test import support
+from test.support import cpython_only, import_helper
+from test.support.os_helper import (TESTFN, TESTFN_NONASCII, FakePath,
+                                    create_empty_file, temp_dir, unlink)
 
+gdbm = import_helper.import_module("dbm.gnu")  # skip if not supported
 
 filename = TESTFN
 
@@ -205,6 +206,16 @@ class TestGdbm(unittest.TestCase):
                 self.assertNotIn(k, db)
             self.assertEqual(len(db), 0)
 
+    @support.run_with_locale(
+        'LC_ALL',
+        'fr_FR.iso88591', 'ja_JP.sjis', 'zh_CN.gbk',
+        'fr_FR.utf8', 'en_US.utf8',
+        '',
+    )
+    def test_localized_error(self):
+        with temp_dir() as d:
+            create_empty_file(os.path.join(d, 'test'))
+            self.assertRaises(gdbm.error, gdbm.open, filename, 'r')
 
 
 if __name__ == '__main__':