[3.14] gh-157242: Add support.inject_memory_error() function (#159582)

[3.15] gh-157242: Add support.inject_memory_error() function (#159553)

* gh-157242: Add support.inject_memory_error() function (#157431)

Add inject_memory_error() and memory_error_cm() functions to
test.support to inject memory errors: make the memory allocator fail.

(cherry picked from commit 9a1733d)

* gh-157242: Use support.inject_memory_error_cm() in tests (#157811)

Rename support.memory_error_cm() to support.inject_memory_error_cm().

(cherry picked from commit a92e0f9)

* Use support.inject_memory_error_cm()

(cherry picked from commit c1508fb)

Author: vstinner

Lib/test/support/__init__.py

@@ -3363,6 +3363,22 @@ def built_with_c_assertions():
         return bool(_testlimitedcapi._py_getbuiltwithassert())
 
 
+def inject_memory_error(start=0, stop=0):
+    """
+    Memory allocation fails after 'start' allocation requests, and until 'stop'
+    allocation requests except when 'stop' is negative or equal to 0 (default)
+    in which case allocation failures never stop.
+
+    Raise SkipTest if the _testcapi extension module is missing
+    """
+    try:
+        import _testcapi
+    except ImportError:
+        raise unittest.SkipTest("_testcapi required")
+
+    _testcapi.set_nomemory(start, stop)
+
+
 @contextlib.contextmanager
 def inject_memory_error_cm(start=0, stop=0):
     """

Lib/test/test_atexit.py

@@ -141,14 +141,14 @@ def test_atexit_with_low_memory(self):
         # callback doesn't cause an infinite loop during finalization.
         code = textwrap.dedent("""
             import atexit
-            import _testcapi
+            from test.support import inject_memory_error
 
             def callback():
                 print("hello")
 
             atexit.register(callback)
             # Simulate low memory condition
-            _testcapi.set_nomemory(0)
+            inject_memory_error()
         """)
 
         with os_helper.temp_dir() as temp_dir:

Lib/test/test_bytes.py

@@ -5,6 +5,7 @@
 """
 
 import array
+import contextlib
 import operator
 import os
 import re
@@ -48,6 +49,13 @@ def __index__(self):
         return self.value
 
 
+@contextlib.contextmanager
+def inject_memory_error(testcase, start=0):
+    with testcase.assertRaises(MemoryError):
+        with support.inject_memory_error_cm(start):
+            yield
+
+
 class BaseBytesTest:
 
     def assertTypedEqual(self, actual, expected):
@@ -1529,6 +1537,36 @@ def test_resize(self):
         self.assertRaises(MemoryError, bytearray().resize, sys.maxsize)
         self.assertRaises(MemoryError, bytearray(1000).resize, sys.maxsize)
 
+    @support.nomemtest
+    def test_resize_error(self):
+        # gh-157242: If bytearray.resize() fails (MemoryError),
+        # the bytearray must be left unchanged.
+
+        offset = 3
+        for logical_offset in (False, True):
+            with self.subTest(logical_offset=logical_offset):
+                # grow bytearray
+                ba = bytearray(b'0123456789')
+                if logical_offset:
+                    expected = ba[offset:]
+                    del ba[:offset]
+                else:
+                    expected = ba.copy()
+                with inject_memory_error(self):
+                    ba.resize(1024)
+                self.assertEqual(ba, expected)
+
+                # shrink bytearray
+                ba = bytearray(b'0123456789')
+                if logical_offset:
+                    expected = ba[offset:]
+                    del ba[:offset]
+                else:
+                    expected = ba.copy()
+                with inject_memory_error(self):
+                    ba.resize(1)
+                self.assertEqual(ba, expected)
+
     def test_setitem(self):
         def setitem_as_mapping(b, i, val):
             b[i] = val

Lib/test/test_class.py

@@ -1015,8 +1015,6 @@ class C:
     @support.nomemtest
     @isolation.runInSubprocess()
     def test_detach_materialized_dict_no_memory(self):
-        import _testcapi
-
         class A:
             def __init__(self):
                 self.a = 1
@@ -1031,11 +1029,8 @@ def __init__(self):
             d = a.__dict__
             try:
                 with support.catch_unraisable_exception() as ex:
-                    _testcapi.set_nomemory(n, n + 1)
-                    try:
+                    with support.inject_memory_error_cm(n, n + 1):
                         del a
-                    finally:
-                        _testcapi.remove_mem_hooks()
                     exc_type = ex.unraisable and ex.unraisable.exc_type
             except MemoryError:
                 # The failing allocation was not in the deallocation code.

Lib/test/test_exceptions.py

@@ -1655,14 +1655,14 @@ def test_recursion_normalizing_with_no_memory(self):
         # the size of the list of preallocated MemoryError instances, the
         # Fatal Python error message mentions MemoryError.
         code = """if 1:
-            import _testcapi
+            from test import support
             class C(): pass
             def recurse(cnt):
                 cnt -= 1
                 if cnt:
                     recurse(cnt)
                 else:
-                    _testcapi.set_nomemory(0)
+                    support.inject_memory_error()
                     C()
             recurse(16)
         """
@@ -1838,9 +1838,10 @@ def test_unhandled(self):
     @support.nomemtest
     def test_memory_error_in_PyErr_PrintEx(self):
         code = """if 1:
-            import _testcapi
+            from test import support
+            stop = %d
             class C(): pass
-            _testcapi.set_nomemory(0, %d)
+            support.inject_memory_error(0, stop)
             C()
         """
 
@@ -2005,8 +2006,8 @@ def test_exec_set_nomemory_hang(self):
         warmup_code = "a = list(range(0, 1))\n" * 60
         user_input = warmup_code + dedent("""
             try:
-                import _testcapi
-                _testcapi.set_nomemory(0)
+                from test import support
+                support.inject_memory_error()
                 b = list(range(1000, 2000))
             except Exception as e:
                 import traceback

Lib/test/test_interpreters/test_stress.py

@@ -78,15 +78,9 @@ def run():
 
     @support.nomemtest
     def test_create_interpreter_no_memory(self):
-        import _testcapi
-
-        assertion = self.assertRaises(InterpreterError)
-        try:
-            _testcapi.set_nomemory(0, 1)
-            with assertion:
+        with self.assertRaises(InterpreterError):
+            with support.inject_memory_error_cm(0, 1):
                 _interpreters.create()
-        finally:
-            _testcapi.remove_mem_hooks()
 
 
 if __name__ == '__main__':

Lib/test/test_list.py

@@ -329,11 +329,12 @@ def test_tier2_invalidates_iterator(self):
     def test_no_memory(self):
         # gh-118331: Make sure we don't crash if list allocation fails
         code = textwrap.dedent("""
-        import _testcapi, sys
+        from test import support
+        import sys
         # Prime the freelist
         l = [None]
         del l
-        _testcapi.set_nomemory(0)
+        support.inject_memory_error()
         l = [None]
         """)
         rc, _, _ = assert_python_failure("-c", code)

Lib/test/test_memoryio.py

@@ -5,7 +5,6 @@
 
 import unittest
 from test import support
-from test.support import import_helper
 
 import gc
 import io
@@ -655,18 +654,14 @@ def __buffer__(self, flags):
     @support.nomemtest
     def test_memory_error(self):
         # gh-157242: io.BytesIO() must not close the file on MemoryError
-        _testcapi = import_helper.import_module('_testcapi')
 
         # write()
         stream = self.ioclass()
         stream.write(self.buftype('abc'))
+        data = self.buftype('def')
         with self.assertRaises(MemoryError):
-            try:
-                data = self.buftype('def')
-                _testcapi.set_nomemory(0)
+            with support.inject_memory_error_cm():
                 stream.write(data)
-            finally:
-                _testcapi.remove_mem_hooks()
         stream.write(self.buftype('123'))
         self.assertEqual(stream.getvalue(), self.buftype('abc123'))
 
@@ -675,11 +670,8 @@ def test_memory_error(self):
         stream = self.ioclass()
         stream.write(data)
         with self.assertRaises(MemoryError):
-            try:
-                _testcapi.set_nomemory(0)
+            with support.inject_memory_error_cm():
                 stream.truncate(5)
-            finally:
-                _testcapi.remove_mem_hooks()
         self.assertEqual(stream.getvalue(), data)
 
 

Lib/test/test_pyexpat.py

@@ -988,18 +988,9 @@ def test_error_path_no_crash(self):
         parser.buffer_text = True
         rc_before = sys.getrefcount(parser)
 
-        # We avoid self.assertRaises(MemoryError) here because the
-        # context manager itself needs memory allocations that fail
-        # while the nomemory hook is active.
-        self.testcapi.set_nomemory(1, 10)
-        raised = False
-        try:
-            parser.ExternalEntityParserCreate(None)
-        except MemoryError:
-            raised = True
-        finally:
-            self.testcapi.remove_mem_hooks()
-        self.assertTrue(raised, "MemoryError not raised")
+        with self.assertRaises(MemoryError):
+            with support.inject_memory_error_cm(1, 10):
+                parser.ExternalEntityParserCreate(None)
 
         rc_after = sys.getrefcount(parser)
         self.assertEqual(rc_after, rc_before)

Lib/test/test_repl.py

@@ -104,10 +104,11 @@ def test_no_memory(self):
         # no memory. Check also that the fix does not break the interactive
         # loop when an exception is raised.
         user_input = """
-            import sys, _testcapi
+            import sys
+            from test import support
             1/0
             print('After the exception.')
-            _testcapi.set_nomemory(0)
+            support.inject_memory_error()
             sys.exit(0)
         """
         user_input = dedent(user_input)