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python36/00170-gc-assertions.patch
Charalampos Stratakis 0424a4f70e Rebased patches 102, 111, 170 in order to apply cleanly for the new sources. 
Dropped patches 209, 242, 247 as they are already upstream.

Dropped patches 143 and 146 for now.
2016-12-09 16:07:57 +01:00

311 lines
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diff --git a/Include/object.h b/Include/object.h
index 0c88603..e3413e8 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -1059,6 +1059,49 @@ PyAPI_FUNC(void)
_PyObject_DebugTypeStats(FILE *out);
#endif /* ifndef Py_LIMITED_API */
+/*
+ Define a pair of assertion macros.
+
+ These work like the regular C assert(), in that they will abort the
+ process with a message on stderr if the given condition fails to hold,
+ but compile away to nothing if NDEBUG is defined.
+
+ However, before aborting, Python will also try to call _PyObject_Dump() on
+ the given object. This may be of use when investigating bugs in which a
+ particular object is corrupt (e.g. buggy a tp_visit method in an extension
+ module breaking the garbage collector), to help locate the broken objects.
+
+ The WITH_MSG variant allows you to supply an additional message that Python
+ will attempt to print to stderr, after the object dump.
+*/
+#ifdef NDEBUG
+/* No debugging: compile away the assertions: */
+#define PyObject_ASSERT_WITH_MSG(obj, expr, msg) ((void)0)
+#else
+/* With debugging: generate checks: */
+#define PyObject_ASSERT_WITH_MSG(obj, expr, msg) \
+ ((expr) \
+ ? (void)(0) \
+ : _PyObject_AssertFailed((obj), \
+ (msg), \
+ (__STRING(expr)), \
+ (__FILE__), \
+ (__LINE__), \
+ (__PRETTY_FUNCTION__)))
+#endif
+
+#define PyObject_ASSERT(obj, expr) \
+ PyObject_ASSERT_WITH_MSG(obj, expr, NULL)
+
+/*
+ Declare and define the entrypoint even when NDEBUG is defined, to avoid
+ causing compiler/linker errors when building extensions without NDEBUG
+ against a Python built with NDEBUG defined
+*/
+PyAPI_FUNC(void) _PyObject_AssertFailed(PyObject *, const char *,
+ const char *, const char *, int,
+ const char *);
+
#ifdef __cplusplus
}
#endif
diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
index e727499..6efcafb 100644
--- a/Lib/test/test_gc.py
+++ b/Lib/test/test_gc.py
@@ -1,10 +1,11 @@
import unittest
from test.support import (verbose, refcount_test, run_unittest,
strip_python_stderr, cpython_only, start_threads,
- temp_dir, requires_type_collecting)
+ temp_dir, import_module, requires_type_collecting)
from test.support.script_helper import assert_python_ok, make_script
import sys
+import sysconfig
import time
import gc
import weakref
@@ -50,6 +51,8 @@ class GC_Detector(object):
# gc collects it.
self.wr = weakref.ref(C1055820(666), it_happened)
+BUILD_WITH_NDEBUG = ('-DNDEBUG' in sysconfig.get_config_vars()['PY_CFLAGS'])
+
@with_tp_del
class Uncollectable(object):
"""Create a reference cycle with multiple __del__ methods.
@@ -862,6 +865,50 @@ class GCCallbackTests(unittest.TestCase):
self.assertEqual(len(gc.garbage), 0)
+ @unittest.skipIf(BUILD_WITH_NDEBUG,
+ 'built with -NDEBUG')
+ def test_refcount_errors(self):
+ self.preclean()
+ # Verify the "handling" of objects with broken refcounts
+ import_module("ctypes") #skip if not supported
+
+ import subprocess
+ code = '''if 1:
+ a = []
+ b = [a]
+
+ # Simulate the refcount of "a" being too low (compared to the
+ # references held on it by live data), but keeping it above zero
+ # (to avoid deallocating it):
+ import ctypes
+ ctypes.pythonapi.Py_DecRef(ctypes.py_object(a))
+
+ # The garbage collector should now have a fatal error when it reaches
+ # the broken object:
+ import gc
+ gc.collect()
+ '''
+ p = subprocess.Popen([sys.executable, "-c", code],
+ stdout=subprocess.PIPE,
+ stderr=subprocess.PIPE)
+ stdout, stderr = p.communicate()
+ p.stdout.close()
+ p.stderr.close()
+ # Verify that stderr has a useful error message:
+ self.assertRegex(stderr,
+ b'Modules/gcmodule.c:[0-9]+: visit_decref: Assertion "\(\(gc\)->gc.gc_refs >> \(1\)\) != 0" failed.')
+ self.assertRegex(stderr,
+ b'refcount was too small')
+ self.assertRegex(stderr,
+ b'object : \[\]')
+ self.assertRegex(stderr,
+ b'type : list')
+ self.assertRegex(stderr,
+ b'refcount: 1')
+ self.assertRegex(stderr,
+ b'address : 0x[0-9a-f]+')
+
+
class GCTogglingTests(unittest.TestCase):
def setUp(self):
gc.enable()
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
index 0c6f444..87edd5a 100644
--- a/Modules/gcmodule.c
+++ b/Modules/gcmodule.c
@@ -341,7 +341,8 @@ update_refs(PyGC_Head *containers)
{
PyGC_Head *gc = containers->gc.gc_next;
for (; gc != containers; gc = gc->gc.gc_next) {
- assert(_PyGCHead_REFS(gc) == GC_REACHABLE);
+ PyObject_ASSERT(FROM_GC(gc),
+ _PyGCHead_REFS(gc) == GC_REACHABLE);
_PyGCHead_SET_REFS(gc, Py_REFCNT(FROM_GC(gc)));
/* Python's cyclic gc should never see an incoming refcount
* of 0: if something decref'ed to 0, it should have been
@@ -361,7 +362,8 @@ update_refs(PyGC_Head *containers)
* so serious that maybe this should be a release-build
* check instead of an assert?
*/
- assert(_PyGCHead_REFS(gc) != 0);
+ PyObject_ASSERT(FROM_GC(gc),
+ _PyGCHead_REFS(gc) != 0);
}
}
@@ -376,7 +378,9 @@ visit_decref(PyObject *op, void *data)
* generation being collected, which can be recognized
* because only they have positive gc_refs.
*/
- assert(_PyGCHead_REFS(gc) != 0); /* else refcount was too small */
+ PyObject_ASSERT_WITH_MSG(FROM_GC(gc),
+ _PyGCHead_REFS(gc) != 0,
+ "refcount was too small"); /* else refcount was too small */
if (_PyGCHead_REFS(gc) > 0)
_PyGCHead_DECREF(gc);
}
@@ -436,9 +440,10 @@ visit_reachable(PyObject *op, PyGC_Head *reachable)
* If gc_refs == GC_UNTRACKED, it must be ignored.
*/
else {
- assert(gc_refs > 0
- || gc_refs == GC_REACHABLE
- || gc_refs == GC_UNTRACKED);
+ PyObject_ASSERT(FROM_GC(gc),
+ gc_refs > 0
+ || gc_refs == GC_REACHABLE
+ || gc_refs == GC_UNTRACKED);
}
}
return 0;
@@ -480,7 +485,7 @@ move_unreachable(PyGC_Head *young, PyGC_Head *unreachable)
*/
PyObject *op = FROM_GC(gc);
traverseproc traverse = Py_TYPE(op)->tp_traverse;
- assert(_PyGCHead_REFS(gc) > 0);
+ PyObject_ASSERT(op, _PyGCHead_REFS(gc) > 0);
_PyGCHead_SET_REFS(gc, GC_REACHABLE);
(void) traverse(op,
(visitproc)visit_reachable,
@@ -543,7 +548,7 @@ move_legacy_finalizers(PyGC_Head *unreachable, PyGC_Head *finalizers)
for (gc = unreachable->gc.gc_next; gc != unreachable; gc = next) {
PyObject *op = FROM_GC(gc);
- assert(IS_TENTATIVELY_UNREACHABLE(op));
+ PyObject_ASSERT(op, IS_TENTATIVELY_UNREACHABLE(op));
next = gc->gc.gc_next;
if (has_legacy_finalizer(op)) {
@@ -619,7 +624,7 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
PyWeakReference **wrlist;
op = FROM_GC(gc);
- assert(IS_TENTATIVELY_UNREACHABLE(op));
+ PyObject_ASSERT(op, IS_TENTATIVELY_UNREACHABLE(op));
next = gc->gc.gc_next;
if (! PyType_SUPPORTS_WEAKREFS(Py_TYPE(op)))
@@ -640,9 +645,9 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
* the callback pointer intact. Obscure: it also
* changes *wrlist.
*/
- assert(wr->wr_object == op);
+ PyObject_ASSERT(wr->wr_object, wr->wr_object == op);
_PyWeakref_ClearRef(wr);
- assert(wr->wr_object == Py_None);
+ PyObject_ASSERT(wr->wr_object, wr->wr_object == Py_None);
if (wr->wr_callback == NULL)
continue; /* no callback */
@@ -676,7 +681,7 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
*/
if (IS_TENTATIVELY_UNREACHABLE(wr))
continue;
- assert(IS_REACHABLE(wr));
+ PyObject_ASSERT(op, IS_REACHABLE(wr));
/* Create a new reference so that wr can't go away
* before we can process it again.
@@ -685,7 +690,8 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
/* Move wr to wrcb_to_call, for the next pass. */
wrasgc = AS_GC(wr);
- assert(wrasgc != next); /* wrasgc is reachable, but
+ PyObject_ASSERT(op, wrasgc != next);
+ /* wrasgc is reachable, but
next isn't, so they can't
be the same */
gc_list_move(wrasgc, &wrcb_to_call);
@@ -701,11 +707,11 @@ handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
gc = wrcb_to_call.gc.gc_next;
op = FROM_GC(gc);
- assert(IS_REACHABLE(op));
- assert(PyWeakref_Check(op));
+ PyObject_ASSERT(op, IS_REACHABLE(op));
+ PyObject_ASSERT(op, PyWeakref_Check(op));
wr = (PyWeakReference *)op;
callback = wr->wr_callback;
- assert(callback != NULL);
+ PyObject_ASSERT(op, callback != NULL);
/* copy-paste of weakrefobject.c's handle_callback() */
temp = PyObject_CallFunctionObjArgs(callback, wr, NULL);
@@ -822,12 +828,14 @@ check_garbage(PyGC_Head *collectable)
for (gc = collectable->gc.gc_next; gc != collectable;
gc = gc->gc.gc_next) {
_PyGCHead_SET_REFS(gc, Py_REFCNT(FROM_GC(gc)));
- assert(_PyGCHead_REFS(gc) != 0);
+ PyObject_ASSERT(FROM_GC(gc),
+ _PyGCHead_REFS(gc) != 0);
}
subtract_refs(collectable);
for (gc = collectable->gc.gc_next; gc != collectable;
gc = gc->gc.gc_next) {
- assert(_PyGCHead_REFS(gc) >= 0);
+ PyObject_ASSERT(FROM_GC(gc),
+ _PyGCHead_REFS(gc) >= 0);
if (_PyGCHead_REFS(gc) != 0)
return -1;
}
diff --git a/Objects/object.c b/Objects/object.c
index 559794f..a47d47f 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -2022,6 +2022,35 @@ _PyTrash_thread_destroy_chain(void)
}
}
+PyAPI_FUNC(void)
+_PyObject_AssertFailed(PyObject *obj, const char *msg, const char *expr,
+ const char *file, int line, const char *function)
+{
+ fprintf(stderr,
+ "%s:%d: %s: Assertion \"%s\" failed.\n",
+ file, line, function, expr);
+ if (msg) {
+ fprintf(stderr, "%s\n", msg);
+ }
+
+ fflush(stderr);
+
+ if (obj) {
+ /* This might succeed or fail, but we're about to abort, so at least
+ try to provide any extra info we can: */
+ _PyObject_Dump(obj);
+ }
+ else {
+ fprintf(stderr, "NULL object\n");
+ }
+
+ fflush(stdout);
+ fflush(stderr);
+
+ /* Terminate the process: */
+ abort();
+}
+
#ifndef Py_TRACE_REFS
/* For Py_LIMITED_API, we need an out-of-line version of _Py_Dealloc.
Define this here, so we can undefine the macro. */
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