[Python-checkins] bpo-45061: Detect refcount bug on empty tuple singleton (GH-28503)
vstinner
webhook-mailer at python.org
Tue Sep 21 17:04:42 EDT 2021
https://github.com/python/cpython/commit/79a31480992c3fa5890fc7a6c5d9af6d337d5844
commit: 79a31480992c3fa5890fc7a6c5d9af6d337d5844
branch: main
author: Victor Stinner <vstinner at python.org>
committer: vstinner <vstinner at python.org>
date: 2021-09-21T23:04:34+02:00
summary:
bpo-45061: Detect refcount bug on empty tuple singleton (GH-28503)
Detect refcount bugs in C extensions when the empty tuple singleton
is destroyed by mistake.
Add the _Py_FatalRefcountErrorFunc() function.
files:
A Misc/NEWS.d/next/Core and Builtins/2021-09-21-22-27-25.bpo-45061.5IOUf0.rst
M Include/internal/pycore_pyerrors.h
M Objects/boolobject.c
M Objects/object.c
M Objects/tupleobject.c
M Python/pylifecycle.c
diff --git a/Include/internal/pycore_pyerrors.h b/Include/internal/pycore_pyerrors.h
index a5e97fe23fb05..0f4d41c7e0bab 100644
--- a/Include/internal/pycore_pyerrors.h
+++ b/Include/internal/pycore_pyerrors.h
@@ -90,6 +90,12 @@ extern PyObject* _Py_Offer_Suggestions(PyObject* exception);
PyAPI_FUNC(Py_ssize_t) _Py_UTF8_Edit_Cost(PyObject *str_a, PyObject *str_b,
Py_ssize_t max_cost);
+PyAPI_FUNC(void) _Py_NO_RETURN _Py_FatalRefcountErrorFunc(
+ const char *func,
+ const char *message);
+
+#define _Py_FatalRefcountError(message) _Py_FatalRefcountErrorFunc(__func__, message)
+
#ifdef __cplusplus
}
#endif
diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-09-21-22-27-25.bpo-45061.5IOUf0.rst b/Misc/NEWS.d/next/Core and Builtins/2021-09-21-22-27-25.bpo-45061.5IOUf0.rst
new file mode 100644
index 0000000000000..08924531dc3f1
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-09-21-22-27-25.bpo-45061.5IOUf0.rst
@@ -0,0 +1,4 @@
+Add a deallocator to the bool type to detect refcount bugs in C extensions
+which call Py_DECREF(Py_True) or Py_DECREF(Py_False) by mistake. Detect also
+refcount bugs when the empty tuple singleton is destroyed by mistake. Patch
+by Victor Stinner.
diff --git a/Objects/boolobject.c b/Objects/boolobject.c
index bc1666f55717c..c72243a160b88 100644
--- a/Objects/boolobject.c
+++ b/Objects/boolobject.c
@@ -1,6 +1,7 @@
/* Boolean type, a subtype of int */
#include "Python.h"
+#include "pycore_pyerrors.h" // _Py_FatalRefcountError()
#include "longintrepr.h"
/* We define bool_repr to return "False" or "True" */
@@ -156,8 +157,7 @@ static PyNumberMethods bool_as_number = {
static void _Py_NO_RETURN
bool_dealloc(PyObject* Py_UNUSED(ignore))
{
- Py_FatalError("deallocating True or False likely caused by "
- "a refcount bug in a C extension");
+ _Py_FatalRefcountError("deallocating True or False");
}
/* The type object for bool. Note that this cannot be subclassed! */
diff --git a/Objects/object.c b/Objects/object.c
index 026262b544849..aa84815e56e86 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -1563,8 +1563,7 @@ none_repr(PyObject *op)
static void _Py_NO_RETURN
none_dealloc(PyObject* Py_UNUSED(ignore))
{
- Py_FatalError("deallocating None likely caused by a refcount bug "
- "in a C extension");
+ _Py_FatalRefcountError("deallocating None");
}
static PyObject *
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 3e3aea47cc2ab..e64b93ba63e41 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -6,6 +6,7 @@
#include "pycore_gc.h" // _PyObject_GC_IS_TRACKED()
#include "pycore_initconfig.h" // _PyStatus_OK()
#include "pycore_object.h" // _PyObject_GC_TRACK()
+#include "pycore_pyerrors.h" // _Py_FatalRefcountError()
/*[clinic input]
class tuple "PyTupleObject *" "&PyTuple_Type"
@@ -287,6 +288,17 @@ tupledealloc(PyTupleObject *op)
}
#endif
}
+#if defined(Py_DEBUG) && PyTuple_MAXSAVESIZE > 0
+ else {
+ assert(len == 0);
+ struct _Py_tuple_state *state = get_tuple_state();
+ // The empty tuple singleton must only be deallocated by
+ // _PyTuple_Fini(): not before, not after
+ if (op == state->free_list[0] && state->numfree[0] != 0) {
+ _Py_FatalRefcountError("deallocating the empty tuple singleton");
+ }
+ }
+#endif
Py_TYPE(op)->tp_free((PyObject *)op);
#if PyTuple_MAXSAVESIZE > 0
@@ -1048,11 +1060,16 @@ _PyTuple_Fini(PyInterpreterState *interp)
struct _Py_tuple_state *state = &interp->tuple;
// The empty tuple singleton must not be tracked by the GC
assert(!_PyObject_GC_IS_TRACKED(state->free_list[0]));
+
+#ifdef Py_DEBUG
+ state->numfree[0] = 0;
+#endif
Py_CLEAR(state->free_list[0]);
- _PyTuple_ClearFreeList(interp);
#ifdef Py_DEBUG
state->numfree[0] = -1;
#endif
+
+ _PyTuple_ClearFreeList(interp);
#endif
}
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index b10a19c0d8d5f..bfddc1922d25a 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -2805,6 +2805,16 @@ _Py_FatalErrorFormat(const char *func, const char *format, ...)
}
+void _Py_NO_RETURN
+_Py_FatalRefcountErrorFunc(const char *func, const char *msg)
+{
+ _Py_FatalErrorFormat(func,
+ "%s: bug likely caused by a refcount error "
+ "in a C extension",
+ msg);
+}
+
+
void _Py_NO_RETURN
Py_ExitStatusException(PyStatus status)
{
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