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bpo-36389: _PyObject_CheckConsistency() available in release mode (GH-16612)

Browse source 
bpo-36389, bpo-38376: The _PyObject_CheckConsistency() function is
now also available in release mode. For example, it can be used to
debug a crash in the visit_decref() function of the GC.

Modify the following functions to also work in release mode:

* _PyDict_CheckConsistency()
* _PyObject_CheckConsistency()
* _PyType_CheckConsistency()
* _PyUnicode_CheckConsistency()

Other changes:

* _PyMem_IsPtrFreed(ptr) now also returns 1 if ptr is NULL
  (equals to 0).
* _PyBytesWriter_CheckConsistency() now returns 1 and is only used
  with assert().
* Reorder _PyObject_Dump() to write safe fields first, and only
  attempt to render repr() at the end.
This commit is contained in:
Victor Stinner 2019-10-07 18:42:01 +02:00 • committed by GitHub
parent 321def805a
commit 6876257eaa
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
14 changed files with 155 additions and 140 deletions
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83
Objects/object.c
View file

@ -25,13 +25,14 @@ _Py_IDENTIFIER(__isabstractmethod__);
int
_PyObject_CheckConsistency(PyObject *op, int check_content)
{
_PyObject_ASSERT(op, op != NULL);
_PyObject_ASSERT(op, !_PyObject_IsFreed(op));
_PyObject_ASSERT(op, Py_REFCNT(op) >= 1);
#define CHECK(expr) \
do { if (!(expr)) { _PyObject_ASSERT_FAILED_MSG(op, Py_STRINGIFY(expr)); } } while (0)
PyTypeObject *type = op->ob_type;
_PyObject_ASSERT(op, type != NULL);
_PyType_CheckConsistency(type);
CHECK(!_PyObject_IsFreed(op));
CHECK(Py_REFCNT(op) >= 1);
CHECK(op->ob_type != NULL);
_PyType_CheckConsistency(op->ob_type);
if (PyUnicode_Check(op)) {
_PyUnicode_CheckConsistency(op, check_content);
@ -40,6 +41,8 @@ _PyObject_CheckConsistency(PyObject *op, int check_content)
_PyDict_CheckConsistency(op, check_content);
}
return 1;
#undef CHECK
}
@ -463,41 +466,41 @@ _PyObject_IsFreed(PyObject *op)
void
_PyObject_Dump(PyObject* op)
{
if (op == NULL) {
fprintf(stderr, "<object at NULL>\n");
fflush(stderr);
return;
}
if (_PyObject_IsFreed(op)) {
/* It seems like the object memory has been freed:
don't access it to prevent a segmentation fault. */
fprintf(stderr, "<object at %p is freed>\n", op);
fflush(stderr);
return;
}
PyGILState_STATE gil;
PyObject *error_type, *error_value, *error_traceback;
fprintf(stderr, "object : ");
fflush(stderr);
gil = PyGILState_Ensure();
PyErr_Fetch(&error_type, &error_value, &error_traceback);
(void)PyObject_Print(op, stderr, 0);
fflush(stderr);
PyErr_Restore(error_type, error_value, error_traceback);
PyGILState_Release(gil);
/* first, write fields which are the least likely to crash */
fprintf(stderr, "object address : %p\n", (void *)op);
/* XXX(twouters) cast refcount to long until %zd is
universally available */
fprintf(stderr, "\n"
"type : %s\n"
"refcount: %ld\n"
"address : %p\n",
Py_TYPE(op)==NULL ? "NULL" : Py_TYPE(op)->tp_name,
(long)op->ob_refcnt,
(void *)op);
fprintf(stderr, "object refcount : %ld\n", (long)op->ob_refcnt);
fflush(stderr);
PyTypeObject *type = Py_TYPE(op);
fprintf(stderr, "object type : %p\n", type);
fprintf(stderr, "object type name: %s\n",
type==NULL ? "NULL" : type->tp_name);
/* the most dangerous part */
fprintf(stderr, "object repr : ");
fflush(stderr);
PyGILState_STATE gil = PyGILState_Ensure();
PyObject *error_type, *error_value, *error_traceback;
PyErr_Fetch(&error_type, &error_value, &error_traceback);
(void)PyObject_Print(op, stderr, 0);
fflush(stderr);
PyErr_Restore(error_type, error_value, error_traceback);
PyGILState_Release(gil);
fprintf(stderr, "\n");
fflush(stderr);
}
@ -2146,6 +2149,7 @@ _PyObject_AssertFailed(PyObject *obj, const char *expr, const char *msg,
fprintf(stderr, "%s: ", function);
}
fflush(stderr);
if (expr) {
fprintf(stderr, "Assertion \"%s\" failed", expr);
}
@ -2153,26 +2157,18 @@ _PyObject_AssertFailed(PyObject *obj, const char *expr, const char *msg,
fprintf(stderr, "Assertion failed");
}
fflush(stderr);
if (msg) {
fprintf(stderr, ": %s", msg);
}
fprintf(stderr, "\n");
fflush(stderr);
if (obj == NULL) {
fprintf(stderr, "<object at NULL>\n");
}
else if (_PyObject_IsFreed(obj)) {
if (_PyObject_IsFreed(obj)) {
/* It seems like the object memory has been freed:
don't access it to prevent a segmentation fault. */
fprintf(stderr, "<object at %p is freed>\n", obj);
}
else if (Py_TYPE(obj) == NULL) {
fprintf(stderr, "<object at %p: ob_type=NULL>\n", obj);
}
else if (_PyObject_IsFreed((PyObject *)Py_TYPE(obj))) {
fprintf(stderr, "<object at %p: type at %p is freed>\n",
obj, (void *)Py_TYPE(obj));
fflush(stderr);
}
else {
/* Display the traceback where the object has been allocated.
@ -2192,7 +2188,6 @@ _PyObject_AssertFailed(PyObject *obj, const char *expr, const char *msg,
try to provide any extra info we can: */
_PyObject_Dump(obj);
}
fflush(stderr);
Py_FatalError("_PyObject_AssertFailed");
}