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gh-131527: Stackref debug borrow checker (#140599)

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Add borrow checking to the stackref debug mode

---------

Co-authored-by: mpage <mpage@meta.com>
This commit is contained in:
Mikhail Efimov
2025-11-05 22:12:56 +03:00
committed by GitHub
parent baa9f33897
commit 3cb1ab0e5d
3 changed files with 110 additions and 14 deletions
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29
Include/internal/pycore_stackref.h
View File

@@ -63,6 +63,8 @@ PyAPI_FUNC(PyObject *) _Py_stackref_get_object(_PyStackRef ref);
PyAPI_FUNC(PyObject *) _Py_stackref_close(_PyStackRef ref, const char *filename, int linenumber);
PyAPI_FUNC(_PyStackRef) _Py_stackref_create(PyObject *obj, uint16_t flags, const char *filename, int linenumber);
PyAPI_FUNC(void) _Py_stackref_record_borrow(_PyStackRef ref, const char *filename, int linenumber);
PyAPI_FUNC(_PyStackRef) _Py_stackref_get_borrowed_from(_PyStackRef ref, const char *filename, int linenumber);
PyAPI_FUNC(void) _Py_stackref_set_borrowed_from(_PyStackRef ref, _PyStackRef borrowed_from, const char *filename, int linenumber);
extern void _Py_stackref_associate(PyInterpreterState *interp, PyObject *obj, _PyStackRef ref);
static const _PyStackRef PyStackRef_NULL = { .index = 0 };
@@ -248,7 +250,12 @@ _PyStackRef_DUP(_PyStackRef ref, const char *filename, int linenumber)
} else {
flags = Py_TAG_REFCNT;
}
return _Py_stackref_create(obj, flags, filename, linenumber);
_PyStackRef new_ref = _Py_stackref_create(obj, flags, filename, linenumber);
if (flags == Py_TAG_REFCNT && !_Py_IsImmortal(obj)) {
_PyStackRef borrowed_from = _Py_stackref_get_borrowed_from(ref, filename, linenumber);
_Py_stackref_set_borrowed_from(new_ref, borrowed_from, filename, linenumber);
}
return new_ref;
}
#define PyStackRef_DUP(REF) _PyStackRef_DUP(REF, __FILE__, __LINE__)
@@ -259,6 +266,7 @@ _PyStackRef_CLOSE_SPECIALIZED(_PyStackRef ref, destructor destruct, const char *
assert(!PyStackRef_IsNull(ref));
assert(!PyStackRef_IsTaggedInt(ref));
PyObject *obj = _Py_stackref_close(ref, filename, linenumber);
assert(Py_REFCNT(obj) > 0);
if (PyStackRef_RefcountOnObject(ref)) {
_Py_DECREF_SPECIALIZED(obj, destruct);
}
@@ -274,7 +282,11 @@ _PyStackRef_Borrow(_PyStackRef ref, const char *filename, int linenumber)
return ref;
}
PyObject *obj = _Py_stackref_get_object(ref);
return _Py_stackref_create(obj, Py_TAG_REFCNT, filename, linenumber);
_PyStackRef new_ref = _Py_stackref_create(obj, Py_TAG_REFCNT, filename, linenumber);
if (!_Py_IsImmortal(obj)) {
_Py_stackref_set_borrowed_from(new_ref, ref, filename, linenumber);
}
return new_ref;
}
#define PyStackRef_Borrow(REF) _PyStackRef_Borrow((REF), __FILE__, __LINE__)
@@ -310,13 +322,22 @@ PyStackRef_IsHeapSafe(_PyStackRef ref)
static inline _PyStackRef
_PyStackRef_MakeHeapSafe(_PyStackRef ref, const char *filename, int linenumber)
{
if (PyStackRef_IsHeapSafe(ref)) {
// Special references that can't be closed.
if (ref.index < INITIAL_STACKREF_INDEX) {
return ref;
}
bool heap_safe = PyStackRef_IsHeapSafe(ref);
PyObject *obj = _Py_stackref_close(ref, filename, linenumber);
uint16_t flags = 0;
if (heap_safe) {
// Close old ref and create a new one with the same flags.
// This is necessary for correct borrow checking.
flags = ref.index & Py_TAG_BITS;
} else {
Py_INCREF(obj);
return _Py_stackref_create(obj, 0, filename, linenumber);
}
return _Py_stackref_create(obj, flags, filename, linenumber);
}
#define PyStackRef_MakeHeapSafe(REF) _PyStackRef_MakeHeapSafe(REF, __FILE__, __LINE__)

2
Misc/NEWS.d/next/Core_and_Builtins/2025-10-25-21-31-43.gh-issue-131527.V-JVNP.rst Normal file
View File

@@ -0,0 +1,2 @@
Dynamic borrow checking for stackrefs is added to ``Py_STACKREF_DEBUG``
mode. Patch by Mikhail Efimov.

91
Python/stackrefs.c
View File

@@ -19,6 +19,8 @@ typedef struct _table_entry {
int linenumber;
const char *filename_borrow;
int linenumber_borrow;
int borrows;
_PyStackRef borrowed_from;
} TableEntry;
TableEntry *
@@ -34,6 +36,8 @@ make_table_entry(PyObject *obj, const char *filename, int linenumber)
result->linenumber = linenumber;
result->filename_borrow = NULL;
result->linenumber_borrow = 0;
result->borrows = 0;
result->borrowed_from = PyStackRef_NULL;
return result;
}
@@ -47,11 +51,13 @@ _Py_stackref_get_object(_PyStackRef ref)
PyInterpreterState *interp = PyInterpreterState_Get();
assert(interp != NULL);
if (ref.index >= interp->next_stackref) {
_Py_FatalErrorFormat(__func__, "Garbled stack ref with ID %" PRIu64 "\n", ref.index);
_Py_FatalErrorFormat(__func__,
"Garbled stack ref with ID %" PRIu64 "\n", ref.index);
}
TableEntry *entry = _Py_hashtable_get(interp->open_stackrefs_table, (void *)ref.index);
if (entry == NULL) {
_Py_FatalErrorFormat(__func__, "Accessing closed stack ref with ID %" PRIu64 "\n", ref.index);
_Py_FatalErrorFormat(__func__,
"Accessing closed stack ref with ID %" PRIu64 "\n", ref.index);
}
return entry->obj;
}
@@ -68,13 +74,16 @@ _Py_stackref_close(_PyStackRef ref, const char *filename, int linenumber)
assert(!PyStackRef_IsError(ref));
PyInterpreterState *interp = PyInterpreterState_Get();
if (ref.index >= interp->next_stackref) {
_Py_FatalErrorFormat(__func__, "Invalid StackRef with ID %" PRIu64 " at %s:%d\n", (void *)ref.index, filename, linenumber);
_Py_FatalErrorFormat(__func__,
"Invalid StackRef with ID %" PRIu64 " at %s:%d\n",
ref.index, filename, linenumber);
}
PyObject *obj;
if (ref.index < INITIAL_STACKREF_INDEX) {
if (ref.index == 0) {
_Py_FatalErrorFormat(__func__, "Passing NULL to PyStackRef_CLOSE at %s:%d\n", filename, linenumber);
_Py_FatalErrorFormat(__func__,
"Passing NULL to _Py_stackref_close at %s:%d\n",
filename, linenumber);
}
// Pre-allocated reference to None, False or True -- Do not clear
TableEntry *entry = _Py_hashtable_get(interp->open_stackrefs_table, (void *)ref.index);
@@ -88,10 +97,27 @@ _Py_stackref_close(_PyStackRef ref, const char *filename, int linenumber)
if (entry != NULL) {
_Py_FatalErrorFormat(__func__,
"Double close of ref ID %" PRIu64 " at %s:%d. Referred to instance of %s at %p. Closed at %s:%d\n",
(void *)ref.index, filename, linenumber, entry->classname, entry->obj, entry->filename, entry->linenumber);
ref.index, filename, linenumber, entry->classname, entry->obj, entry->filename, entry->linenumber);
}
#endif
_Py_FatalErrorFormat(__func__, "Invalid StackRef with ID %" PRIu64 "\n", (void *)ref.index);
_Py_FatalErrorFormat(__func__,
"Invalid StackRef with ID %" PRIu64 " at %s:%d\n",
ref.index, filename, linenumber);
}
if (!PyStackRef_IsNull(entry->borrowed_from)) {
_PyStackRef borrowed_from = entry->borrowed_from;
TableEntry *entry_borrowed = _Py_hashtable_get(interp->open_stackrefs_table, (void *)borrowed_from.index);
if (entry_borrowed == NULL) {
_Py_FatalErrorFormat(__func__,
"Invalid borrowed StackRef with ID %" PRIu64 " at %s:%d\n",
borrowed_from.index, filename, linenumber);
}
entry_borrowed->borrows--;
}
if (entry->borrows > 0) {
_Py_FatalErrorFormat(__func__,
"StackRef with ID %" PRIu64 " closed with %d borrowed refs at %s:%d. Opened at %s:%d\n",
ref.index, entry->borrows, filename, linenumber, entry->filename, entry->linenumber);
}
obj = entry->obj;
free(entry);
@@ -143,15 +169,62 @@ _Py_stackref_record_borrow(_PyStackRef ref, const char *filename, int linenumber
if (entry != NULL) {
_Py_FatalErrorFormat(__func__,
"Borrow of closed ref ID %" PRIu64 " at %s:%d. Referred to instance of %s at %p. Closed at %s:%d\n",
(void *)ref.index, filename, linenumber, entry->classname, entry->obj, entry->filename, entry->linenumber);
ref.index, filename, linenumber, entry->classname, entry->obj, entry->filename, entry->linenumber);
}
#endif
_Py_FatalErrorFormat(__func__, "Invalid StackRef with ID %" PRIu64 " at %s:%d\n", (void *)ref.index, filename, linenumber);
_Py_FatalErrorFormat(__func__,
"Invalid StackRef with ID %" PRIu64 " at %s:%d\n",
ref.index, filename, linenumber);
}
entry->filename_borrow = filename;
entry->linenumber_borrow = linenumber;
}
_PyStackRef
_Py_stackref_get_borrowed_from(_PyStackRef ref, const char *filename, int linenumber)
{
assert(!PyStackRef_IsError(ref));
PyInterpreterState *interp = PyInterpreterState_Get();
TableEntry *entry = _Py_hashtable_get(interp->open_stackrefs_table, (void *)ref.index);
if (entry == NULL) {
_Py_FatalErrorFormat(__func__,
"Invalid StackRef with ID %" PRIu64 " at %s:%d\n",
ref.index, filename, linenumber);
}
return entry->borrowed_from;
}
// This function should be used no more than once per ref.
void
_Py_stackref_set_borrowed_from(_PyStackRef ref, _PyStackRef borrowed_from, const char *filename, int linenumber)
{
assert(!PyStackRef_IsError(ref));
PyInterpreterState *interp = PyInterpreterState_Get();
TableEntry *entry = _Py_hashtable_get(interp->open_stackrefs_table, (void *)ref.index);
if (entry == NULL) {
_Py_FatalErrorFormat(__func__,
"Invalid StackRef (ref) with ID %" PRIu64 " at %s:%d\n",
ref.index, filename, linenumber);
}
assert(PyStackRef_IsNull(entry->borrowed_from));
if (PyStackRef_IsNull(borrowed_from)) {
return;
}
TableEntry *entry_borrowed = _Py_hashtable_get(interp->open_stackrefs_table, (void *)borrowed_from.index);
if (entry_borrowed == NULL) {
_Py_FatalErrorFormat(__func__,
"Invalid StackRef (borrowed_from) with ID %" PRIu64 " at %s:%d\n",
borrowed_from.index, filename, linenumber);
}
entry->borrowed_from = borrowed_from;
entry_borrowed->borrows++;
}
void
_Py_stackref_associate(PyInterpreterState *interp, PyObject *obj, _PyStackRef ref)