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gh-135125: Fix Py_STACKREF_DEBUG build #139475

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Merged
markshannon merged 5 commits into from
Oct 23, 2025
Merged

gh-135125: Fix Py_STACKREF_DEBUG build #139475

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e0ea1b1
Fixes for PyStackRefs in debug builds.
efimov-mikhail Oct 1, 2025
56a2076
The same pattern of refcounting for stackrefs as in production build
efimov-mikhail Oct 3, 2025
89cd750
Merge branch 'main' into issue_135379_stackref_debug_fixes
efimov-mikhail Oct 22, 2025
a2754b7
Adoption after merge main, review addressed
efimov-mikhail Oct 22, 2025
14b89e5
Address review
efimov-mikhail Oct 23, 2025
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Adoption after merge main, review addressed
  • Loading branch information
@efimov-mikhail
efimov-mikhail committed Oct 22, 2025
commit a2754b7cfe34ee13b1c12342e56b5e102989ab90
41 changes: 22 additions & 19 deletions Include/internal/pycore_stackref.h
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Original file line number Diff line number Diff line change
Expand Up @@ -50,28 +50,29 @@ extern "C" {
CPython refcounting operations on it!
*/


#if !defined(Py_GIL_DISABLED) && defined(Py_STACKREF_DEBUG)

#define Py_INT_TAG 3
#define Py_TAG_INVALID 2
#define Py_TAG_REFCNT 1
#define Py_TAG_BITS 3

#define Py_TAGGED_SHIFT 2

#if !defined(Py_GIL_DISABLED) && defined(Py_STACKREF_DEBUG)

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);
extern void _Py_stackref_associate(PyInterpreterState *interp, PyObject *obj, _PyStackRef ref);

static const _PyStackRef PyStackRef_NULL = { .index = 0 };
static const _PyStackRef PyStackRef_ERROR = { .index = 4 };
static const _PyStackRef PyStackRef_ERROR = { .index = (1 << Py_TAGGED_SHIFT) };

#define PyStackRef_None ((_PyStackRef){ .index = 8 } )
#define PyStackRef_False ((_PyStackRef){ .index = 12 })
#define PyStackRef_True ((_PyStackRef){ .index = 16 })
#define PyStackRef_None ((_PyStackRef){ .index = (2 << Py_TAGGED_SHIFT) } )
#define PyStackRef_False ((_PyStackRef){ .index = (3 << Py_TAGGED_SHIFT) })
#define PyStackRef_True ((_PyStackRef){ .index = (4 << Py_TAGGED_SHIFT) })

#define INITIAL_STACKREF_INDEX 20
#define INITIAL_STACKREF_INDEX (5 << Py_TAGGED_SHIFT)

static inline _PyStackRef
PyStackRef_Wrap(void *ptr)
Expand Down Expand Up @@ -111,7 +112,13 @@ PyStackRef_IsNull(_PyStackRef ref)
static inline bool
PyStackRef_IsError(_PyStackRef ref)
{
return ref.index == 4;
return ref.index == (1 << Py_TAGGED_SHIFT);
}

static inline bool
PyStackRef_IsMalformed(_PyStackRef ref)
{
return (ref.index & Py_TAG_BITS) == Py_TAG_INVALID;
}

static inline bool
Expand Down Expand Up @@ -315,6 +322,7 @@ _PyStackRef_MakeHeapSafe(_PyStackRef ref, const char *filename, int linenumber)
static inline _PyStackRef
_PyStackRef_FromPyObjectNewMortal(PyObject *obj, const char *filename, int linenumber)
{
assert(obj != NULL);
assert(!_Py_IsStaticImmortal(obj));
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Py_XINCREF(obj);
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return _Py_stackref_create(obj, 0, filename, linenumber);
Expand All @@ -337,11 +345,6 @@ PyStackRef_IsNullOrInt(_PyStackRef ref);

#else

#define Py_INT_TAG 3
#define Py_TAG_INVALID 2
#define Py_TAG_REFCNT 1
#define Py_TAG_BITS 3

static const _PyStackRef PyStackRef_ERROR = { .bits = Py_TAG_INVALID };

/* Wrap a pointer in a stack ref.
Expand Down Expand Up @@ -399,25 +402,25 @@ PyStackRef_IsTaggedInt(_PyStackRef i)
static inline _PyStackRef
PyStackRef_TagInt(intptr_t i)
{
assert(Py_ARITHMETIC_RIGHT_SHIFT(intptr_t, (i << 2), 2) == i);
return (_PyStackRef){ .bits = ((((uintptr_t)i) << 2) | Py_INT_TAG) };
assert(Py_ARITHMETIC_RIGHT_SHIFT(intptr_t, (i << Py_TAGGED_SHIFT), Py_TAGGED_SHIFT) == i);
return (_PyStackRef){ .bits = ((((uintptr_t)i) << Py_TAGGED_SHIFT) | Py_INT_TAG) };
}

static inline intptr_t
PyStackRef_UntagInt(_PyStackRef i)
{
assert(PyStackRef_IsTaggedInt(i));
intptr_t val = (intptr_t)i.bits;
return Py_ARITHMETIC_RIGHT_SHIFT(intptr_t, val, 2);
return Py_ARITHMETIC_RIGHT_SHIFT(intptr_t, val, Py_TAGGED_SHIFT);
}


static inline _PyStackRef
PyStackRef_IncrementTaggedIntNoOverflow(_PyStackRef ref)
{
assert((ref.bits & Py_TAG_BITS) == Py_INT_TAG); // Is tagged int
assert((ref.bits & (~Py_TAG_BITS)) != (INT_MAX & (~Py_TAG_BITS))); // Isn't about to overflow
return (_PyStackRef){ .bits = ref.bits + 4 };
assert((ref.bits & (~Py_TAG_BITS)) != (INTPTR_MAX & (~Py_TAG_BITS))); // Isn't about to overflow
return (_PyStackRef){ .bits = ref.bits + (1 << Py_TAGGED_SHIFT) };
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}

#define PyStackRef_IsDeferredOrTaggedInt(ref) (((ref).bits & Py_TAG_REFCNT) != 0)
Expand Down
12 changes: 6 additions & 6 deletions Python/stackrefs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -116,7 +116,7 @@ _Py_stackref_create(PyObject *obj, uint16_t flags, const char *filename, int lin
}
PyInterpreterState *interp = PyInterpreterState_Get();
uint64_t new_id = interp->next_stackref;
interp->next_stackref = new_id + 4;
interp->next_stackref = new_id + (1 << Py_TAGGED_SHIFT);
TableEntry *entry = make_table_entry(obj, filename, linenumber);
if (entry == NULL) {
Py_FatalError("No memory left for stackref debug table");
Expand Down Expand Up @@ -197,16 +197,16 @@ _Py_stackref_report_leaks(PyInterpreterState *interp)

_PyStackRef PyStackRef_TagInt(intptr_t i)
{
assert(Py_ARITHMETIC_RIGHT_SHIFT(intptr_t, (i << 2), 2) == i);
return (_PyStackRef){ .index = (i << 2) | Py_INT_TAG };
assert(Py_ARITHMETIC_RIGHT_SHIFT(intptr_t, (i << Py_TAGGED_SHIFT), Py_TAGGED_SHIFT) == i);
return (_PyStackRef){ .index = (i << Py_TAGGED_SHIFT) | Py_INT_TAG };
}

intptr_t
PyStackRef_UntagInt(_PyStackRef i)
{
assert(PyStackRef_IsTaggedInt(i));
intptr_t val = (intptr_t)i.index;
return Py_ARITHMETIC_RIGHT_SHIFT(intptr_t, val, 2);
return Py_ARITHMETIC_RIGHT_SHIFT(intptr_t, val, Py_TAGGED_SHIFT);
}

bool
Expand All @@ -219,8 +219,8 @@ _PyStackRef
PyStackRef_IncrementTaggedIntNoOverflow(_PyStackRef ref)
{
assert(PyStackRef_IsTaggedInt(ref));
assert((ref.index & (~Py_TAG_BITS)) != (INT_MAX & (~Py_TAG_BITS))); // Isn't about to overflow
return (_PyStackRef){ .index = ref.index + 4 };
assert((ref.index & (~Py_TAG_BITS)) != (INTPTR_MAX & (~Py_TAG_BITS))); // Isn't about to overflow
return (_PyStackRef){ .index = ref.index + (1 << Py_TAGGED_SHIFT) };
}


Expand Down
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