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bpo-42972: Fully implement GC protocol for re types #26368

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Merged
merged 2 commits into from
May 27, 2021
Merged

bpo-42972: Fully implement GC protocol for re types #26368

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bpo-42972: Fully implement GC protocol for re types
May 13, 2021
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Address review: visit members in order, use tp_free, don't clear weak…
May 27, 2021
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bpo-42972: Fully implement GC protocol for re types
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Erlend E. Aasland committed May 25, 2021
commit 6b6328aa84b22c614cf50594659d0ce46a907a70
102 changes: 82 additions & 20 deletions 102 Modules/_sre.c
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Original file line number Diff line number Diff line change
Expand Up @@ -563,17 +563,36 @@ pattern_error(Py_ssize_t status)
}
}

static int
pattern_traverse(PatternObject *self, visitproc visit, void *arg)
{
Py_VISIT(self->groupindex);
Py_VISIT(self->indexgroup);
Py_VISIT(self->pattern);
Py_VISIT(Py_TYPE(self));
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return 0;
}

static int
pattern_clear(PatternObject *self)
{
if (self->weakreflist != NULL) {
PyObject_ClearWeakRefs((PyObject *) self);
}
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Py_CLEAR(self->groupindex);
Py_CLEAR(self->indexgroup);
Py_CLEAR(self->pattern);
return 0;
}

static void
pattern_dealloc(PatternObject* self)
{
PyTypeObject *tp = Py_TYPE(self);

if (self->weakreflist != NULL)
PyObject_ClearWeakRefs((PyObject *) self);
Py_XDECREF(self->pattern);
Py_XDECREF(self->groupindex);
Py_XDECREF(self->indexgroup);
PyObject_Free(self);
PyObject_GC_UnTrack(self);
(void)pattern_clear(self);
PyObject_GC_Del(self);
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Py_DECREF(tp);
}

Expand Down Expand Up @@ -1397,7 +1416,7 @@ _sre_compile_impl(PyObject *module, PyObject *pattern, int flags,

n = PyList_GET_SIZE(code);
/* coverity[ampersand_in_size] */
self = PyObject_NewVar(PatternObject, module_state->Pattern_Type, n);
self = PyObject_GC_NewVar(PatternObject, module_state->Pattern_Type, n);
if (!self)
return NULL;
self->weakreflist = NULL;
Expand All @@ -1417,6 +1436,7 @@ _sre_compile_impl(PyObject *module, PyObject *pattern, int flags,
break;
}
}
PyObject_GC_Track(self);
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@pablogsal I'm unsure if this it the correct place to start tracking the newly created pattern object. My reasoning was that AFAICS, it seems to be fully initialised here, unless I've missed something.

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IMO it's the right place.

It must be called before the first DECREF(self), otherwise PyObject_GC_UnTrack() crash in dealloc.

Usually, it's better to only track an object once it's fully initialized, but here it's more convient to do it here to be able to simply call DECREF() on error. The bare minimum is that traverse must be crash when an object started to be tracked. I added a test in debug mode for that: see traverse(visit_validate) in PyObject_GC_Track().


if (PyErr_Occurred()) {
Py_DECREF(self);
Expand Down Expand Up @@ -1938,15 +1958,33 @@ _validate(PatternObject *self)
/* -------------------------------------------------------------------- */
/* match methods */

static int
match_traverse(MatchObject *self, visitproc visit, void *arg)
{
Py_VISIT(self->pattern);
Py_VISIT(self->regs);
Py_VISIT(self->string);
Py_VISIT(Py_TYPE(self));
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return 0;
}

static int
match_clear(MatchObject *self)
{
Py_CLEAR(self->pattern);
Py_CLEAR(self->regs);
Py_CLEAR(self->string);
return 0;
}

static void
match_dealloc(MatchObject* self)
{
PyTypeObject *tp = Py_TYPE(self);

Py_XDECREF(self->regs);
Py_XDECREF(self->string);
Py_DECREF(self->pattern);
PyObject_Free(self);
PyObject_GC_UnTrack(self);
(void)match_clear(self);
PyObject_GC_Del(self);
Py_DECREF(tp);
}

Expand Down Expand Up @@ -2392,9 +2430,9 @@ pattern_new_match(_sremodulestate* module_state,

/* create match object (with room for extra group marks) */
/* coverity[ampersand_in_size] */
match = PyObject_NewVar(MatchObject,
module_state->Match_Type,
2*(pattern->groups+1));
match = PyObject_GC_NewVar(MatchObject,
module_state->Match_Type,
2*(pattern->groups+1));
if (!match)
return NULL;

Expand Down Expand Up @@ -2427,6 +2465,7 @@ pattern_new_match(_sremodulestate* module_state,

match->lastindex = state->lastindex;

PyObject_GC_Track(match);
return (PyObject*) match;

} else if (status == 0) {
Expand All @@ -2445,14 +2484,30 @@ pattern_new_match(_sremodulestate* module_state,
/* -------------------------------------------------------------------- */
/* scanner methods (experimental) */

static int
scanner_traverse(ScannerObject *self, visitproc visit, void *arg)
{
Py_VISIT(self->pattern);
Py_VISIT(Py_TYPE(self));
return 0;
}

static int
scanner_clear(ScannerObject *self)
{
Py_CLEAR(self->pattern);
return 0;
}

static void
scanner_dealloc(ScannerObject* self)
{
PyTypeObject *tp = Py_TYPE(self);

PyObject_GC_UnTrack(self);
state_fini(&self->state);
Py_XDECREF(self->pattern);
PyObject_Free(self);
(void)scanner_clear(self);
PyObject_GC_Del(self);
Py_DECREF(tp);
}

Expand Down Expand Up @@ -2549,7 +2604,7 @@ pattern_scanner(_sremodulestate *module_state,
ScannerObject* scanner;

/* create scanner object */
scanner = PyObject_New(ScannerObject, module_state->Scanner_Type);
scanner = PyObject_GC_New(ScannerObject, module_state->Scanner_Type);
if (!scanner)
return NULL;
scanner->pattern = NULL;
Expand All @@ -2563,6 +2618,7 @@ pattern_scanner(_sremodulestate *module_state,
Py_INCREF(self);
scanner->pattern = (PyObject*) self;

PyObject_GC_Track(scanner);
return (PyObject*) scanner;
}

Expand Down Expand Up @@ -2684,6 +2740,8 @@ static PyType_Slot pattern_slots[] = {
{Py_tp_methods, pattern_methods},
{Py_tp_members, pattern_members},
{Py_tp_getset, pattern_getset},
{Py_tp_traverse, pattern_traverse},
{Py_tp_clear, pattern_clear},
{0, NULL},
};

Expand All @@ -2692,7 +2750,7 @@ static PyType_Spec pattern_spec = {
.basicsize = sizeof(PatternObject),
.itemsize = sizeof(SRE_CODE),
.flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE |
Py_TPFLAGS_DISALLOW_INSTANTIATION),
Py_TPFLAGS_DISALLOW_INSTANTIATION | Py_TPFLAGS_HAVE_GC),
.slots = pattern_slots,
};

Expand Down Expand Up @@ -2742,6 +2800,8 @@ static PyType_Slot match_slots[] = {
{Py_tp_methods, match_methods},
{Py_tp_members, match_members},
{Py_tp_getset, match_getset},
{Py_tp_traverse, match_traverse},
{Py_tp_clear, match_clear},

/* As mapping.
*
Expand All @@ -2758,7 +2818,7 @@ static PyType_Spec match_spec = {
.basicsize = sizeof(MatchObject),
.itemsize = sizeof(Py_ssize_t),
.flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE |
Py_TPFLAGS_DISALLOW_INSTANTIATION),
Py_TPFLAGS_DISALLOW_INSTANTIATION | Py_TPFLAGS_HAVE_GC),
.slots = match_slots,
};

Expand All @@ -2778,14 +2838,16 @@ static PyType_Slot scanner_slots[] = {
{Py_tp_dealloc, scanner_dealloc},
{Py_tp_methods, scanner_methods},
{Py_tp_members, scanner_members},
{Py_tp_traverse, scanner_traverse},
{Py_tp_clear, scanner_clear},
{0, NULL},
};

static PyType_Spec scanner_spec = {
.name = "_" SRE_MODULE ".SRE_Scanner",
.basicsize = sizeof(ScannerObject),
.flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE |
Py_TPFLAGS_DISALLOW_INSTANTIATION),
Py_TPFLAGS_DISALLOW_INSTANTIATION | Py_TPFLAGS_HAVE_GC),
.slots = scanner_slots,
};

Expand Down
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