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Fix incorrect Py_XDECREF/Py_DECREF call on stolen reference after PyList_SetItem failure #885

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Fix incorrect Py_XDECREF/Py_DECREF call on stolen reference after PyList_SetItem failure #885

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3d920db
fix-RC
wr-web May 10, 2026
9c5d6ba
fix-RC and format
wr-web May 10, 2026
a735f27
fix-RC
wr-web May 10, 2026
72cebe4
fix-RC
wr-web May 10, 2026
455132b
fix-RC
wr-web May 10, 2026
a7b06cd
fix-RC
wr-web May 10, 2026
ed9161d
fix-RC
wr-web May 10, 2026
b91c9ce
fix-RC
wr-web May 10, 2026
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14 changes: 0 additions & 14 deletions src/_igraph/attributes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -282,7 +282,6 @@ PyObject* igraphmodule_i_create_edge_attribute(const igraph_t* graph,
Py_INCREF(Py_None);
if (PyList_SetItem(values, i, Py_None)) { /* reference stolen */
Py_DECREF(values);
Py_DECREF(Py_None);
return 0;
}
}
Expand Down Expand Up @@ -659,7 +658,6 @@ static igraph_error_t igraphmodule_i_attribute_add_vertices(

if (o) {
if (PyList_SetItem(value, i + j, o)) {
Py_DECREF(o); /* append failed */
o = NULL; /* indicate error */
} else {
/* reference stolen by the list */
Expand Down Expand Up @@ -721,7 +719,6 @@ static igraph_error_t igraphmodule_i_attribute_permute_vertices(const igraph_t *
Py_INCREF(o);
if (PyList_SetItem(newlist, i, o)) {
PyErr_PrintEx(0);
Py_DECREF(o);
Py_DECREF(newlist);
Py_DECREF(newdict);
IGRAPH_ERROR("", IGRAPH_FAILURE);
Expand Down Expand Up @@ -878,7 +875,6 @@ static igraph_error_t igraphmodule_i_attribute_add_edges(

if (o) {
if (PyList_SetItem(value, i + j, o)) {
Py_DECREF(o); /* append failed */
o = NULL; /* indicate error */
} else {
/* reference stolen by the list */
Expand Down Expand Up @@ -935,7 +931,6 @@ static igraph_error_t igraphmodule_i_attribute_permute_edges(const igraph_t *gra
Py_INCREF(o);
if (PyList_SetItem(newlist, i, o)) {
PyErr_PrintEx(0);
Py_DECREF(o);
Py_DECREF(newlist);
Py_DECREF(newdict);
IGRAPH_ERROR("", IGRAPH_FAILURE);
Expand Down Expand Up @@ -982,7 +977,6 @@ static PyObject* igraphmodule_i_ac_func(PyObject* values,
Py_INCREF(item);

if (PyList_SetItem(list, j, item)) { /* reference to item stolen */
Py_DECREF(item);
Py_DECREF(res);
return 0;
}
Expand Down Expand Up @@ -1070,7 +1064,6 @@ static PyObject* igraphmodule_i_ac_sum(PyObject* values,

item = PyFloat_FromDouble(sum);
if (PyList_SetItem(res, i, item)) { /* reference to item stolen */
Py_DECREF(item);
Py_DECREF(res);
return 0;
}
Expand Down Expand Up @@ -1114,7 +1107,6 @@ static PyObject* igraphmodule_i_ac_prod(PyObject* values,
/* reference to new float stolen */
item = PyFloat_FromDouble((double)prod);
if (PyList_SetItem(res, i, item)) { /* reference to item stolen */
Py_DECREF(item);
Py_DECREF(res);
return 0;
}
Expand Down Expand Up @@ -1147,7 +1139,6 @@ static PyObject* igraphmodule_i_ac_first(PyObject* values,

Py_INCREF(item);
if (PyList_SetItem(res, i, item)) { /* reference to item stolen */
Py_DECREF(item);
Py_DECREF(res);
return 0;
}
Expand Down Expand Up @@ -1207,7 +1198,6 @@ static PyObject* igraphmodule_i_ac_random(PyObject* values,

Py_INCREF(item);
if (PyList_SetItem(res, i, item)) { /* reference to item stolen */
Py_DECREF(item);
Py_DECREF(random_func);
Py_DECREF(res);
return 0;
Expand Down Expand Up @@ -1244,7 +1234,6 @@ static PyObject* igraphmodule_i_ac_last(PyObject* values,
Py_INCREF(item);

if (PyList_SetItem(res, i, item)) { /* reference to item stolen */
Py_DECREF(item);
Py_DECREF(res);
return 0;
}
Expand Down Expand Up @@ -1290,7 +1279,6 @@ static PyObject* igraphmodule_i_ac_mean(PyObject* values,
/* reference to new float stolen */
item = PyFloat_FromDouble((double)mean);
if (PyList_SetItem(res, i, item)) { /* reference to item stolen */
Py_DECREF(item);
Py_DECREF(res);
return 0;
}
Expand Down Expand Up @@ -1324,7 +1312,6 @@ static PyObject* igraphmodule_i_ac_median(PyObject* values,

Py_INCREF(item);
if (PyList_SetItem(list, j, item)) { /* reference to item stolen */
Py_DECREF(item);
Py_DECREF(list);
Py_DECREF(res);
return 0;
Expand Down Expand Up @@ -1383,7 +1370,6 @@ static PyObject* igraphmodule_i_ac_median(PyObject* values,

/* reference to item stolen */
if (PyList_SetItem(res, i, item)) {
Py_DECREF(item);
Py_DECREF(list);
Py_DECREF(res);
return 0;
Expand Down
3 changes: 0 additions & 3 deletions src/_igraph/edgeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -393,7 +393,6 @@ int igraphmodule_Edge_set_attribute(igraphmodule_EdgeObject* self, PyObject* k,
* It took me 1.5 hours between London and Manchester to figure it out */
Py_INCREF(v);
r=PyList_SetItem(result, self->idx, v);
if (r == -1) { Py_DECREF(v); }
return r;
}

Expand All @@ -406,15 +405,13 @@ int igraphmodule_Edge_set_attribute(igraphmodule_EdgeObject* self, PyObject* k,
if (i != self->idx) {
Py_INCREF(Py_None);
if (PyList_SetItem(result, i, Py_None) == -1) {
Py_DECREF(Py_None);
Py_DECREF(result);
return -1;
}
} else {
/* Same game with the reference count here */
Py_INCREF(v);
if (PyList_SetItem(result, i, v) == -1) {
Py_DECREF(v);
Py_DECREF(result);
return -1;
}
Expand Down
8 changes: 0 additions & 8 deletions src/_igraph/edgeseqobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -310,7 +310,6 @@ PyObject* igraphmodule_EdgeSeq_get_attribute_values(igraphmodule_EdgeSeqObject*
Py_INCREF(item);

if (PyList_SetItem(result, i, item)) {
Py_DECREF(item);
Py_DECREF(result);
return 0;
}
Expand All @@ -335,7 +334,6 @@ PyObject* igraphmodule_EdgeSeq_get_attribute_values(igraphmodule_EdgeSeqObject*
Py_INCREF(item);

if (PyList_SetItem(result, i, item)) {
Py_DECREF(item);
Py_DECREF(result);
return 0;
}
Expand All @@ -359,7 +357,6 @@ PyObject* igraphmodule_EdgeSeq_get_attribute_values(igraphmodule_EdgeSeqObject*
Py_INCREF(item);

if (PyList_SetItem(result, i, item)) {
Py_DECREF(item);
Py_DECREF(result);
return 0;
}
Expand Down Expand Up @@ -495,7 +492,6 @@ int igraphmodule_EdgeSeq_set_attribute_values_mapping(igraphmodule_EdgeSeqObject
}
/* No need to Py_INCREF(item), PySequence_GetItem returns a new reference */
if (PyList_SetItem(list, i, item)) {
Py_DECREF(item);
return -1;
} /* PyList_SetItem stole a reference to the item automatically */
}
Expand All @@ -516,7 +512,6 @@ int igraphmodule_EdgeSeq_set_attribute_values_mapping(igraphmodule_EdgeSeqObject
}
/* No need to Py_INCREF(item), PySequence_GetItem returns a new reference */
if (PyList_SetItem(list, i, item)) {
Py_DECREF(item);
Py_DECREF(list);
return -1;
}
Expand Down Expand Up @@ -560,7 +555,6 @@ int igraphmodule_EdgeSeq_set_attribute_values_mapping(igraphmodule_EdgeSeqObject
}
/* No need to Py_INCREF(item), PySequence_GetItem returns a new reference */
if (PyList_SetItem(list, VECTOR(es)[i], item)) {
Py_DECREF(item);
igraph_vector_int_destroy(&es);
return -1;
} /* PyList_SetItem stole a reference to the item automatically */
Expand All @@ -579,7 +573,6 @@ int igraphmodule_EdgeSeq_set_attribute_values_mapping(igraphmodule_EdgeSeqObject
for (i = 0; i < n2; i++) {
Py_INCREF(Py_None);
if (PyList_SetItem(list, i, Py_None)) {
Py_DECREF(Py_None);
Py_DECREF(list);
return -1;
}
Expand All @@ -596,7 +589,6 @@ int igraphmodule_EdgeSeq_set_attribute_values_mapping(igraphmodule_EdgeSeqObject
}
/* No need to Py_INCREF(item), PySequence_GetItem returns a new reference */
if (PyList_SetItem(list, VECTOR(es)[i], item)) {
Py_DECREF(item);
Py_DECREF(list);
return -1;
}
Expand Down
2 changes: 0 additions & 2 deletions src/_igraph/indexing.c
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Original file line number Diff line number Diff line change
Expand Up @@ -340,7 +340,6 @@ static int igraphmodule_i_Graph_adjmatrix_set_index_row(igraph_t* graph,
/* Setting attribute */
Py_INCREF(item);
if (PyList_SetItem(values, eid, item)) {
Py_DECREF(item);
igraph_vector_int_clear(&data->to_add);
}
}
Expand Down Expand Up @@ -402,7 +401,6 @@ static int igraphmodule_i_Graph_adjmatrix_set_index_row(igraph_t* graph,
/* Setting attribute */
Py_INCREF(new_value);
if (PyList_SetItem(values, eid, new_value)) {
Py_DECREF(new_value);
igraph_vector_int_clear(&data->to_add);
}
}
Expand Down
4 changes: 0 additions & 4 deletions src/_igraph/operators.c
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Original file line number Diff line number Diff line change
Expand Up @@ -156,7 +156,6 @@ PyObject *igraphmodule__union(PyObject *self,
if (!dest || PyList_SetItem(emi, j, dest)) {
igraph_vector_ptr_destroy(&gs);
igraph_vector_int_list_destroy(&edgemaps);
Py_XDECREF(dest);
Py_DECREF(emi);
Py_DECREF(em_list);
return NULL;
Expand All @@ -167,7 +166,6 @@ PyObject *igraphmodule__union(PyObject *self,
if (!emi || PyList_SetItem(em_list, i, emi)) {
igraph_vector_ptr_destroy(&gs);
igraph_vector_int_list_destroy(&edgemaps);
Py_XDECREF(emi);
Py_DECREF(em_list);
return NULL;
}
Expand Down Expand Up @@ -281,7 +279,6 @@ PyObject *igraphmodule__intersection(PyObject *self,
if (!dest || PyList_SetItem(emi, j, dest)) {
igraph_vector_ptr_destroy(&gs);
igraph_vector_int_list_destroy(&edgemaps);
Py_XDECREF(dest);
Py_DECREF(emi);
Py_DECREF(em_list);
return NULL;
Expand All @@ -292,7 +289,6 @@ PyObject *igraphmodule__intersection(PyObject *self,
if (!emi || PyList_SetItem(em_list, i, emi)) {
igraph_vector_ptr_destroy(&gs);
igraph_vector_int_list_destroy(&edgemaps);
Py_XDECREF(emi);
Py_DECREF(em_list);
return NULL;
}
Expand Down
7 changes: 3 additions & 4 deletions src/_igraph/pyhelpers.c
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Original file line number Diff line number Diff line change
Expand Up @@ -84,10 +84,9 @@ PyObject* igraphmodule_PyList_NewFill(Py_ssize_t len, PyObject* item) {
for (i = 0; i < len; i++) {
Py_INCREF(item);
if (PyList_SetItem(result, i, item)) {
Py_DECREF(item);
Py_DECREF(result);
return 0;
}
Py_DECREF(result);
return 0;
}
}

return result;
Expand Down
5 changes: 0 additions & 5 deletions src/_igraph/vertexobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -524,7 +524,6 @@ int igraphmodule_Vertex_set_attribute(igraphmodule_VertexObject* self, PyObject*
* It took me 1.5 hours between London and Manchester to figure it out */
Py_INCREF(v);
r=PyList_SetItem(result, self->idx, v);
if (r == -1) { Py_DECREF(v); }
return r;
}

Expand All @@ -537,15 +536,13 @@ int igraphmodule_Vertex_set_attribute(igraphmodule_VertexObject* self, PyObject*
if (i != self->idx) {
Py_INCREF(Py_None);
if (PyList_SetItem(result, i, Py_None) == -1) {
Py_DECREF(Py_None);
Py_DECREF(result);
return -1;
}
} else {
/* Same game with the reference count here */
Py_INCREF(v);
if (PyList_SetItem(result, i, v) == -1) {
Py_DECREF(v);
Py_DECREF(result);
return -1;
}
Expand Down Expand Up @@ -639,7 +636,6 @@ static PyObject* _convert_to_edge_list(igraphmodule_VertexObject* vertex, PyObje
}

if (PyList_SetItem(obj, i, edge)) { /* reference to v stolen, reference to idx discarded */
Py_DECREF(edge);
return NULL;
}
}
Expand Down Expand Up @@ -684,7 +680,6 @@ static PyObject* _convert_to_vertex_list(igraphmodule_VertexObject* vertex, PyOb
}

if (PyList_SetItem(obj, i, v)) { /* reference to v stolen, reference to idx discarded */
Py_DECREF(v);
return NULL;
}
}
Expand Down
8 changes: 0 additions & 8 deletions src/_igraph/vertexseqobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -295,7 +295,6 @@ PyObject* igraphmodule_VertexSeq_get_attribute_values(igraphmodule_VertexSeqObje
Py_INCREF(item);

if (PyList_SetItem(result, i, item)) {
Py_DECREF(item);
Py_DECREF(result);
return 0;
}
Expand All @@ -320,7 +319,6 @@ PyObject* igraphmodule_VertexSeq_get_attribute_values(igraphmodule_VertexSeqObje
Py_INCREF(item);

if (PyList_SetItem(result, i, item)) {
Py_DECREF(item);
Py_DECREF(result);
return 0;
}
Expand All @@ -343,7 +341,6 @@ PyObject* igraphmodule_VertexSeq_get_attribute_values(igraphmodule_VertexSeqObje
Py_INCREF(item);

if (PyList_SetItem(result, i, item)) {
Py_DECREF(item);
Py_DECREF(result);
return 0;
}
Expand Down Expand Up @@ -469,7 +466,6 @@ int igraphmodule_VertexSeq_set_attribute_values_mapping(igraphmodule_VertexSeqOb
if (item == 0) return -1;
/* No need to Py_INCREF(item), PySequence_GetItem returns a new reference */
if (PyList_SetItem(list, i, item)) {
Py_DECREF(item);
return -1;
} /* PyList_SetItem stole a reference to the item automatically */
}
Expand All @@ -487,7 +483,6 @@ int igraphmodule_VertexSeq_set_attribute_values_mapping(igraphmodule_VertexSeqOb
}
/* No need to Py_INCREF(item), PySequence_GetItem returns a new reference */
if (PyList_SetItem(list, i, item)) {
Py_DECREF(item);
Py_DECREF(list);
return -1;
}
Expand Down Expand Up @@ -530,7 +525,6 @@ int igraphmodule_VertexSeq_set_attribute_values_mapping(igraphmodule_VertexSeqOb
}
/* No need to Py_INCREF(item), PySequence_GetItem returns a new reference */
if (PyList_SetItem(list, VECTOR(vs)[i], item)) {
Py_DECREF(item);
igraph_vector_int_destroy(&vs);
return -1;
} /* PyList_SetItem stole a reference to the item automatically */
Expand All @@ -549,7 +543,6 @@ int igraphmodule_VertexSeq_set_attribute_values_mapping(igraphmodule_VertexSeqOb
for (i = 0; i < n2; i++) {
Py_INCREF(Py_None);
if (PyList_SetItem(list, i, Py_None)) {
Py_DECREF(Py_None);
Py_DECREF(list);
igraph_vector_int_destroy(&vs);
return -1;
Expand All @@ -566,7 +559,6 @@ int igraphmodule_VertexSeq_set_attribute_values_mapping(igraphmodule_VertexSeqOb
}
/* No need to Py_INCREF(item), PySequence_GetItem returns a new reference */
if (PyList_SetItem(list, VECTOR(vs)[i], item)) {
Py_DECREF(list);
Py_DECREF(item);
igraph_vector_int_destroy(&vs);
return -1;
Expand Down