From 588b3e5969a6992666c19fe390664efbb26ee8cf Mon Sep 17 00:00:00 2001
From: sobolevn <mail@sobolevn.me>
Date: Mon, 9 Oct 2023 12:24:15 +0300
Subject: [PATCH 1/4] gh-110525: Cover `PySet_Add` corner case with `frozenset`
 objects

---
 Modules/_testcapi/set.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/Modules/_testcapi/set.c b/Modules/_testcapi/set.c
index f68a1859698132..a0c6b6a605dc3a 100644
--- a/Modules/_testcapi/set.c
+++ b/Modules/_testcapi/set.c
@@ -129,6 +129,33 @@ set_clear(PyObject *self, PyObject *obj)
     RETURN_INT(PySet_Clear(obj));
 }
 
+static PyObject *
+test_frozenset_add_in_capi(PyObject *self, PyObject *Py_UNUSED(obj))
+{
+    // Test that `frozenset` can be used with `PySet_Add`,
+    // when frozenset is just created in CAPI.
+    PyObject *fs = PyFrozenSet_New(NULL);
+    if (fs == NULL) {
+        return NULL;
+    }
+    PyObject *num = PyLong_FromLong(1);
+    if (num == NULL) {
+        return NULL;
+    }
+    if (PySet_Add(fs, num) < 0) {
+        return NULL;
+    }
+    int contains = PySet_Contains(fs, num);
+    if (contains < 0) {
+        return NULL;
+    }
+    else if (contains == 0) {
+        PyErr_SetString(PyExc_ValueError, "set does not contain expected value");
+        return NULL;
+    }
+    Py_RETURN_NONE;
+}
+
 static PyMethodDef test_methods[] = {
     {"set_check", set_check, METH_O},
     {"set_checkexact", set_checkexact, METH_O},
@@ -148,6 +175,8 @@ static PyMethodDef test_methods[] = {
     {"set_pop", set_pop, METH_O},
     {"set_clear", set_clear, METH_O},
 
+    {"test_frozenset_add_in_capi", test_frozenset_add_in_capi, METH_NOARGS},
+
     {NULL},
 };
 

From 95f9ec759590660c69ed0430104d26a9e9d0b605 Mon Sep 17 00:00:00 2001
From: sobolevn <mail@sobolevn.me>
Date: Mon, 9 Oct 2023 13:13:39 +0300
Subject: [PATCH 2/4] Fix leak

---
 Modules/_testcapi/set.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Modules/_testcapi/set.c b/Modules/_testcapi/set.c
index a0c6b6a605dc3a..8cfdc65325a320 100644
--- a/Modules/_testcapi/set.c
+++ b/Modules/_testcapi/set.c
@@ -146,6 +146,7 @@ test_frozenset_add_in_capi(PyObject *self, PyObject *Py_UNUSED(obj))
         return NULL;
     }
     int contains = PySet_Contains(fs, num);
+    Py_DECREF(num);
     if (contains < 0) {
         return NULL;
     }

From 4235ee8879cdb1581f06c63c1929c52bcfcde913 Mon Sep 17 00:00:00 2001
From: sobolevn <mail@sobolevn.me>
Date: Mon, 9 Oct 2023 13:28:22 +0300
Subject: [PATCH 3/4] Longer version

---
 Modules/_testcapi/set.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/Modules/_testcapi/set.c b/Modules/_testcapi/set.c
index 8cfdc65325a320..4ba113f56b4cb1 100644
--- a/Modules/_testcapi/set.c
+++ b/Modules/_testcapi/set.c
@@ -140,21 +140,26 @@ test_frozenset_add_in_capi(PyObject *self, PyObject *Py_UNUSED(obj))
     }
     PyObject *num = PyLong_FromLong(1);
     if (num == NULL) {
-        return NULL;
+        goto error;
     }
     if (PySet_Add(fs, num) < 0) {
-        return NULL;
+        goto error;
     }
     int contains = PySet_Contains(fs, num);
-    Py_DECREF(num);
     if (contains < 0) {
-        return NULL;
+        goto error;
     }
     else if (contains == 0) {
-        PyErr_SetString(PyExc_ValueError, "set does not contain expected value");
-        return NULL;
+        goto unexpected;
     }
     Py_RETURN_NONE;
+
+unexpected:
+    PyErr_SetString(PyExc_ValueError, "set does not contain expected value");
+error:
+    Py_DECREF(fs);
+    Py_XDECREF(num);
+    return NULL;
 }
 
 static PyMethodDef test_methods[] = {

From 7d9ae7a6628428370781e86ff0149cbd2edb9065 Mon Sep 17 00:00:00 2001
From: sobolevn <mail@sobolevn.me>
Date: Mon, 9 Oct 2023 13:30:51 +0300
Subject: [PATCH 4/4] Longer version

---
 Modules/_testcapi/set.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Modules/_testcapi/set.c b/Modules/_testcapi/set.c
index 4ba113f56b4cb1..3c58f185638c75 100644
--- a/Modules/_testcapi/set.c
+++ b/Modules/_testcapi/set.c
@@ -152,6 +152,8 @@ test_frozenset_add_in_capi(PyObject *self, PyObject *Py_UNUSED(obj))
     else if (contains == 0) {
         goto unexpected;
     }
+    Py_DECREF(fs);
+    Py_DECREF(num);
     Py_RETURN_NONE;
 
 unexpected: