gh-87193: Support bytes objects with refcount > 1 in _PyBytes_Resize() (GH-117160)

Create a new bytes object and destroy the old one if it has refcount > 1.

Modules/Setup.stdlib.in

@@ -162,7 +162,7 @@
 @MODULE__XXTESTFUZZ_TRUE@_xxtestfuzz _xxtestfuzz/_xxtestfuzz.c _xxtestfuzz/fuzzer.c
 @MODULE__TESTBUFFER_TRUE@_testbuffer _testbuffer.c
 @MODULE__TESTINTERNALCAPI_TRUE@_testinternalcapi _testinternalcapi.c _testinternalcapi/test_lock.c _testinternalcapi/pytime.c _testinternalcapi/set.c _testinternalcapi/test_critical_sections.c
-@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c
+@MODULE__TESTCAPI_TRUE@_testcapi _testcapimodule.c _testcapi/vectorcall.c _testcapi/heaptype.c _testcapi/abstract.c _testcapi/unicode.c _testcapi/dict.c _testcapi/set.c _testcapi/list.c _testcapi/tuple.c _testcapi/getargs.c _testcapi/datetime.c _testcapi/docstring.c _testcapi/mem.c _testcapi/watchers.c _testcapi/long.c _testcapi/float.c _testcapi/complex.c _testcapi/numbers.c _testcapi/structmember.c _testcapi/exceptions.c _testcapi/code.c _testcapi/buffer.c _testcapi/pyatomic.c _testcapi/file.c _testcapi/codec.c _testcapi/immortal.c _testcapi/gc.c _testcapi/hash.c _testcapi/time.c _testcapi/bytes.c
 @MODULE__TESTLIMITEDCAPI_TRUE@_testlimitedcapi _testlimitedcapi.c _testlimitedcapi/abstract.c _testlimitedcapi/bytearray.c _testlimitedcapi/bytes.c _testlimitedcapi/complex.c _testlimitedcapi/dict.c _testlimitedcapi/float.c _testlimitedcapi/heaptype_relative.c _testlimitedcapi/list.c _testlimitedcapi/long.c _testlimitedcapi/object.c _testlimitedcapi/pyos.c _testlimitedcapi/set.c _testlimitedcapi/sys.c _testlimitedcapi/unicode.c _testlimitedcapi/vectorcall_limited.c
 @MODULE__TESTCLINIC_TRUE@_testclinic _testclinic.c
 @MODULE__TESTCLINIC_LIMITED_TRUE@_testclinic_limited _testclinic_limited.c

Modules/_testcapi/bytes.c

@@ -0,0 +1,53 @@
+#include "parts.h"
+#include "util.h"
+
+
+/* Test _PyBytes_Resize() */
+static PyObject *
+bytes_resize(PyObject *Py_UNUSED(module), PyObject *args)
+{
+    PyObject *obj;
+    Py_ssize_t newsize;
+    int new;
+
+    if (!PyArg_ParseTuple(args, "Onp", &obj, &newsize, &new))
+        return NULL;
+
+    NULLABLE(obj);
+    if (new) {
+        assert(obj != NULL);
+        assert(PyBytes_CheckExact(obj));
+        PyObject *newobj = PyBytes_FromStringAndSize(NULL, PyBytes_Size(obj));
+        if (newobj == NULL) {
+            return NULL;
+        }
+        memcpy(PyBytes_AsString(newobj), PyBytes_AsString(obj), PyBytes_Size(obj));
+        obj = newobj;
+    }
+    else {
+        Py_XINCREF(obj);
+    }
+    if (_PyBytes_Resize(&obj, newsize) < 0) {
+        assert(obj == NULL);
+    }
+    else {
+        assert(obj != NULL);
+    }
+    return obj;
+}
+
+
+static PyMethodDef test_methods[] = {
+    {"bytes_resize", bytes_resize, METH_VARARGS},
+    {NULL},
+};
+
+int
+_PyTestCapi_Init_Bytes(PyObject *m)
+{
+    if (PyModule_AddFunctions(m, test_methods) < 0) {
+        return -1;
+    }
+
+    return 0;
+}

Modules/_testcapi/parts.h

@@ -31,6 +31,7 @@
 int _PyTestCapi_Init_Vectorcall(PyObject *module);
 int _PyTestCapi_Init_Heaptype(PyObject *module);
 int _PyTestCapi_Init_Abstract(PyObject *module);
+int _PyTestCapi_Init_Bytes(PyObject *module);
 int _PyTestCapi_Init_Unicode(PyObject *module);
 int _PyTestCapi_Init_GetArgs(PyObject *module);
 int _PyTestCapi_Init_DateTime(PyObject *module);

Modules/_testcapimodule.c

@@ -3971,6 +3971,9 @@ PyInit__testcapi(void)
     if (_PyTestCapi_Init_Abstract(m) < 0) {
         return NULL;
     }
+    if (_PyTestCapi_Init_Bytes(m) < 0) {
+        return NULL;
+    }
     if (_PyTestCapi_Init_Unicode(m) < 0) {
         return NULL;
     }