2 files changed, 62 insertions, 0 deletions

diff --git a/Modules/_dbmmodule.c b/Modules/_dbmmodule.c
index 5913b03..9c83e38 100644
--- a/Modules/_dbmmodule.c
+++ b/Modules/_dbmmodule.c
@@ -130,6 +130,37 @@ dbm_length(dbmobject *dp)
     return dp->di_size;
 }
 
+static int
+dbm_bool(dbmobject *dp)
+{
+    _dbm_state *state = PyType_GetModuleState(Py_TYPE(dp));
+    assert(state != NULL);
+
+    if (dp->di_dbm == NULL) {
+        PyErr_SetString(state->dbm_error, "DBM object has already been closed");
+        return -1;
+    }
+
+    if (dp->di_size > 0) {
+        /* Known non-zero size. */
+        return 1;
+    }
+    if (dp->di_size == 0) {
+        /* Known zero size. */
+        return 0;
+    }
+
+    /* Unknown size.  Ensure DBM object has an entry. */
+    datum key = dbm_firstkey(dp->di_dbm);
+    if (key.dptr == NULL) {
+        /* Empty. Cache this fact. */
+        dp->di_size = 0;
+        return 0;
+    }
+    /* Non-empty. Don't cache the length since we don't know. */
+    return 1;
+}
+
 static PyObject *
 dbm_subscript(dbmobject *dp, PyObject *key)
 {
@@ -416,6 +447,7 @@ static PyType_Slot dbmtype_spec_slots[] = {
     {Py_mp_length, dbm_length},
     {Py_mp_subscript, dbm_subscript},
     {Py_mp_ass_subscript, dbm_ass_sub},
+    {Py_nb_bool, dbm_bool},
     {0, 0}
 };
 
diff --git a/Modules/_gdbmmodule.c b/Modules/_gdbmmodule.c
index e6440fa..a96d323 100644
--- a/Modules/_gdbmmodule.c
+++ b/Modules/_gdbmmodule.c
@@ -162,6 +162,35 @@ gdbm_length(gdbmobject *dp)
     return dp->di_size;
 }
 
+static int
+gdbm_bool(gdbmobject *dp)
+{
+    _gdbm_state *state = PyType_GetModuleState(Py_TYPE(dp));
+    if (dp->di_dbm == NULL) {
+        PyErr_SetString(state->gdbm_error, "GDBM object has already been closed");
+        return -1;
+    }
+    if (dp->di_size > 0) {
+        /* Known non-zero size. */
+        return 1;
+    }
+    if (dp->di_size == 0) {
+        /* Known zero size. */
+        return 0;
+    }
+    /* Unknown size.  Ensure DBM object has an entry. */
+    datum key = gdbm_firstkey(dp->di_dbm);
+    if (key.dptr == NULL) {
+        /* Empty. Cache this fact. */
+        dp->di_size = 0;
+        return 0;
+    }
+
+    /* Non-empty. Don't cache the length since we don't know. */
+    free(key.dptr);
+    return 1;
+}
+
 // Wrapper function for PyArg_Parse(o, "s#", &d.dptr, &d.size).
 // This function is needed to support PY_SSIZE_T_CLEAN.
 // Return 1 on success, same to PyArg_Parse().
@@ -569,6 +598,7 @@ static PyType_Slot gdbmtype_spec_slots[] = {
     {Py_mp_length, gdbm_length},
     {Py_mp_subscript, gdbm_subscript},
     {Py_mp_ass_subscript, gdbm_ass_sub},
+    {Py_nb_bool, gdbm_bool},
     {Py_tp_doc, (char*)gdbm_object__doc__},
     {0, 0}
 };