bpo-40521: Always create the empty tuple singleton (GH-21116)

Py_InitializeFromConfig() now always creates the empty tuple
singleton as soon as possible.

Optimize PyTuple_New(0): it no longer has to check if the empty tuple
was created or not, it is always creatd.

* Add tuple_create_empty_tuple_singleton() function.
* Add tuple_get_empty() function.
* Remove state parameter of tuple_alloc().

1 files changed, 8 insertions, 1 deletions

diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index eda4c6a..4b658f8 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -583,6 +583,14 @@ pycore_init_types(PyThreadState *tstate)
         return status;
     }
 
+    // Create the empty tuple singleton. It must be created before the first
+    // PyType_Ready() call since PyType_Ready() creates tuples, for tp_bases
+    // for example.
+    status = _PyTuple_Init(tstate);
+    if (_PyStatus_EXCEPTION(status)) {
+        return status;
+    }
+
     if (is_main_interp) {
         status = _PyTypes_Init();
         if (_PyStatus_EXCEPTION(status)) {
@@ -590,7 +598,6 @@ pycore_init_types(PyThreadState *tstate)
         }
     }
 
-
     if (!_PyLong_Init(tstate)) {
         return _PyStatus_ERR("can't init longs");
     }