bpo-42412: Fix possible leaks and check arguments in PyType_FromModuleAndSpec() (GH-23410)

* There were leaks if Py_tp_bases is used more than once or if some call is
  failed before setting tp_bases.
* There was a crash if the bases argument or the Py_tp_bases slot is not a tuple.
* The documentation was not accurate.

1 files changed, 4 insertions, 2 deletions

diff --git a/Doc/c-api/type.rst b/Doc/c-api/type.rst
index 84c0a02..a822b67 100644
--- a/Doc/c-api/type.rst
+++ b/Doc/c-api/type.rst
@@ -157,7 +157,8 @@ The following functions and structs are used to create
    If *bases* is a tuple, the created heap type contains all types contained
    in it as base types.
 
-   If *bases* is ``NULL``, the *Py_tp_base* slot is used instead.
+   If *bases* is ``NULL``, the *Py_tp_bases* slot is used instead.
+   If that also is ``NULL``, the *Py_tp_base* slot is used instead.
    If that also is ``NULL``, the new type derives from :class:`object`.
 
    The *module* argument can be used to record the module in which the new
@@ -253,7 +254,8 @@ The following functions and structs are used to create
       * :c:member:`~PyBufferProcs.bf_getbuffer`
       * :c:member:`~PyBufferProcs.bf_releasebuffer`
 
-      Setting :c:data:`Py_tp_bases` may be problematic on some platforms.
+      Setting :c:data:`Py_tp_bases` or :c:data:`Py_tp_base` may be
+      problematic on some platforms.
       To avoid issues, use the *bases* argument of
       :py:func:`PyType_FromSpecWithBases` instead.