bpo-38644: Make tstate more explicit inside pystate.c (GH-19182)
Fix PyInterpreterState_New(): Don't call PyErr_SetString() when there
is no current Python thread state (if tstate is NULL).
diff --git a/Doc/c-api/init.rst b/Doc/c-api/init.rst
index f78ab99..b5c647f 100644
--- a/Doc/c-api/init.rst
+++ b/Doc/c-api/init.rst
@@ -1119,6 +1119,8 @@
Return the interpreter's unique ID. If there was any error in doing
so then ``-1`` is returned and an error is set.
+ The caller must hold the GIL.
+
.. versionadded:: 3.7