bpo-40521: Make bytes singletons per interpreter (GH-21074)

Each interpreter now has its own empty bytes string and single byte
character singletons.

Replace STRINGLIB_EMPTY macro with STRINGLIB_GET_EMPTY() macro.

1 files changed, 9 insertions, 5 deletions

diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-05-20-01-17-34.bpo-40521.wvAehI.rst b/Misc/NEWS.d/next/Core and Builtins/2020-05-20-01-17-34.bpo-40521.wvAehI.rst
index 24fd437..95fab36 100644
--- a/Misc/NEWS.d/next/Core and Builtins/2020-05-20-01-17-34.bpo-40521.wvAehI.rst
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-05-20-01-17-34.bpo-40521.wvAehI.rst
@@ -1,5 +1,9 @@
-The tuple free lists, the empty tuple singleton, the list free list, the empty
-frozenset singleton, the float free list, the slice cache, the dict free lists,
-the frame free list, the asynchronous generator free lists, and the context
-free list are no longer shared by all interpreters: each interpreter now its
-has own free lists and caches.
+Each interpreter now its has own free lists, singletons and caches:
+
+* Free lists: float, tuple, list, dict, frame, context,
+  asynchronous generator.
+* Singletons: empty tuple, empty frozenset, empty bytes string,
+  single byte character.
+* Slice cache.
+
+They are no longer shared by all interpreters.