From 6ce8614f553d5efa70e25254d9cdb28a5dfa4d5f Mon Sep 17 00:00:00 2001 From: Sebastian Pipping Date: Wed, 6 Mar 2024 18:55:07 +0100 Subject: [PATCH] gh-115398: Revert `PyExpat_CAPI_MAGIC` version bump (GH-116411) Revert "gh-115398: Increment PyExpat_CAPI_MAGIC for SetReparseDeferralEnabled addition (GH-116301)" This reverts part of commit eda2963378a3c292cf6bb202bb00e94e46ee6d90. Why? this comment buried in an earlier code review explains: I checked again how that value is used in practice, it's here: https://github.com/python/cpython/blob/0c80da4c14d904a367968955544dd6ae58c8101c/Modules/_elementtree.c#L4363-L4372 Based on that code my understanding is that loading bigger structs from the future is considered okay unless `PyExpat_CAPI_MAGIC` differs, which implies that (1) magic needs to stay the same to support loading the future from the past and (2) that `PyExpat_CAPI_MAGIC` should only ever change for changes that do not increase size (but keep it constant). To summarize, that supports your argument. I checked branches 3.8, 3.9, 3.10, 3.11, 3.12 now and they all have the same comparison code there so reverting that magic string bump will support seamless backporting. --- Include/pyexpat.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Include/pyexpat.h b/Include/pyexpat.h index e0cff33b53227ae..9824d099c3df7d0 100644 --- a/Include/pyexpat.h +++ b/Include/pyexpat.h @@ -3,7 +3,7 @@ /* note: you must import expat.h before importing this module! */ -#define PyExpat_CAPI_MAGIC "pyexpat.expat_CAPI 1.2" +#define PyExpat_CAPI_MAGIC "pyexpat.expat_CAPI 1.1" #define PyExpat_CAPSULE_NAME "pyexpat.expat_CAPI" struct PyExpat_CAPI