>From 556cc727e5076d590f8286406e4f46cff3cee41e Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Sun, 16 Feb 2020 11:36:19 -0800 Subject: [PATCH] Improve C-h C-h bug fix * src/lread.c (read1): Guard against two 'struct Lisp_Vector *' pointers differing only in their most significant bit. Problem reported by Pip Cet (Bug#39529#22). --- src/lread.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/src/lread.c b/src/lread.c index 1613719eb1..70984d37e1 100644 --- a/src/lread.c +++ b/src/lread.c @@ -2982,10 +2982,13 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list) as 0. This placeholder 0 would lead to accidental sharing in purecopy's hash-consing, so replace it with a (hopefully) unique integer placeholder, which is negative so that it is - not confused with a DOC file offset. Eventually - Snarf-documentation should replace the placeholder with the - actual docstring. */ - EMACS_UINT hash = XHASH (tmp) | (INTMASK - INTMASK / 2); + not confused with a DOC file offset (the USE_LSB_TAG shift + relies on the fact that VALMASK is one bit narrower than + INTMASK). Eventually Snarf-documentation should replace the + placeholder with the actual docstring. */ + verify (INTMASK & ~VALMASK); + EMACS_UINT hash = ((XHASH (tmp) >> USE_LSB_TAG) + | (INTMASK - INTMASK / 2)); ASET (tmp, COMPILED_DOC_STRING, make_ufixnum (hash)); } -- 2.17.1