From: Andreas Schwab <schwab@linux-m68k.org>
Date: Mon, 29 Nov 2021 09:29:40 +0000 (+0100)
Subject: Avoid undefined behaviour when copying part of structure
X-Git-Tag: emacs-28.0.90~27
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=de9d27f679d5e040c0ed4b974bc9225f6a330852;p=emacs.git

Avoid undefined behaviour when copying part of structure

* src/dispnew.c (copy_row_except_pointers): Don't use address of
subobject as starting point.

(cherry picked from commit 6943786b5c1fe76ea05a3a810512bd6777883710)
---

diff --git a/src/dispnew.c b/src/dispnew.c
index 53eb8984747..4a9f2bae44b 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -1034,7 +1034,7 @@ copy_row_except_pointers (struct glyph_row *to, struct glyph_row *from)
 {
   enum { off = offsetof (struct glyph_row, x) };
 
-  memcpy (&to->x, &from->x, sizeof *to - off);
+  memcpy ((char *) to + off, (char *) from + off, sizeof *to - off);
 }