From: Andreas Schwab <schwab@linux-m68k.org>
Date: Sun, 12 Aug 2018 09:03:36 +0000 (+0200)
Subject: Avoid padding after union vectorlike_header
X-Git-Tag: emacs-27.0.90~4589
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=3d0a0ca7ca58cdb8f07be63df28ad30e4367167d;p=emacs.git

Avoid padding after union vectorlike_header

The PSEUDOVECTORSIZE macro requires that the first member after union
vectorlike_header has the same offset in all pseudo vector structures.

* src/lisp.h (GCALIGNMENT) [!USE_LSB_TAG]: Use alignment of
Lisp_Object.
---

diff --git a/src/lisp.h b/src/lisp.h
index dcc157e0b96..96256386218 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -276,15 +276,17 @@ error !;
 
 /* Minimum alignment requirement for Lisp objects, imposed by the
    internal representation of tagged pointers.  It is 2**GCTYPEBITS if
-   USE_LSB_TAG, 1 otherwise.  It must be a literal integer constant,
-   for older versions of GCC (through at least 4.9).  */
+   USE_LSB_TAG, otherwise the alignment of Lisp_Object to avoid
+   padding after union vectorlike_header.  It must be a literal
+   integer constant, for older versions of GCC (through at least
+   4.9).  */
 #if USE_LSB_TAG
 # define GCALIGNMENT 8
 # if GCALIGNMENT != 1 << GCTYPEBITS
 #  error "GCALIGNMENT and GCTYPEBITS are inconsistent"
 # endif
 #else
-# define GCALIGNMENT 1
+# define GCALIGNMENT alignof (Lisp_Object)
 #endif
 
 #define GCALIGNED_UNION char alignas (GCALIGNMENT) gcaligned;