Subject: bug#9772: <stdalign.h>, USE_LSB_TAG, and MSVC

From: Paul Eggert <[email-masked]>
Date: Sun, 16 Oct 2011 20:24:31 -0700

Package: Emacs
Version: 24.0.90
Tags: patch

Here's a patch to the Emacs trunk (bzr 106094) to cause it to use
<stdalign.h> if available, falling back on a Gnulib replacement
otherwise.  This simplifies Emacs proper, and should future-proof it
for C1X compilers.

Although this patch is mostly just a cleanup patch for GNU and POSIX
platforms, it may improve performance on some Microsoft hosts, as it
contains code for supporting <stdalign.h> under MSVC.  As far as I can
see, USE_LSB_TAG currently doesn't work with MSVC, so if this patch
works it should increase the maximum Emacs buffer size in that
environment.  I haven't tested it under Windows, though, and quite
possibly further work will be needed in that area.

Since this is Microsoft-build relevant, I'll CC: this bug report to Eli.

=== modified file '.bzrignore'
--- .bzrignore	2011-09-29 14:19:11 +0000
+++ .bzrignore	2011-10-17 01:22:19 +0000
@@ -53,6 +53,7 @@
 lib/c++defs.h
 lib/getopt.h
 lib/inttypes.h
+lib/stdalign.h
 lib/stdbool.h
 lib/stdio.h
 lib/stdint.h

=== modified file 'ChangeLog'
--- ChangeLog	2011-10-13 02:16:59 +0000
+++ ChangeLog	2011-10-17 01:22:19 +0000
@@ -1,3 +1,18 @@
+2011-10-17  Paul Eggert  <[email-masked]>
+
+	Use Gnulib stdalign module.
+	This should improve portability of macros like alignof and DECL_ALIGN.
+	* lib/stdalign.in.h, m4/stdalign.m4: New files, from gnulib.
+	* .bzrignore: Add lib/stdalign.h.
+	* Makefile.in (GNULIB_MODULES): Add stdalign.
+	* config.bat: Set HAVE_ATTRIBUTE_ALIGNED in lib/stdalign.h,
+	instead of NO_DECL_ALIGN in config.h.  Copy lib/stdalign.in.h to
+	lib/stdalign.in-h as needed.
+	* configure.in (HAVE_ATTRIBUTE_ALIGNED): Remove the code that
+	fiddles with this, as gnulib now does this for us.
+	* lib/gnulib.mk, lib/md5.c, lib/sha1.c, lib/sha256.c, lib/sha512.c:
+	* m4/gl-comp.m4, m4/pthread_sigmask.m4: Merge from gnulib.
+
 2011-10-13  Glenn Morris  <[email-masked]>
 
 	* configure.in: Also look for tputs in libcurses.  (Bug#9736)

=== modified file 'Makefile.in'
--- Makefile.in	2011-09-26 21:30:18 +0000
+++ Makefile.in	2011-10-17 01:22:19 +0000
@@ -337,7 +337,7 @@
   dup2 \
   filemode getloadavg getopt-gnu ignore-value intprops lstat \
   mktime pthread_sigmask readlink \
-  socklen stdarg stdio strftime strtoimax strtoumax symlink sys_stat
+  socklen stdalign stdarg stdio strftime strtoimax strtoumax symlink sys_stat
 GNULIB_TOOL_FLAGS = \
  --avoid=msvc-inval --avoid=msvc-nothrow --avoid=pathmax \
  --avoid=raise --avoid=threadlib \

=== modified file 'config.bat'
--- config.bat	2011-09-29 12:08:36 +0000
+++ config.bat	2011-10-17 01:22:19 +0000
@@ -161,7 +161,8 @@
 sed -f ../msdos/sed2x.inp < ..\autogen\config.in > config.tmp

 :src4

 sed -f ../msdos/sed2v2.inp <config.tmp >config.h2

-Rem See if DECL_ALIGN can be supported with this GCC

+Rem See if alignas can be supported with this GCC

+set HAVE_ATTRIBUTE_ALIGNED=1

 rm -f junk.c junk.o junk junk.exe

 echo struct { int i; char *p; } __attribute__((__aligned__(8))) foo;  >junk.c

 rem Two percent signs because it is a special character for COMMAND.COM/CMD

@@ -173,9 +174,9 @@
 If Not ErrorLevel 1 Goto alignOk

 Echo WARNING: Your GCC does not support 8-byte aligned variables.

 Echo WARNING: Therefore Emacs cannot support buffers larger than 128MB.

-rem The following line disables DECL_ALIGN which in turn disables USE_LSB_TAG

+rem The following line disables alignas which in turn disables USE_LSB_TAG

 rem For details see lisp.h where it defines USE_LSB_TAG

-echo #define NO_DECL_ALIGN >>config.h2

+set HAVE_ATTRIBUTE_ALIGNED=0

 :alignOk

 Rem See if they have libxml2 later than v2.2.0 installed

 Echo Checking whether libxml2 v2.2.1 or later is installed ...

@@ -281,6 +282,7 @@
 If Exist build-aux\snippet\c++defs.h update build-aux/snippet/c++defs.h build-aux/snippet/cxxdefs.h

 If Exist alloca.in.h update alloca.in.h alloca.in-h

 If Exist getopt.in.h update getopt.in.h getopt.in-h

+If Exist stdalign.in.h update stdalign.in.h stdalign.in-h

 If Exist stdbool.in.h update stdbool.in.h stdbool.in-h

 If Exist signal.in.h update signal.in.h signal.in-h

 If Exist stddef.in.h update stddef.in.h  stddef.in-h

@@ -290,7 +292,7 @@
 If Exist sys_stat.in.h update sys_stat.in.h sys_stat.in-h

 If Exist time.in.h update time.in.h time.in-h

 If Exist unistd.in.h update unistd.in.h unistd.in-h

-sed -f ../msdos/sedlibcf.inp < ..\autogen\Makefile.in > makefile.tmp

+sed -e "s/@HAVE_ATTRIBUTE_ALIGNED@/%HAVE_ATTRIBUTE_ALIGNED%/g" -f ../msdos/sedlibcf.inp < ..\autogen\Makefile.in > makefile.tmp

 sed -f ../msdos/sedlibmk.inp < makefile.tmp > Makefile

 rm -f makefile.tmp

 Rem Create .Po files for new files in lib/

@@ -343,4 +345,3 @@
 set djgpp_ver=

 set sys_malloc=

 set libxml=

-

=== modified file 'configure.in'
--- configure.in	2011-10-13 02:16:59 +0000
+++ configure.in	2011-10-17 01:22:19 +0000
@@ -1357,19 +1357,6 @@
 dnl Check for endianess
 AC_C_BIGENDIAN
 
-AC_CACHE_CHECK([for  __attribute__ ((__aligned__ (expr)))],
-  [emacs_cv_attribute_aligned],
-  [AC_COMPILE_IFELSE(
-     [AC_LANG_PROGRAM(
-	[[char __attribute__ ((__aligned__ (1 << 3))) c;]],
-	[[]])],
-     [emacs_cv_attribute_aligned=yes],
-     [emacs_cv_attribute_aligned=no])])
-if test $emacs_cv_attribute_aligned = yes; then
-  AC_DEFINE([HAVE_ATTRIBUTE_ALIGNED], 1,
-    [Define to 1 if GCC-style __attribute__ ((__aligned__ (expr))) works.])
-fi
-
 dnl check for Make feature
 AC_PROG_MAKE_SET

=== modified file 'lib/gnulib.mk'
--- lib/gnulib.mk	2011-09-26 21:30:18 +0000
+++ lib/gnulib.mk	2011-10-17 01:22:19 +0000
@@ -21,7 +21,7 @@
 # the same distribution terms as the rest of that program.
 #
 # Generated by gnulib-tool.
-# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=msvc-inval --avoid=msvc-nothrow --avoid=pathmax --avoid=raise --avoid=threadlib --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt careadlinkat crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dup2 filemode getloadavg getopt-gnu ignore-value intprops lstat mktime pthread_sigmask readlink socklen stdarg stdio strftime strtoimax strtoumax symlink sys_stat
+# Reproduce by: gnulib-tool --import --dir=. --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=msvc-inval --avoid=msvc-nothrow --avoid=pathmax --avoid=raise --avoid=threadlib --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt careadlinkat crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dup2 filemode getloadavg getopt-gnu ignore-value intprops lstat mktime pthread_sigmask readlink socklen stdalign stdarg stdio strftime strtoimax strtoumax symlink sys_stat

 MOSTLYCLEANFILES += core *.stackdump
@@ -421,6 +421,29 @@
 
 ## end   gnulib module stat
 
+## begin gnulib module stdalign
+
+BUILT_SOURCES += $(STDALIGN_H)
+
+# We need the following in order to create <stdalign.h> when the system
+# doesn't have one that works.
+if GL_GENERATE_STDALIGN_H
+stdalign.h: stdalign.in.h $(top_builddir)/config.status
+	$(AM_V_GEN)rm -f $@-t $@ && \
+	{ echo '/* DO NOT EDIT! GENERATED AUTOMATICALLY! */'; \
+	  sed -e 's/@''HAVE_ATTRIBUTE_ALIGNED''@/$(HAVE_ATTRIBUTE_ALIGNED)/g' < $(srcdir)/stdalign.in.h; \
+	} > $@-t && \
+	mv $@-t $@
+else
+stdalign.h: $(top_builddir)/config.status
+	rm -f $@
+endif
+MOSTLYCLEANFILES += stdalign.h stdalign.h-t
+
+EXTRA_DIST += stdalign.in.h
+
+## end   gnulib module stdalign
+
 ## begin gnulib module stdarg
 
 BUILT_SOURCES += $(STDARG_H)

=== modified file 'lib/md5.c'
--- lib/md5.c	2011-02-19 07:28:29 +0000
+++ lib/md5.c	2011-10-17 01:22:19 +0000
@@ -24,7 +24,8 @@
 
 #include "md5.h"
 
-#include <stddef.h>
+#include <stdalign.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
@@ -254,8 +255,7 @@
   if (len >= 64)
     {
 #if !_STRING_ARCH_unaligned
-# define alignof(type) offsetof (struct { char c; type x; }, x)
-# define UNALIGNED_P(p) (((size_t) p) % alignof (uint32_t) != 0)
+# define UNALIGNED_P(p) ((uintptr_t) (p) % alignof (uint32_t) != 0)
       if (UNALIGNED_P (buffer))
         while (len > 64)
           {

=== modified file 'lib/sha1.c'
--- lib/sha1.c	2011-05-24 08:12:52 +0000
+++ lib/sha1.c	2011-10-17 01:22:19 +0000
@@ -26,7 +26,8 @@
 
 #include "sha1.h"
 
-#include <stddef.h>
+#include <stdalign.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -241,8 +242,7 @@
   if (len >= 64)
     {
 #if !_STRING_ARCH_unaligned
-# define alignof(type) offsetof (struct { char c; type x; }, x)
-# define UNALIGNED_P(p) (((size_t) p) % alignof (uint32_t) != 0)
+# define UNALIGNED_P(p) ((uintptr_t) (p) % alignof (uint32_t) != 0)
       if (UNALIGNED_P (buffer))
         while (len > 64)
           {

=== modified file 'lib/sha256.c'
--- lib/sha256.c	2011-06-21 08:45:39 +0000
+++ lib/sha256.c	2011-10-17 01:22:19 +0000
@@ -24,7 +24,8 @@
 
 #include "sha256.h"
 
-#include <stddef.h>
+#include <stdalign.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -373,8 +374,7 @@
   if (len >= 64)
     {
 #if !_STRING_ARCH_unaligned
-# define alignof(type) offsetof (struct { char c; type x; }, x)
-# define UNALIGNED_P(p) (((size_t) p) % alignof (uint32_t) != 0)
+# define UNALIGNED_P(p) ((uintptr_t) (p) % alignof (uint32_t) != 0)
       if (UNALIGNED_P (buffer))
         while (len > 64)
           {

=== modified file 'lib/sha512.c'
--- lib/sha512.c	2011-06-21 08:45:39 +0000
+++ lib/sha512.c	2011-10-17 01:22:19 +0000
@@ -24,7 +24,8 @@
 
 #include "sha512.h"
 
-#include <stddef.h>
+#include <stdalign.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -381,8 +382,7 @@
   if (len >= 128)
     {
 #if !_STRING_ARCH_unaligned
-# define alignof(type) offsetof (struct { char c; type x; }, x)
-# define UNALIGNED_P(p) (((size_t) p) % alignof (u64) != 0)
+# define UNALIGNED_P(p) ((uintptr_t) (p) % alignof (u64) != 0)
       if (UNALIGNED_P (buffer))
         while (len > 128)
           {

=== added file 'lib/stdalign.in.h'
--- lib/stdalign.in.h	1970-01-01 00:00:00 +0000
+++ lib/stdalign.in.h	2011-10-17 01:22:19 +0000
@@ -0,0 +1,61 @@
+/* A substitute for ISO C 1x <stdalign.h>.
+
+   Copyright 2011 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by Paul Eggert and Bruno Haible.  */
+
+#ifndef _GL_STDALIGN_H
+#define _GL_STDALIGN_H
+
+/* ISO C1X <stdalign.h> for platforms that lack it.
+
+   References:
+   ISO C1X <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf>
+   sections 6.5.3.4, 6.7.5, 7.15.
+   C++0X <http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf>
+   section 18.10. */
+
+/* Return the alignment of a structure slot (field) of TYPE,
+   as an integer constant expression.  The result cannot be used as a
+   value for an 'enum' constant, if you want to be portable to HP-UX
+   10.20 cc and AIX 3.2.5 xlc.
+
+   This is not the same as GCC's __alignof__ operator; for example, on
+   x86 with GCC, _Alignof (long long) is typically 4 whereas
+   __alignof__ (long long) is 8.  */
+#include <stddef.h>
+#if defined __cplusplus
+   template <class __t> struct __alignof_helper { char __a; __t __b; };
+# define _Alignof(type) offsetof (__alignof_helper<type>, __b)
+#else
+# define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
+#endif
+#define alignof _Alignof
+#define __alignof_is_defined 1
+
+/* Align a type or variable to the alignment A.  */
+#if @HAVE_ATTRIBUTE_ALIGNED@ && !defined __cplusplus
+# define _Alignas(a) __attribute__ ((__aligned__ (a)))
+#elif 1300 <= _MSC_VER
+# define _Alignas(a) __declspec ((align (a)))
+#endif
+#ifdef _Alignas
+# define alignas _Alignas
+# define __alignas_is_defined 1
+#endif
+
+#endif /* _GL_STDALIGN_H */

=== modified file 'm4/gl-comp.m4'
--- m4/gl-comp.m4	2011-10-07 21:15:00 +0000
+++ m4/gl-comp.m4	2011-10-17 01:22:19 +0000
@@ -76,6 +76,7 @@
   # Code from module socklen:
   # Code from module ssize_t:
   # Code from module stat:
+  # Code from module stdalign:
   # Code from module stdarg:
   dnl Some compilers (e.g., AIX 5.3 cc) need to be in c99 mode
   dnl for the builtin va_copy to work.  With Autoconf 2.60 or later,
@@ -180,6 +181,7 @@
 gl_SIGNAL_H
 gl_TYPE_SOCKLEN_T
 gt_TYPE_SSIZE_T
+gl_STDALIGN_H
 gl_STDARG_H
 AM_STDBOOL_H
 gl_STDDEF_H
@@ -311,18 +313,18 @@
   if test $HAVE_READLINK = 0 || test $REPLACE_READLINK = 1; then
     func_gl_gnulib_m4code_stat
   fi
-  if test $ac_cv_func_strtoimax = no; then
-    func_gl_gnulib_m4code_verify
-  fi
   if test $ac_cv_func_strtoimax = no && test $ac_cv_type_long_long_int = yes; then
     func_gl_gnulib_m4code_strtoll
   fi
-  if test $ac_cv_func_strtoumax = no; then
+  if test $ac_cv_func_strtoimax = no; then
     func_gl_gnulib_m4code_verify
   fi
   if test $ac_cv_func_strtoumax = no && test $ac_cv_type_unsigned_long_long_int = yes; then
     func_gl_gnulib_m4code_strtoull
   fi
+  if test $ac_cv_func_strtoumax = no; then
+    func_gl_gnulib_m4code_verify
+  fi
   m4_pattern_allow([^gl_GNULIB_ENABLED_])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_dosname], [$gl_gnulib_enabled_dosname])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_be453cec5eecf5731a274f2de7f2db36], [$gl_gnulib_enabled_be453cec5eecf5731a274f2de7f2db36])
@@ -513,6 +515,7 @@
   lib/signal.in.h
   lib/sigprocmask.c
   lib/stat.c
+  lib/stdalign.in.h
   lib/stdarg.in.h
   lib/stdbool.in.h
   lib/stddef.in.h
@@ -563,6 +566,7 @@
   m4/ssize_t.m4
   m4/st_dm_mode.m4
   m4/stat.m4
+  m4/stdalign.m4
   m4/stdarg.m4
   m4/stdbool.m4
   m4/stddef_h.m4

=== modified file 'm4/pthread_sigmask.m4'
--- m4/pthread_sigmask.m4	2011-09-03 23:08:32 +0000
+++ m4/pthread_sigmask.m4	2011-10-17 01:22:19 +0000
@@ -1,4 +1,4 @@
-# pthread_sigmask.m4 serial 12
+# pthread_sigmask.m4 serial 13
 dnl Copyright (C) 2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,6 +6,8 @@
 
 AC_DEFUN([gl_FUNC_PTHREAD_SIGMASK],
 [
+  AC_REQUIRE([gl_SIGNAL_H_DEFAULTS])
+
   AC_CHECK_FUNCS_ONCE([pthread_sigmask])
   LIB_PTHREAD_SIGMASK=

=== added file 'm4/stdalign.m4'
--- m4/stdalign.m4	1970-01-01 00:00:00 +0000
+++ m4/stdalign.m4	2011-10-17 01:22:19 +0000
@@ -0,0 +1,37 @@
+# Check for stdalign.h that conforms to C1x.
+
+dnl Copyright 2011 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+# Prepare for substituting <stdalign.h> if it is not supported.
+
+AC_DEFUN([gl_STDALIGN_H],
+[
+  AC_CHECK_HEADERS_ONCE([stdalign.h])
+  HAVE_ATTRIBUTE_ALIGNED='?'
+
+  if test "$ac_cv_header_stdalign_h" = yes; then
+    STDALIGN_H=''
+  else
+    STDALIGN_H='stdalign.h'
+    AC_CACHE_CHECK([for  __attribute__ ((__aligned__ (expr)))],
+      [gl_cv_attribute_aligned],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM(
+            [[char __attribute__ ((__aligned__ (1 << 3))) c;]],
+            [[]])],
+         [gl_cv_attribute_aligned=yes],
+         [gl_cv_attribute_aligned=no])])
+    if test $gl_cv_attribute_aligned = yes; then
+      HAVE_ATTRIBUTE_ALIGNED=1
+    else
+      HAVE_ATTRIBUTE_ALIGNED=0
+    fi
+  fi
+
+  AC_SUBST([HAVE_ATTRIBUTE_ALIGNED])
+  AC_SUBST([STDALIGN_H])
+  AM_CONDITIONAL([GL_GENERATE_STDALIGN_H], [test -n "$STDALIGN_H"])
+])

=== modified file 'msdos/ChangeLog'
--- msdos/ChangeLog	2011-09-29 12:00:18 +0000
+++ msdos/ChangeLog	2011-10-17 01:22:19 +0000
@@ -1,3 +1,10 @@
+2011-10-17  Paul Eggert  <[email-masked]>
+
+	Use Gnulib stdalign module.
+	* sed2v2.inp (HAVE_ATTRIBUTE_ALIGNED): Remove edit.
+	* sedlibmk.inp (STDALIGN_H, @GL_GENERATE_STDALIGN_H_TRUE@)
+	(GL_GENERATE_STDALIGN_H_FALSE): New edits.
+
 2011-09-29  Eli Zaretskii  <[email-masked]>
 
 	* mainmake.v2 (boot): Condition the value on the existence of

=== modified file 'msdos/sed2v2.inp'
--- msdos/sed2v2.inp	2011-09-29 12:00:18 +0000
+++ msdos/sed2v2.inp	2011-10-17 01:22:19 +0000
@@ -35,7 +35,6 @@
 /^#undef HAVE_FREXP *$/s/^.*$/#define HAVE_FREXP 1/
 /^#undef HAVE_FMOD *$/s/^.*$/#define HAVE_FMOD 1/
 /^#undef HAVE_RINT *$/s/^.*$/#define HAVE_RINT 1/
-/^#undef HAVE_ATTRIBUTE_ALIGNED *$/s/^.*$/#define HAVE_ATTRIBUTE_ALIGNED 1/
 /^#undef HAVE_C99_STRTOLD *$/s/^.*$/#define HAVE_C99_STRTOLD 1/
 /^#undef HAVE_CBRT *$/s/^.*$/#define HAVE_CBRT 1/
 /^#undef HAVE_DIFFTIME *$/s/^.*$/#define HAVE_DIFFTIME 1/
@@ -119,4 +118,3 @@
 # might be defined in sys/config.h we include at the top of config.h.
 /^#undef BSTRING/s|#undef|# undef|
 /^#undef .*$/s|^.*$|/* & */|
-

=== modified file 'msdos/sedlibmk.inp'
--- msdos/sedlibmk.inp	2011-09-29 12:00:18 +0000
+++ msdos/sedlibmk.inp	2011-10-17 01:22:19 +0000
@@ -27,7 +27,7 @@
 #    otherwise edit them to zero:
 #
 #     /^REPLACE_CALLOC *=/s/@REPLACE_CALLOC@/0/
-# 
+#
 #  . If the module is a header or adds headers, edit the corresponding
 #    variable to either an empty value or to the name of the header.
 #    Examples:
@@ -547,6 +547,7 @@
 /^SIZE_T_SUFFIX *=/s/@SIZE_T_SUFFIX@/u/
 /^ALLOCA_H *=/s/@[^@\n]*@/alloca.h/
 /^STDBOOL_H *=/s/@[^@\n]*@//
+/^STDALIGN_H *=/s/@[^@\n]*@/stdalign.h/
 /^STDARG_H *=/s/@[^@\n]*@//
 /^STDDEF_H *=/s/@[^@\n]*@//
 /^STDINT_H *=/s/@[^@\n]*@/stdint.h/
@@ -600,6 +601,8 @@
 s/^@GL_GENERATE_ALLOCA_H_FALSE@/\#/
 s/^@GL_GENERATE_STDBOOL_H_TRUE@/\#/
 s/^@GL_GENERATE_STDBOOL_H_FALSE@//
+s/^@GL_GENERATE_STDALIGN_H_TRUE@//
+s/^@GL_GENERATE_STDALIGN_H_FALSE@/\#/
 s/^@GL_GENERATE_STDARG_H_TRUE@/\#/
 s/^@GL_GENERATE_STDARG_H_FALSE@/\#/
 s/^@GL_GENERATE_STDDEF_H_TRUE@/\#/

=== modified file 'nt/ChangeLog'
--- nt/ChangeLog	2011-09-04 21:52:59 +0000
+++ nt/ChangeLog	2011-10-17 01:22:19 +0000
@@ -1,3 +1,8 @@
+2011-10-17  Paul Eggert  <[email-masked]>
+
+	Use Gnulib stdalign module.
+	* config.nt (HAVE_ATTRIBUTE_ALIGNED): Remove.
+
 2011-09-04  Paul Eggert  <[email-masked]>
 
 	* config.nt (HAVE_SNPRINTF): New macro.

=== modified file 'nt/config.nt'
--- nt/config.nt	2011-09-26 03:20:03 +0000
+++ nt/config.nt	2011-10-17 01:22:19 +0000
@@ -271,13 +271,6 @@
 
 /* Preprocessor macros needed for gnulib imports.  */
 
-/* Define to 1 if GCC-style __attribute__ ((__aligned__ (expr))) works. */
-#ifdef __GNUC__
-#define HAVE_ATTRIBUTE_ALIGNED 1
-#else
-#undef HAVE_ATTRIBUTE_ALIGNED
-#endif
-
 /* Define to 1 if strtold conforms to C99. */
 #ifdef __GNUC__
 #define HAVE_C99_STRTOLD 1

=== modified file 'src/ChangeLog'
--- src/ChangeLog	2011-10-15 10:12:00 +0000
+++ src/ChangeLog	2011-10-17 01:22:19 +0000
@@ -1,3 +1,12 @@
+2011-10-17  Paul Eggert  <[email-masked]>
+
+	Use Gnulib stdalign module.
+	* alloc.c (XMALLOC_BASE_ALIGNMENT, GC_LISP_OBJECT_ALIGNMENT)
+	(GC_POINTER_ALIGNMENT, pure_alloc): Simplify by using alignof.
+	(pure_alloc) [! USE_LSB_TAG]: Don't over-align EMACS_INT values.
+	* lisp.h: Include <stdalign.h>.
+	(DECL_ALIGN): Simplify by using alignas.
+
 2011-10-15  Martin Rudalics  <[email-masked]>
 
 	* window.c (coordinates_in_window): Rewrite and delabelize

=== modified file 'src/alloc.c'
--- src/alloc.c	2011-10-12 06:09:40 +0000
+++ src/alloc.c	2011-10-17 01:22:19 +0000
@@ -507,12 +507,7 @@
    hold a size_t value and (2) the header size is a multiple of the
    alignment that Emacs needs for C types and for USE_LSB_TAG.  */
 #define XMALLOC_BASE_ALIGNMENT				\
-  offsetof (						\
-    struct {						\
-      union { long double d; intmax_t i; void *p; } u;	\
-      char c;						\
-    },							\
-    c)
+  alignof (union { long double d; intmax_t i; void *p; })
 #ifdef USE_LSB_TAG
 /* A common multiple of the positive integers A and B.  Ideally this
    would be the least common multiple, but there's no way to do that
@@ -4235,15 +4230,15 @@
 }

-/* Alignment of Lisp_Object and pointer values.  Use offsetof, as it
+/* Alignment of Lisp_Object and pointer values.  Use alignof, as it
    sometimes returns a smaller alignment than GCC's __alignof__ and
    mark_memory might miss objects if __alignof__ were used.  For
    example, on x86 with WIDE_EMACS_INT, __alignof__ (Lisp_Object) is 8
    but GC_LISP_OBJECT_ALIGNMENT should be 4.  */
 #ifndef GC_LISP_OBJECT_ALIGNMENT
-# define GC_LISP_OBJECT_ALIGNMENT offsetof (struct {char a; Lisp_Object b;}, b)
+# define GC_LISP_OBJECT_ALIGNMENT alignof (Lisp_Object)
 #endif
-#define GC_POINTER_ALIGNMENT offsetof (struct {char a; void *b;}, b)
+#define GC_POINTER_ALIGNMENT alignof (void *)
 
 /* Mark Lisp objects referenced from the address range START+OFFSET..END
    or END+OFFSET..START. */
@@ -4662,17 +4657,11 @@
 #ifdef USE_LSB_TAG
   size_t alignment = (1 << GCTYPEBITS);
 #else
-  size_t alignment = sizeof (EMACS_INT);
+  size_t alignment = alignof (EMACS_INT);
 
   /* Give Lisp_Floats an extra alignment.  */
   if (type == Lisp_Float)
-    {
-#if defined __GNUC__ && __GNUC__ >= 2
-      alignment = __alignof (struct Lisp_Float);
-#else
-      alignment = sizeof (struct Lisp_Float);
-#endif
-    }
+    alignment = alignof (struct Lisp_Float);
 #endif
 
  again:

=== modified file 'src/lisp.h'
--- src/lisp.h	2011-10-11 17:35:16 +0000
+++ src/lisp.h	2011-10-17 01:22:19 +0000
@@ -20,6 +20,7 @@
 #ifndef EMACS_LISP_H
 #define EMACS_LISP_H
 
+#include <stdalign.h>
 #include <stdarg.h>
 #include <stddef.h>
 #include <inttypes.h>
@@ -163,15 +164,8 @@
 /* First, try and define DECL_ALIGN(type,var) which declares a static
    variable VAR of type TYPE with the added requirement that it be
    TYPEBITS-aligned. */
-#ifndef NO_DECL_ALIGN
-# ifndef DECL_ALIGN
-#  if HAVE_ATTRIBUTE_ALIGNED
-#   define DECL_ALIGN(type, var) \
-     type __attribute__ ((__aligned__ (1 << GCTYPEBITS))) var
-#  else
-     /* What directives do other compilers use?  */
-#  endif
-# endif
+#ifdef alignas
+# define DECL_ALIGN(type, var) type alignas (1 << GCTYPEBITS) var
 #endif
 
 /* Let's USE_LSB_TAG on systems where we know malloc returns mult-of-8.  */