Re: sys_socket: sockaddr_storage, new module alignof

[Bruno Haible]

Simon Josefsson wrote:
> +#define _SS_PADSIZE  (_SS_SIZE - (max (sizeof (sa_family_t),         \
> +                                       alignof (__ss_aligntype))     \
> +                                  + sizeof (__ss_aligntype)))

Fine, except that 'alignof' is not a predefined macro. We have a definition
of it in "malloca.h" and in some .c files from glibc. OSF/1 has it in a file
<alignof.h>, but it contains nothing better than our alignof macro.

I propose to create a module like this:

2009-05-08  Bruno Haible  <address@hidden>

        New module 'alignof'.
        * lib/alignof.h: New file.
        * modules/alignof: New file.
        * lib/malloca.h: Include alignof.h.
        (sa_alignof): Remove macro.
        (sa_alignment_*): Use the alignof macro.
        * modules/malloca (Depends-on): Add alignof.

=================================== lib/alignof.h =============================
/* Determine alignment of types.
   Copyright (C) 2003-2004, 2006, 2009 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 2, 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.  */

#ifndef _ALIGNOF_H
#define _ALIGNOF_H

#include <stddef.h>

/* Determine the alignment of a type at compile time.  */
#if defined __GNUC__
# define alignof __alignof__
#elif defined __cplusplus
  template <class type> struct alignof_helper { char __slot1; type __slot2; };
# define alignof(type) offsetof (alignof_helper<type>, __slot2)
#elif defined __hpux
  /* Work around a HP-UX 10.20 cc bug with enums constants defined as offsetof
     values.  */
# define alignof(type) (sizeof (type) <= 4 ? 4 : 8)
#elif defined _AIX
  /* Work around an AIX 3.2.5 xlc bug with enums constants defined as offsetof
     values.  */
# define alignof(type) (sizeof (type) <= 4 ? 4 : 8)
#else
# define alignof(type) offsetof (struct { char __slot1; type __slot2; }, 
__slot2)
#endif

#endif /* _ALIGNOF_H */
================================== modules/alignof ============================
Description:
Determine alignment of types.

Files:
lib/alignof.h

Depends-on:

configure.ac:

Makefile.am:

Include:
"alignof.h"

License:
LGPLv2+

Maintainer:
Bruno Haible
===============================================================================
*** lib/malloca.h.orig  2009-05-08 12:56:57.000000000 +0200
--- lib/malloca.h       2009-05-08 12:56:31.000000000 +0200
***************
*** 1,5 ****
  /* Safe automatic memory allocation.
!    Copyright (C) 2003-2007 Free Software Foundation, Inc.
     Written by Bruno Haible <address@hidden>, 2003.
  
     This program is free software; you can redistribute it and/or modify
--- 1,5 ----
  /* Safe automatic memory allocation.
!    Copyright (C) 2003-2007, 2009 Free Software Foundation, Inc.
     Written by Bruno Haible <address@hidden>, 2003.
  
     This program is free software; you can redistribute it and/or modify
***************
*** 23,28 ****
--- 23,30 ----
  #include <stddef.h>
  #include <stdlib.h>
  
+ #include "alignof.h"
+ 
  
  #ifdef __cplusplus
  extern "C" {
***************
*** 92,125 ****
  
  /* ------------------- Auxiliary, non-public definitions ------------------- 
*/
  
- /* Determine the alignment of a type at compile time.  */
- #if defined __GNUC__
- # define sa_alignof __alignof__
- #elif defined __cplusplus
-   template <class type> struct sa_alignof_helper { char __slot1; type 
__slot2; };
- # define sa_alignof(type) offsetof (sa_alignof_helper<type>, __slot2)
- #elif defined __hpux
-   /* Work around a HP-UX 10.20 cc bug with enums constants defined as offsetof
-      values.  */
- # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
- #elif defined _AIX
-   /* Work around an AIX 3.2.5 xlc bug with enums constants defined as offsetof
-      values.  */
- # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
- #else
- # define sa_alignof(type) offsetof (struct { char __slot1; type __slot2; }, 
__slot2)
- #endif
- 
  enum
  {
  /* The desired alignment of memory allocations is the maximum alignment
     among all elementary types.  */
!   sa_alignment_long = sa_alignof (long),
!   sa_alignment_double = sa_alignof (double),
  #if HAVE_LONG_LONG_INT
!   sa_alignment_longlong = sa_alignof (long long),
  #endif
!   sa_alignment_longdouble = sa_alignof (long double),
    sa_alignment_max = ((sa_alignment_long - 1) | (sa_alignment_double - 1)
  #if HAVE_LONG_LONG_INT
                      | (sa_alignment_longlong - 1)
--- 94,109 ----
  
  /* ------------------- Auxiliary, non-public definitions ------------------- 
*/
  
  enum
  {
  /* The desired alignment of memory allocations is the maximum alignment
     among all elementary types.  */
!   sa_alignment_long = alignof (long),
!   sa_alignment_double = alignof (double),
  #if HAVE_LONG_LONG_INT
!   sa_alignment_longlong = alignof (long long),
  #endif
!   sa_alignment_longdouble = alignof (long double),
    sa_alignment_max = ((sa_alignment_long - 1) | (sa_alignment_double - 1)
  #if HAVE_LONG_LONG_INT
                      | (sa_alignment_longlong - 1)
*** modules/malloca.orig        2009-05-08 12:56:57.000000000 +0200
--- modules/malloca     2009-05-08 12:56:48.000000000 +0200
***************
*** 10,15 ****
--- 10,16 ----
  m4/longlong.m4
  
  Depends-on:
+ alignof
  alloca-opt
  
  configure.ac: