139 lines
5.4 KiB
Plaintext
139 lines
5.4 KiB
Plaintext
# Check for alignas and alignof that conform to C23.
|
|
|
|
dnl Copyright 2011-2023 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_CACHE_CHECK([for alignas and alignof],
|
|
[gl_cv_header_working_stdalign_h],
|
|
[gl_save_CFLAGS=$CFLAGS
|
|
for gl_working in "yes, keywords" "yes, <stdalign.h> macros"; do
|
|
AS_CASE([$gl_working],
|
|
[*stdalign.h*], [CFLAGS="$gl_save_CFLAGS -DINCLUDE_STDALIGN_H"])
|
|
AC_COMPILE_IFELSE(
|
|
[AC_LANG_PROGRAM(
|
|
[[#include <stdint.h>
|
|
#ifdef INCLUDE_STDALIGN_H
|
|
#include <stdalign.h>
|
|
#endif
|
|
#include <stddef.h>
|
|
|
|
/* Test that alignof yields a result consistent with offsetof.
|
|
This catches GCC bug 52023
|
|
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. */
|
|
#ifdef __cplusplus
|
|
template <class t> struct alignof_helper { char a; t b; };
|
|
# define ao(type) offsetof (alignof_helper<type>, b)
|
|
#else
|
|
# define ao(type) offsetof (struct { char a; type b; }, b)
|
|
#endif
|
|
char test_double[ao (double) % _Alignof (double) == 0 ? 1 : -1];
|
|
char test_long[ao (long int) % _Alignof (long int) == 0 ? 1 : -1];
|
|
char test_alignof[alignof (double) == _Alignof (double) ? 1 : -1];
|
|
|
|
/* Test alignas only on platforms where gnulib can help. */
|
|
#if \
|
|
((defined __cplusplus && 201103 <= __cplusplus) \
|
|
|| (__TINYC__ && defined __attribute__) \
|
|
|| (defined __APPLE__ && defined __MACH__ \
|
|
? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
|
|
: __GNUC__) \
|
|
|| (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \
|
|
|| __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__ \
|
|
|| 1300 <= _MSC_VER)
|
|
struct alignas_test { char c; char alignas (8) alignas_8; };
|
|
char test_alignas[offsetof (struct alignas_test, alignas_8) == 8
|
|
? 1 : -1];
|
|
#endif
|
|
]])],
|
|
[gl_cv_header_working_stdalign_h=$gl_working],
|
|
[gl_cv_header_working_stdalign_h=no])
|
|
|
|
CFLAGS=$gl_save_CFLAGS
|
|
test "$gl_cv_header_working_stdalign_h" != no && break
|
|
done])
|
|
|
|
GL_GENERATE_STDALIGN_H=false
|
|
AS_CASE([$gl_cv_header_working_stdalign_h],
|
|
[no],
|
|
[GL_GENERATE_STDALIGN_H=true],
|
|
[yes*keyword*],
|
|
[AC_DEFINE([HAVE_C_ALIGNASOF], [1],
|
|
[Define to 1 if the alignas and alignof keywords work.])])
|
|
|
|
AC_CHECK_HEADERS_ONCE([stdalign.h])
|
|
|
|
dnl The "zz" puts this toward config.h's end, to avoid potential
|
|
dnl collisions with other definitions.
|
|
AH_VERBATIM([zzalignas],
|
|
[#if !defined HAVE_C_ALIGNASOF && __cplusplus < 201103 && !defined alignof
|
|
# if HAVE_STDALIGN_H
|
|
# include <stdalign.h>
|
|
# else
|
|
/* Substitute. Keep consistent with gnulib/lib/stdalign.in.h. */
|
|
# ifndef _GL_STDALIGN_H
|
|
# define _GL_STDALIGN_H
|
|
# undef _Alignas
|
|
# undef _Alignof
|
|
# if (!defined __STDC_VERSION__ || __STDC_VERSION__ < 201112 \
|
|
|| (defined __GNUC__ && __GNUC__ < 4 + (__GNUC_MINOR__ < 9) \
|
|
&& !defined __clang__) \
|
|
|| (defined __clang__ && __clang_major__ < 8))
|
|
# ifdef __cplusplus
|
|
# if (201103 <= __cplusplus || defined _MSC_VER)
|
|
# define _Alignof(type) alignof (type)
|
|
# else
|
|
template <class __t> struct __alignof_helper { char __a; __t __b; };
|
|
# define _Alignof(type) offsetof (__alignof_helper<type>, __b)
|
|
# define _GL_STDALIGN_NEEDS_STDDEF 1
|
|
# endif
|
|
# else
|
|
# if (defined __GNUC__ && 4 <= __GNUC__) || defined __clang__
|
|
# define _Alignof(type) __builtin_offsetof (struct { char __a; type __b; }, __b)
|
|
# else
|
|
# define _Alignof(type) offsetof (struct { char __a; type __b; }, __b)
|
|
# define _GL_STDALIGN_NEEDS_STDDEF 1
|
|
# endif
|
|
# endif
|
|
# endif
|
|
# if ! (defined __cplusplus && (201103 <= __cplusplus || defined _MSC_VER))
|
|
# define alignof _Alignof
|
|
# endif
|
|
# define __alignof_is_defined 1
|
|
# if !defined __STDC_VERSION__ || __STDC_VERSION__ < 201112
|
|
# if defined __cplusplus && (201103 <= __cplusplus || defined _MSC_VER)
|
|
# define _Alignas(a) alignas (a)
|
|
# elif (!defined __attribute__ \
|
|
&& ((defined __APPLE__ && defined __MACH__ \
|
|
? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
|
|
: __GNUC__ && !defined __ibmxl__) \
|
|
|| (4 <= __clang_major__) \
|
|
|| (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \
|
|
|| __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__))
|
|
# define _Alignas(a) __attribute__ ((__aligned__ (a)))
|
|
# elif 1300 <= _MSC_VER
|
|
# define _Alignas(a) __declspec (align (a))
|
|
# endif
|
|
# endif
|
|
# if ((defined _Alignas \
|
|
&& !(defined __cplusplus && (201103 <= __cplusplus || defined _MSC_VER))) \
|
|
|| (defined __STDC_VERSION__ && 201112 <= __STDC_VERSION__))
|
|
# define alignas _Alignas
|
|
# endif
|
|
# if (defined alignas \
|
|
|| (defined __cplusplus && (201103 <= __cplusplus || defined _MSC_VER)))
|
|
# define __alignas_is_defined 1
|
|
# endif
|
|
# if _GL_STDALIGN_NEEDS_STDDEF
|
|
# include <stddef.h>
|
|
# endif
|
|
# endif /* _GL_STDALIGN_H */
|
|
# endif
|
|
#endif])
|
|
])
|