diff options
Diffstat (limited to 'gl/m4/stdalign.m4')
| -rw-r--r-- | gl/m4/stdalign.m4 | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/gl/m4/stdalign.m4 b/gl/m4/stdalign.m4 new file mode 100644 index 0000000..dc29717 --- /dev/null +++ b/gl/m4/stdalign.m4 @@ -0,0 +1,138 @@ +# 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]) +]) |