| # Check for stdalign.h that conforms to C11. |
| |
| dnl Copyright 2011-2021 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 working stdalign.h], |
| [gl_cv_header_working_stdalign_h], |
| [AC_COMPILE_IFELSE( |
| [AC_LANG_PROGRAM( |
| [[#include <stdalign.h> |
| #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) \ |
| || (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=yes], |
| [gl_cv_header_working_stdalign_h=no])]) |
| |
| if test $gl_cv_header_working_stdalign_h = yes; then |
| STDALIGN_H='' |
| else |
| STDALIGN_H='stdalign.h' |
| fi |
| |
| AC_SUBST([STDALIGN_H]) |
| AM_CONDITIONAL([GL_GENERATE_STDALIGN_H], [test -n "$STDALIGN_H"]) |
| ]) |
