1# Check for stdalign.h that conforms to C11. 2 3dnl Copyright 2011-2022 Free Software Foundation, Inc. 4dnl This file is free software; the Free Software Foundation 5dnl gives unlimited permission to copy and/or distribute it, 6dnl with or without modifications, as long as this notice is preserved. 7 8# Prepare for substituting <stdalign.h> if it is not supported. 9 10AC_DEFUN([gl_STDALIGN_H], 11[ 12 AC_CACHE_CHECK([for working stdalign.h], 13 [gl_cv_header_working_stdalign_h], 14 [AC_COMPILE_IFELSE( 15 [AC_LANG_PROGRAM( 16 [[#include <stdint.h> 17 #include <stdalign.h> 18 #include <stddef.h> 19 20 /* Test that alignof yields a result consistent with offsetof. 21 This catches GCC bug 52023 22 <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. */ 23 #ifdef __cplusplus 24 template <class t> struct alignof_helper { char a; t b; }; 25 # define ao(type) offsetof (alignof_helper<type>, b) 26 #else 27 # define ao(type) offsetof (struct { char a; type b; }, b) 28 #endif 29 char test_double[ao (double) % _Alignof (double) == 0 ? 1 : -1]; 30 char test_long[ao (long int) % _Alignof (long int) == 0 ? 1 : -1]; 31 char test_alignof[alignof (double) == _Alignof (double) ? 1 : -1]; 32 33 /* Test _Alignas only on platforms where gnulib can help. */ 34 #if \ 35 ((defined __cplusplus && 201103 <= __cplusplus) \ 36 || (__TINYC__ && defined __attribute__) \ 37 || (defined __APPLE__ && defined __MACH__ \ 38 ? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \ 39 : __GNUC__) \ 40 || (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \ 41 || __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__ \ 42 || 1300 <= _MSC_VER) 43 struct alignas_test { char c; char alignas (8) alignas_8; }; 44 char test_alignas[offsetof (struct alignas_test, alignas_8) == 8 45 ? 1 : -1]; 46 #endif 47 ]])], 48 [gl_cv_header_working_stdalign_h=yes], 49 [gl_cv_header_working_stdalign_h=no])]) 50 51 if test $gl_cv_header_working_stdalign_h = yes; then 52 GL_GENERATE_STDALIGN_H=false 53 else 54 GL_GENERATE_STDALIGN_H=true 55 fi 56]) 57