| 1 | # Check for stdalign.h that conforms to C11.
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| 2 |
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| 3 | dnl Copyright 2011-2021 Free Software Foundation, Inc.
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| 4 | dnl This file is free software; the Free Software Foundation
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| 5 | dnl gives unlimited permission to copy and/or distribute it,
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| 6 | dnl with or without modifications, as long as this notice is preserved.
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| 7 |
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| 8 | # Prepare for substituting <stdalign.h> if it is not supported.
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| 9 |
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| 10 | AC_DEFUN([gl_STDALIGN_H],
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| 11 | [
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| 12 | AC_CACHE_CHECK([for working stdalign.h],
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| 13 | [gl_cv_header_working_stdalign_h],
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| 14 | [AC_COMPILE_IFELSE(
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| 15 | [AC_LANG_PROGRAM(
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| 16 | [[#include <stdint.h>
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| 17 | #include <stdalign.h>
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| 18 | #include <stddef.h>
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| 19 |
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| 20 | /* Test that alignof yields a result consistent with offsetof.
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| 21 | This catches GCC bug 52023
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| 22 | <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. */
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| 23 | #ifdef __cplusplus
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| 24 | template <class t> struct alignof_helper { char a; t b; };
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| 25 | # define ao(type) offsetof (alignof_helper<type>, b)
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| 26 | #else
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| 27 | # define ao(type) offsetof (struct { char a; type b; }, b)
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| 28 | #endif
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| 29 | char test_double[ao (double) % _Alignof (double) == 0 ? 1 : -1];
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| 30 | char test_long[ao (long int) % _Alignof (long int) == 0 ? 1 : -1];
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| 31 | char test_alignof[alignof (double) == _Alignof (double) ? 1 : -1];
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| 32 |
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| 33 | /* Test _Alignas only on platforms where gnulib can help. */
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| 34 | #if \
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| 35 | ((defined __cplusplus && 201103 <= __cplusplus) \
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| 36 | || (__TINYC__ && defined __attribute__) \
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| 37 | || (defined __APPLE__ && defined __MACH__ \
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| 38 | ? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
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| 39 | : __GNUC__) \
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| 40 | || (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \
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| 41 | || __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__ \
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| 42 | || 1300 <= _MSC_VER)
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| 43 | struct alignas_test { char c; char alignas (8) alignas_8; };
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| 44 | char test_alignas[offsetof (struct alignas_test, alignas_8) == 8
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| 45 | ? 1 : -1];
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| 46 | #endif
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| 47 | ]])],
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| 48 | [gl_cv_header_working_stdalign_h=yes],
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| 49 | [gl_cv_header_working_stdalign_h=no])])
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| 50 |
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| 51 | if test $gl_cv_header_working_stdalign_h = yes; then
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| 52 | STDALIGN_H=''
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| 53 | else
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| 54 | STDALIGN_H='stdalign.h'
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| 55 | fi
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| 56 |
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| 57 | AC_SUBST([STDALIGN_H])
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| 58 | AM_CONDITIONAL([GL_GENERATE_STDALIGN_H], [test -n "$STDALIGN_H"])
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| 59 | ])
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