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58 lines
2.3 KiB
Plaintext
58 lines
2.3 KiB
Plaintext
# Check for stdalign.h that conforms to C11.
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dnl Copyright 2011-2020 Free Software Foundation, Inc.
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dnl This file is free software; the Free Software Foundation
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dnl gives unlimited permission to copy and/or distribute it,
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dnl with or without modifications, as long as this notice is preserved.
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# Prepare for substituting <stdalign.h> if it is not supported.
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AC_DEFUN([gl_STDALIGN_H],
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[
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AC_CACHE_CHECK([for working stdalign.h],
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[gl_cv_header_working_stdalign_h],
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[AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM(
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[[#include <stdalign.h>
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#include <stddef.h>
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/* Test that alignof yields a result consistent with offsetof.
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This catches GCC bug 52023
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<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. */
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#ifdef __cplusplus
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template <class t> struct alignof_helper { char a; t b; };
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# define ao(type) offsetof (alignof_helper<type>, b)
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#else
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# define ao(type) offsetof (struct { char a; type b; }, b)
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#endif
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char test_double[ao (double) % _Alignof (double) == 0 ? 1 : -1];
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char test_long[ao (long int) % _Alignof (long int) == 0 ? 1 : -1];
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char test_alignof[alignof (double) == _Alignof (double) ? 1 : -1];
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/* Test _Alignas only on platforms where gnulib can help. */
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#if \
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((defined __cplusplus && 201103 <= __cplusplus) \
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|| (defined __APPLE__ && defined __MACH__ \
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? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
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: __GNUC__) \
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|| (__ia64 && (61200 <= __HP_cc || 61200 <= __HP_aCC)) \
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|| __ICC || 0x590 <= __SUNPRO_C || 0x0600 <= __xlC__ \
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|| 1300 <= _MSC_VER)
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struct alignas_test { char c; char alignas (8) alignas_8; };
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char test_alignas[offsetof (struct alignas_test, alignas_8) == 8
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? 1 : -1];
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#endif
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]])],
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[gl_cv_header_working_stdalign_h=yes],
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[gl_cv_header_working_stdalign_h=no])])
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if test $gl_cv_header_working_stdalign_h = yes; then
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STDALIGN_H=''
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else
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STDALIGN_H='stdalign.h'
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fi
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AC_SUBST([STDALIGN_H])
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AM_CONDITIONAL([GL_GENERATE_STDALIGN_H], [test -n "$STDALIGN_H"])
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])
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