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- # Check for stdalign.h that conforms to C11.
- dnl Copyright 2011-2014 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
- <http://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) \
- || __GNUC__ || __IBMC__ || __IBMCPP__ || __ICC \
- || 0x5110 <= __SUNPRO_C || 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"])
- ])
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