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220a9ecba1
This incorporates: 2018-01-01 maint: Run 'make update-copyright' 2017-12-29 Add cross-compilation results for GNU/Hurd. 2017-12-12 explicit_bzero: port to macOS + Clang 9.0.0
47 lines
1.8 KiB
Plaintext
47 lines
1.8 KiB
Plaintext
# serial 5
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# Check for flexible array member support.
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# Copyright (C) 2006, 2009-2018 Free Software Foundation, Inc.
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# This file is free software; the Free Software Foundation
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# gives unlimited permission to copy and/or distribute it,
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# with or without modifications, as long as this notice is preserved.
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# Written by Paul Eggert.
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AC_DEFUN([AC_C_FLEXIBLE_ARRAY_MEMBER],
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[
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AC_CACHE_CHECK([for flexible array member],
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ac_cv_c_flexmember,
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[AC_COMPILE_IFELSE(
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[AC_LANG_PROGRAM(
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[[#include <stdlib.h>
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#include <stdio.h>
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#include <stddef.h>
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struct m { struct m *next, **list; char name[]; };
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struct s { struct s *p; struct m *m; int n; double d[]; };]],
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[[int m = getchar ();
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size_t nbytes = offsetof (struct s, d) + m * sizeof (double);
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nbytes += sizeof (struct s) - 1;
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nbytes -= nbytes % sizeof (struct s);
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struct s *p = malloc (nbytes);
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p->p = p;
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p->m = NULL;
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p->d[0] = 0.0;
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return p->d != (double *) NULL;]])],
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[ac_cv_c_flexmember=yes],
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[ac_cv_c_flexmember=no])])
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if test $ac_cv_c_flexmember = yes; then
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AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [],
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[Define to nothing if C supports flexible array members, and to
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1 if it does not. That way, with a declaration like 'struct s
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{ int n; double d@<:@FLEXIBLE_ARRAY_MEMBER@:>@; };', the struct hack
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can be used with pre-C99 compilers.
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When computing the size of such an object, don't use 'sizeof (struct s)'
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as it overestimates the size. Use 'offsetof (struct s, d)' instead.
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Don't use 'offsetof (struct s, d@<:@0@:>@)', as this doesn't work with
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MSVC and with C++ compilers.])
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else
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AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [1])
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fi
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])
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