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d9741b61c8
This removes a workaround where Emacs did not use flexible array members when compiled with IBM XL C. Instead, avoid the problem by making the aliasing issues more obvious to this compiler. * admin/merge-gnulib: Don’t remove m4/flexmember.m4. * m4/flexmember.m4: Copy from gnulib. * configure.ac (AC_C_FLEXIBLE_ARRAY_MEMBER): Remove workaround. * src/alloc.c (allocate_string_data): Rephrase to avoid aliasing problem that would otherwise mess up code generated for flexible array members by IBM XL C for AIX, V12.1. * src/conf_post.h (FLEXIBLE_ARRAY_MEMBER): Remove; now done by gnulib code.
43 lines
1.7 KiB
Text
43 lines
1.7 KiB
Text
# serial 4
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# Check for flexible array member support.
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# Copyright (C) 2006, 2009-2016 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 s { 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->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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