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emacs/m4/flexmember.m4
Paul Eggert fa90c5e86e Merge from gnulib
This gets Emacs working again with HP-UX Itanium cc.
It incorporates:
2017-03-19 stdalign: tweak version# and test for HP-UX IA64
2017-03-18 stdalign: restore previous behavior for HP-UX IA64
2017-03-17 stat-time, timespec: Support header files in C++ mode
2017-03-17 stdalign: Make it work with HP-UX cc
2017-03-17 flexmember: try to detect HP-UX 11.31 cc bug
2017-03-16 stdint: Fix test compilation failure with HP-UX 11 cc.
2017-03-14 gnulib-tool: don't produce tests with only snippets
2017-03-14 limits-h: Make it work with HP-UX cc.
* etc/PROBLEMS: Remove now-obsolete entry for HP-UX 11.31.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* lib/limits.in.h, lib/stat-time.h, lib/stdalign.in.h:
* lib/stdint.in.h, lib/timespec.h, m4/flexmember.m4, m4/stdalign.m4:
Copy from gnulib.
2017-03-19 13:09:31 -07:00

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