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diff --git a/lib/allocsa.h b/lib/allocsa.h
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+/* Safe automatic memory allocation.
+   Copyright (C) 2003-2007 Free Software Foundation, Inc.
+   Written by Bruno Haible <bruno@clisp.org>, 2003.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+#ifndef _ALLOCSA_H
+#define _ALLOCSA_H
+
+#include <alloca.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/* safe_alloca(N) is equivalent to alloca(N) when it is safe to call
+   alloca(N); otherwise it returns NULL.  It either returns N bytes of
+   memory allocated on the stack, that lasts until the function returns,
+   or NULL.
+   Use of safe_alloca should be avoided:
+     - inside arguments of function calls - undefined behaviour,
+     - in inline functions - the allocation may actually last until the
+       calling function returns.
+*/
+#if HAVE_ALLOCA
+/* The OS usually guarantees only one guard page at the bottom of the stack,
+   and a page size can be as small as 4096 bytes.  So we cannot safely
+   allocate anything larger than 4096 bytes.  Also care for the possibility
+   of a few compiler-allocated temporary stack slots.
+   This must be a macro, not an inline function.  */
+# define safe_alloca(N) ((N) < 4032 ? alloca (N) : NULL)
+#else
+# define safe_alloca(N) ((void) (N), NULL)
+#endif
+
+/* allocsa(N) is a safe variant of alloca(N).  It allocates N bytes of
+   memory allocated on the stack, that must be freed using freesa() before
+   the function returns.  Upon failure, it returns NULL.  */
+#if HAVE_ALLOCA
+# define allocsa(N) \
+  ((N) < 4032 - sa_increment					    \
+   ? (void *) ((char *) alloca ((N) + sa_increment) + sa_increment) \
+   : mallocsa (N))
+#else
+# define allocsa(N) \
+  mallocsa (N)
+#endif
+extern void * mallocsa (size_t n);
+
+/* Free a block of memory allocated through allocsa().  */
+#if HAVE_ALLOCA
+extern void freesa (void *p);
+#else
+# define freesa free
+#endif
+
+/* Maybe we should also define a variant
+    nallocsa (size_t n, size_t s) - behaves like allocsa (n * s)
+   If this would be useful in your application. please speak up.  */
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+/* ------------------- Auxiliary, non-public definitions ------------------- */
+
+/* Determine the alignment of a type at compile time.  */
+#if defined __GNUC__
+# define sa_alignof __alignof__
+#elif defined __cplusplus
+  template <class type> struct sa_alignof_helper { char __slot1; type __slot2; };
+# define sa_alignof(type) offsetof (sa_alignof_helper<type>, __slot2)
+#elif defined __hpux
+  /* Work around a HP-UX 10.20 cc bug with enums constants defined as offsetof
+     values.  */
+# define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
+#elif defined _AIX
+  /* Work around an AIX 3.2.5 xlc bug with enums constants defined as offsetof
+     values.  */
+# define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
+#else
+# define sa_alignof(type) offsetof (struct { char __slot1; type __slot2; }, __slot2)
+#endif
+
+enum
+{
+/* The desired alignment of memory allocations is the maximum alignment
+   among all elementary types.  */
+  sa_alignment_long = sa_alignof (long),
+  sa_alignment_double = sa_alignof (double),
+#if HAVE_LONG_LONG_INT
+  sa_alignment_longlong = sa_alignof (long long),
+#endif
+  sa_alignment_longdouble = sa_alignof (long double),
+  sa_alignment_max = ((sa_alignment_long - 1) | (sa_alignment_double - 1)
+#if HAVE_LONG_LONG_INT
+		      | (sa_alignment_longlong - 1)
+#endif
+		      | (sa_alignment_longdouble - 1)
+		     ) + 1,
+/* The increment that guarantees room for a magic word must be >= sizeof (int)
+   and a multiple of sa_alignment_max.  */
+  sa_increment = ((sizeof (int) + sa_alignment_max - 1) / sa_alignment_max) * sa_alignment_max
+};
+
+#endif /* _ALLOCSA_H */