/* Safe automatic memory allocation.

   Copyright (C) 2003-2007, 2009-2020 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 Lesser General Public License as published by

   the Free Software Foundation; either version 2.1, 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 Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License

   along with this program; if not, see <https://www.gnu.org/licenses/>.  */

#ifndef _MALLOCA_H

#define _MALLOCA_H

#include <alloca.h>

#include <stddef.h>

#include <stdlib.h>

#include <stdint.h>

#include "xalloc-oversized.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 a function.  */

# define safe_alloca(N) ((N) < 4032 ? alloca (N) : NULL)

#else

# define safe_alloca(N) ((void) (N), NULL)

#endif

/* malloca(N) is a safe variant of alloca(N).  It allocates N bytes of

   memory allocated on the stack, that must be freed using freea() before

   the function returns.  Upon failure, it returns NULL.  */

#if HAVE_ALLOCA

# define malloca(N) \

  ((N) < 4032 - (2 * sa_alignment_max - 1)                                   \

   ? (void *) (((uintptr_t) (char *) alloca ((N) + 2 * sa_alignment_max - 1) \

                + (2 * sa_alignment_max - 1))                                \

               & ~(uintptr_t)(2 * sa_alignment_max - 1))                     \

   : mmalloca (N))

#else

# define malloca(N) \

  mmalloca (N)

#endif

extern void * mmalloca (size_t n);

/* Free a block of memory allocated through malloca().  */

#if HAVE_ALLOCA

extern void freea (void *p);

#else

# define freea free

#endif

/* nmalloca(N,S) is an overflow-safe variant of malloca (N * S).

   It allocates an array of N objects, each with S bytes of memory,

   on the stack.  S must be positive and N must be nonnegative.

   The array must be freed using freea() before the function returns.  */

#define nmalloca(n, s) (xalloc_oversized (n, s) ? NULL : malloca ((n) * (s)))

#ifdef __cplusplus

}

#endif

/* ------------------- Auxiliary, non-public definitions ------------------- */

/* Determine the alignment of a type at compile time.  */

#if defined __GNUC__ || defined __IBM__ALIGNOF__

# 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),

  sa_alignment_longlong = sa_alignof (long long),

  sa_alignment_longdouble = sa_alignof (long double),

  sa_alignment_max = ((sa_alignment_long - 1) | (sa_alignment_double - 1)

                      | (sa_alignment_longlong - 1)

                      | (sa_alignment_longdouble - 1)

                     ) + 1

};

#endif /* _MALLOCA_H */