[thirdparty/glibc.git] / misc / sbrk.c

/* Copyright (C) 1991-2015 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library 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 of the License, or (at your option) any later version.

   The GNU C Library 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 the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <errno.h>
#include <stdint.h>
#include <unistd.h>

/* Defined in brk.c.  */
extern void *__curbrk;
extern int __brk (void *addr);

/* Defined in init-first.c.  */
extern int __libc_multiple_libcs attribute_hidden;

/* Extend the process's data space by INCREMENT.
   If INCREMENT is negative, shrink data space by - INCREMENT.
   Return start of new space allocated, or -1 for errors.  */
void *
__sbrk (intptr_t increment)
{
  void *oldbrk;

  /* If this is not part of the dynamic library or the library is used
     via dynamic loading in a statically linked program update
     __curbrk from the kernel's brk value.  That way two separate
     instances of __brk and __sbrk can share the heap, returning
     interleaved pieces of it.  */
  if (__curbrk == NULL || __libc_multiple_libcs)
    if (__brk (0) < 0)		/* Initialize the break.  */
      return (void *) -1;

  if (increment == 0)
    return __curbrk;

  oldbrk = __curbrk;
  if ((increment > 0
       ? ((uintptr_t) oldbrk + (uintptr_t) increment < (uintptr_t) oldbrk)
       : ((uintptr_t) oldbrk < (uintptr_t) -increment))
      || __brk (oldbrk + increment) < 0)
    return (void *) -1;

  return oldbrk;
}
libc_hidden_def (__sbrk)
weak_alias (__sbrk, sbrk)
Commit	Line	Data
	1	/* Copyright (C) 1991-2015 Free Software Foundation, Inc.
	2	This file is part of the GNU C Library.
	3
	4	The GNU C Library is free software; you can redistribute it and/or
	5	modify it under the terms of the GNU Lesser General Public
	6	License as published by the Free Software Foundation; either
	7	version 2.1 of the License, or (at your option) any later version.
	8
	9	The GNU C Library is distributed in the hope that it will be useful,
	10	but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	12	Lesser General Public License for more details.
	13
	14	You should have received a copy of the GNU Lesser General Public
	15	License along with the GNU C Library; if not, see
	16	<http://www.gnu.org/licenses/>. */
	17
	18	#include <errno.h>
	19	#include <stdint.h>
	20	#include <unistd.h>
	21
	22	/* Defined in brk.c. */
	23	extern void *__curbrk;
	24	extern int __brk (void *addr);
	25
	26	/* Defined in init-first.c. */
	27	extern int __libc_multiple_libcs attribute_hidden;
	28
	29	/* Extend the process's data space by INCREMENT.
	30	If INCREMENT is negative, shrink data space by - INCREMENT.
	31	Return start of new space allocated, or -1 for errors. */
	32	void *
	33	__sbrk (intptr_t increment)
	34	{
	35	void *oldbrk;
	36
	37	/* If this is not part of the dynamic library or the library is used
	38	via dynamic loading in a statically linked program update
	39	__curbrk from the kernel's brk value. That way two separate
	40	instances of __brk and __sbrk can share the heap, returning
	41	interleaved pieces of it. */
	42	if (__curbrk == NULL \|\| __libc_multiple_libcs)
	43	if (__brk (0) < 0) /* Initialize the break. */
	44	return (void *) -1;
	45
	46	if (increment == 0)
	47	return __curbrk;
	48
	49	oldbrk = __curbrk;
	50	if ((increment > 0
	51	? ((uintptr_t) oldbrk + (uintptr_t) increment < (uintptr_t) oldbrk)
	52	: ((uintptr_t) oldbrk < (uintptr_t) -increment))
	53	\|\| __brk (oldbrk + increment) < 0)
	54	return (void *) -1;
	55
	56	return oldbrk;
	57	}
	58	libc_hidden_def (__sbrk)
	59	weak_alias (__sbrk, sbrk)