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/* Copyright (C) 1991-2021 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
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <libc-internal.h>
#include <stdbool.h>
#include <stdint.h>
#include <unistd.h>
/* Defined in brk.c. */
extern void *__curbrk;
extern int __brk (void *addr);
/* 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)
{
/* Controls whether __brk (0) is called to read the brk value from
the kernel. */
bool update_brk = __curbrk == NULL;
#if defined (SHARED) && ! IS_IN (rtld)
if (!__libc_initial)
{
if (increment != 0)
{
/* Do not allow changing the brk from an inner libc because
it cannot be synchronized with the outer libc's brk. */
__set_errno (ENOMEM);
return (void *) -1;
}
/* Querying the kernel's brk value from an inner namespace is
fine. */
update_brk = true;
}
#endif
if (update_brk)
if (__brk (0) < 0) /* Initialize the break. */
return (void *) -1;
if (increment == 0)
return __curbrk;
void *oldbrk = __curbrk;
if (increment > 0
? ((uintptr_t) oldbrk + (uintptr_t) increment < (uintptr_t) oldbrk)
: ((uintptr_t) oldbrk < (uintptr_t) -increment))
{
__set_errno (ENOMEM);
return (void *) -1;
}
if (__brk (oldbrk + increment) < 0)
return (void *) -1;
return oldbrk;
}
libc_hidden_def (__sbrk)
weak_alias (__sbrk, sbrk)
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