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glibc/misc/sbrk.c
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/* Copyright (C) 1991-2016 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)) | |
{ | |
__set_errno (ENOMEM); | |
return (void *) -1; | |
} | |
if (__brk (oldbrk + increment) < 0) | |
return (void *) -1; | |
return oldbrk; | |
} | |
libc_hidden_def (__sbrk) | |
weak_alias (__sbrk, sbrk) |