svcadm(8)을 검색하려면 섹션에서 8 을 선택하고, 맨 페이지 이름에 svcadm을 입력하고 검색을 누른다.
sbrk(2)
brk(2) System Calls brk(2)
NAME
brk, sbrk - change the amount of space allocated for the calling
process's data segment
SYNOPSIS
#include <unistd.h>
int brk(void *endds);
void *sbrk(intptr_t incr);
DESCRIPTION
The brk() and sbrk() functions are used to change the amount of space
allocated for the calling process's data segment (see exec(2)). The
change is made by resetting the process's break value and allocating
the appropriate amount of space. The break value is the address of the
first location beyond the end of the data segment. The amount of allo‐
cated space increases as the break value increases. Newly allocated
space is set to zero. If, however, the same memory space is reallocated
to the same process its contents are undefined.
When a program begins execution using execve() the break is set at the
highest location defined by the program and data storage areas.
The getrlimit(2) function may be used to determine the maximum permis‐
sible size of the data segment; it is not possible to set the break be‐
yond the rlim_max value returned from a call to getrlimit(), that is to
say, "end + rlim.rlim_max." See end(3C).
The brk() function sets the break value to endds and changes the allo‐
cated space accordingly.
The sbrk() function adds incr function bytes to the break value and
changes the allocated space accordingly. The incr function can be nega‐
tive, in which case the amount of allocated space is decreased.
RETURN VALUES
Upon successful completion, brk() returns 0. Otherwise, it returns −1
and sets errno to indicate the error.
Upon successful completion, sbrk() returns the prior break value. Oth‐
erwise, it returns (void *)−1 and sets errno to indicate the error.
ERRORS
The brk() and sbrk() functions will fail and no additional memory will
be allocated if:
ENOMEM The data segment size limit as set by setrlimit(2) would be
exceeded; the maximum possible size of a data segment would
be exceeded; insufficient space exists in the swap area to
support the expansion; or the new break value would extend
into an area of the address space defined by some previously
established mapping (see mmap(2)).
EAGAIN Total amount of system memory available for private pages is
temporarily insufficient. This may occur even though the
space requested was less than the maximum data segment size
(see ulimit(2)).
USAGE
The behavior of brk() and sbrk() is unspecified if an application also
uses any other memory functions (such as malloc(3C), mmap(2),
free(3C)). The brk() and sbrk() functions have been used in specialized
cases where no other memory allocation function provided the same capa‐
bility. The use of mmap(2) is now preferred because it can be used
portably with all other memory allocation functions and with any func‐
tion that uses other allocation functions.
It is unspecified whether the pointer returned by sbrk() is aligned
suitably for any purpose.
Memory allocated by this function may be on pages with the PROT_EXEC
access protections disabled to block execution of machine instructions,
depending on the current settings for NXHEAP in sxadm(8) and any -z
sx=nxheap options that were passed to ld(1) when linking the applica‐
tion. These settings may be overridden for specific pages by calling
mprotect(2).
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ Interface StabilityCommitted _ MT-LevelMT-Safe
SEE ALSO
exec(2), getrlimit(2), mmap(2), mprotect(2), shmop(2), ulimit(2),
end(3C), free(3C), malloc(3C)
NOTES
The value of incr may be adjusted by the system before setting the new
break value. Upon successful completion, the implementation guarantees
a minimum of incr bytes will be added to the data segment if incr is a
positive value. If incr is a negative value, a maximum of incr bytes
will be removed from the data segment. This adjustment may not be nec‐
essary for all machine architectures.
The value of the arguments to both brk() and sbrk() are rounded up for
alignment with eight-byte boundaries.
BUGS
Setting the break may fail due to a temporary lack of swap space. It is
not possible to distinguish this from a failure caused by exceeding the
maximum size of the data segment without consulting getrlimit().
HISTORY
The brk() and sbrk() functions have been included in all Sun and Oracle
releases of Solaris.
Oracle Solaris 11.4 30 Jan 2023 brk(2)