#include <unistd.h>

       int brk(void *addr);

       void *sbrk(intptr_t increment);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       brk(), sbrk():
           Since glibc 2.12:
               _BSD_SOURCE || _SVID_SOURCE ||
                   (_XOPEN_SOURCE >= 500 ||
                       _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) &&
                   !(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600)
           Before glibc 2.12:
               _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||

       brk() and sbrk() change  the  location  of  the  program  break,  which
       defines  the end of the process's data segment (i.e., the program break
       is the first location after the end of the uninitialized data segment).
       Increasing the program break has the effect of allocating memory to the
       process; decreasing the break deallocates memory.

       brk() sets the end of the data segment to the value specified by  addr,
       when  that  value  is reasonable, the system has enough memory, and the
       process does not exceed its maximum data size (see setrlimit(2)).

       sbrk() increments the program's data space by increment bytes.  Calling
       sbrk()  with an increment of 0 can be used to find the current location
       of the program break.

       On success, brk() returns zero.  On error, -1 is returned, and errno is
       set to ENOMEM.

       On  success,  sbrk() returns the previous program break.  (If the break
       was increased, then this value is a pointer to the start of  the  newly
       allocated memory).  On error, (void *) -1 is returned, and errno is set
       to ENOMEM.

       4.3BSD; SUSv1, marked LEGACY in SUSv2, removed in POSIX.1-2001.

       Avoid using brk() and sbrk(): the malloc(3) memory  allocation  package
       is the portable and comfortable way of allocating memory.

       Various  systems  use various types for the argument of sbrk().  Common
       are int, ssize_t, ptrdiff_t, intptr_t.

   C library/kernel differences
       The return value described above for brk() is the behavior provided  by

       execve(2), getrlimit(2), end(3), malloc(3)

       This  page  is  part of release 4.04 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at

Linux                             2015-07-23                            BRK(2)
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