Each Unix process owns a specific memory region called the
heap, which is used to satisfy the process's
dynamic memory requests. The
brk fields of the memory descriptor delimit
the starting and ending addresses, respectively, of that region.
The following APIs can be used by the process to request and release dynamic memory:
size bytes of
dynamic memory; if the allocation succeeds, it returns the linear
address of the first memory location.
Requests an array consisting of
n elements of size
size; if the allocation succeeds, it
initializes the array components to 0 and returns the linear
address of the first element.
Changes the size of a memory area previously allocated by
malloc( ) or
Releases the memory region allocated by
malloc( ) or
calloc( ) that has an initial address of
Modifies the size of the heap directly; the
addr parameter specifies the new value
the return value is the new ending address of the memory region
(the process must check whether it coincides with the requested
Is similar to
, except that the
incr parameter specifies the increment
or decrement of the heap size in bytes.
brk( ) function differs
from the other functions listed because it is the only one implemented
as a system call. All the other functions are implemented in the C
library by using
brk( ) and
When a process ...