where to place shared memory segments?

[Hannes Lubich]

Hi,
following figure 2.2 and his remark regarding shmbrk below figure 3.30
in W. Richard Stevens'book "Unix Network Programming" it seems that
shared memory segments are "normally" placed between the heap and the
stack segment of a process address space. I was asked recently why such
segments couldn't be put on the heap just as other dynamically allocated
data structures.

Besides the argument that heap administration is something totally unrelated 
to allocation of shared memory segments, ist there any serious problems with
placing shared memory on the heap? Are there any advantages, even?
Thanks a lot in advance
	--HaL
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