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From: kelvin@cascabel.UUCP (Kelvin Nilsen)
Newsgroups: comp.unix.xenix
Subject: Re: sbrk in Xenix
Message-ID: <203@cascabel.UUCP>
Date: Sun, 3-May-87 10:48:04 EDT
Article-I.D.: cascabel.203
Posted: Sun May  3 10:48:04 1987
Date-Received: Sun, 3-May-87 21:57:09 EDT
References: <5816@shemp.UCLA.EDU>
Distribution: world
Organization: Mom 'n Pop Software Shop, Tucson, AZ
Lines: 30

> If I understand the documentation correctly sbrk allocates within
> _DATA. Is this correct? How can I increase the amount that I am able
> to sbrk? is there anyway to change which segment it works off of?
> does -F affect the space that this has available?
> 
> thanks
> Dan

we ran into some problems with this in porting Icon to Xenix.  When
writing Large or Huge memory model program, sbrk is able to return
more than 64K of memory to the user program.  however, the allocated
data is not necessarily contiguous.  this was a great inconvenience to
us, so we complained to SCO about the feature.  their response was that
it was not their fault, but Intel's.  They suggested we wait for 
Xenix-386.

unlike real Unix on a VAX, for example, "sbrk(0) does not necessarily
return the starting address of the next sbrk call."  makes it kind
of hard to allocate using brk().

i just noticed a man page for brkctl which seems to give a little more
explicit control over where memory is allocated from.

good luck,
-- 

kelvin nilsen

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