From:	cgjks1 AT lut DOT ac DOT uk (James Soutter)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: sbrk ?
Date:	28 Oct 1996 18:04:17 GMT
Organization:	Loughborough University, UK.
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Distribution:	world
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References:	<54qkhh$j8h AT salomon DOT mchp DOT siemens DOT de> <54s77r$phg AT sun-cc204 DOT lboro DOT ac DOT uk> <54se3i$ifp AT salomon DOT mchp DOT siemens DOT de>
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To:	djgpp AT delorie DOT com
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Ulrich Lauther (lauther AT cayley DOT zfe DOT siemens DOT de) wrote:
: James Soutter (cgjks1 AT lut DOT ac DOT uk) wrote:
: : 
: : Excuse my ignorance by why use sbrk().  I thought changing sbrk() was a
: : bad idea because it broke the library functions that called malloc().
: : 
: you didn't read my question. I need it under Visual C++ (which I am
: *forced* to use).  I cannot use malloc (at least not conveniently) as
: I need memory aligned to 4096 byte boundaries.

My question was really about the use of sbrk() rather than your
particular situation.

 
: : In DJGPP, why not just use "__dpmi_allocate_memory" to allocate new
: : memory for the memory manager (I havn't tried this).  Similarly under
: : UNIX, why not just use mmap on /dev/zero to allocate memory (it works
: : for me).
: 
: all UNIXes? (Need SunOS, Solaris, Linux, HP-UX).

I have tried SunOS and Linux and mmap'ing /dev/zero works.  Solaris is
probably also ok because it is designed to be some what compatibility
with SunOS but I don't have access to a Solaris box.

HP-UX does not have a "/dev/zero".  Weird operating system.

Does sbrk() work on all UNIX operating systems?  I have always been
scared off by the SunOS Manual on sbrk() [quoted below].  The HP-UX
manual says something similar but the language is not as strong.

> WARNINGS
>      Programs combining the brk() and  sbrk()  system  calls  and
>      malloc()  will not work.  Many library routines use malloc()
>      internally, so use brk() and sbrk() only when you know  that
>      malloc() definitely will not be used by any library routine.


-- James

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