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Re: Controlling allocation in 64-bit space

Le Fri, Mar 24, 2006 at 10:44:43PM +0100, Goswin von Brederlow écrivait/wrote:
> Basile STARYNKEVITCH <basile@starynkevitch.net> writes:
> >
> > I suggest more precisely to 
> >    mmap((void*)0, (size_t)size, PROT_READ|PROT_WRITE, 
> >         MAP_PRIVATE|MAP_ANONYMOUS, (int)-1 /*no fd*/, (off_t)0)
> >
> > with MAP_ANONYMOUS you don't need to open /dev/zero (but internally it is
> > the same)
> >
> > Regards
> Is that protable or just a linux speciality?

It exists in recent Solaris, Linux, BSD. And should be conformant to SUSv3 but not SUSv2. the UNIX (from SCO) has it

I tend to believe that you can test #ifdef MAP_ANONYMOUS; if it is not
defined, you'll need to open /dev/zero.

I don't know if the availability of /dev/zero is more common today

MAP_ANONYMOUS is not a linuxism anymore (IIRC, SunOS got it
before). But I can't be sure that every Unix have it... (IIRC, SunOS4
did not have it, but SunOS5 have it). And MAP_ANONYMOUS is quite common.

Google for mmap & MAP_ANONYMOUS &! linux gives significant results.

Of course, you may find some systems with mmap without MAP_ANONYMOUS
but these are rare, and you can detect them with a #ifdef
MAP_ANONYMOUS (I'll be extremely surprised by systems where
MAP_ANONYMOUS exist but is not a preprocessor name).

But I am not a unix lawyer, even if I did practice several unix before

Basile STARYNKEVITCH         http://starynkevitch.net/Basile/ 
email: basile<at>starynkevitch<dot>net 
aliases: basile<at>tunes<dot>org = bstarynk<at>nerim<dot>net
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