mmap/munmap with zero length
Alexander Best
alexbestms at math.uni-muenster.de
Sun Jul 5 07:32:28 UTC 2009
so mmap differs from the POSIX recommendation right. the malloc.conf option
seems more like a workaround/hack. imo it's confusing to have mmap und munmap
deal differently with len=0. being able to succesfully alocate memory which
cannot be removed doesn't seem logical to me.
alex
Nate Eldredge schrieb am 2009-07-05:
> On Sun, 5 Jul 2009, Alexander Best wrote:
> >i'm wondering why mmap and munmap behave differently when it comes
> >to a length
> >argument of zero. allocating memory with mmap for a zero length
> >file returns a
> >valid pointer to the mapped region.
> >munmap however isn't able to remove a mapping with no length.
> >wouldn't it be better to either forbid this in mmap or to allow it
> >in munmap?
> POSIX has an opinion:
> http://www.opengroup.org/onlinepubs/9699919799/functions/mmap.html
> "If len is zero, mmap() shall fail and no mapping shall be
> established."
> http://www.opengroup.org/onlinepubs/9699919799/functions/munmap.html
> "The munmap() function shall fail if:
> ...
> [EINVAL]
> The len argument is 0."
> --
> Nate Eldredge
> neldredge at math.ucsd.edu
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