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SubjectRe: shmat problem
Doug McNaught, Mon, Jan 06, 2003 17:50:24 +0100:
> > Linux manpages-1.54 (Dec 30 2002):
> >
> > The (Linux-specific) SHM_REMAP flag may be asserted in shmflg to indi-
> > cate that the mapping of the segment should replace any existing map-
> > ping in the range starting at shmaddr and continuing for the size of
> > the segment. (Normally an EINVAL error would result if a mapping
> > already exists in this address range.) In this case, shmaddr must not
> > be NULL.
>
> Wouldn't the OP's code still (potentially) have problems? What if you
> had:
>
> char my_shared_area[2048];
> int my_unshared_var;
>
> void *foo = shmat(id, &my_shared_area, SHM_REMAP);
>
> Would my_unshared_var end up shared, since memory mappings have page
> granularity?
>

yes, i suppose so.
Maybe that was the reason making SHM_REMAP non-default
behaviour for shmat.

-alex
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