Re: [RFC] POSIX personality

[jw schultz]

On Thu, May 23, 2002 at 10:09:28AM -0700, Linus Torvalds wrote:
> 
> 
> On Thu, 23 May 2002, Bill Davidsen wrote:
> >
> > I think the reason which comes to mind is avoiding future problems. By
> > having a single POSIX mode flag not only does the program not have to know
> > about setting the "right" other bits today, but if we find that POSIX
> > behaviour is needed in some other area in the future, the program doesn't
> > need to be modified and recompiled, because the POSIX behaviour "is in
> > there" for all things.
> 
> That's a nice argument in theory, but if you change the behaviour of
> existing flags, you might fix some program for the real semantics, but you
> might equally well _break_ some program that unwittingly depended on the
> old semantics.
> 
> So I think your argument is fundamentally flawed. The binary has been
> tested with the old behaviour, and assuming that you can "fix" existing
> binaries by changing kernel behaviour is a seriously flawed argument.
> 
> Yes, it might work for some programs, but basically you're on very thin
> ice.
> 
> Does Linux break stuff when absolutely required? Sure. But designing an
> interface that _plans_ on changing semantics is just incredibly stupid,
> and should absolutely not be done. Ever.
> 
> 			Linus

It seems to me that the biggest issue here is maintaining
POSIX behavior without having to modify application source
every time the flag set changes.

Perhaps a POSIX bitmask could be defined.

For a degree of binary compatibility a few unused flags
could be reserved and the POSIX bitmask include them
whether they had meaning yet or not. 

-- 
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	J.W. Schultz            Pegasystems Technologies
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