[Bug libc/6816] Support for POWER7 VSX registers in *context routines

["drepper at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

------- Additional Comments From drepper at redhat dot com  2008-10-16 17:05 -------
(In reply to comment #19)
> That is true for getcontext but may not be true for set/swapcontext depending on
> the source of the context (ie. signal frames).
> 
> So it seem like the setcontext and the kernels swapcontext syscall should handle
> the larger context size. 

That has never been supported.  If it happened to work on ppc then this is
rather an accident.

Changing the data structure is hell.  It cannot be handled using versioning or
any other method complete without explicitly adding version information into the
data structure.  This would have to be in a completely backward compatible way.
 I.e., the version value would have to be in the range of the original data
structure and there must not be any ambiguity (i.e., you have to find a byte or
four in the original structure which has a limited range and use one of the
value which _never_ can happen in the real world).

And even that will not solve the problem of getcontext() where the data
structure can be uninitialized.  There really is no complete solution.

Hence, making such unnecessary changes just for the purpose of some programs
using undefined behavior is complete madness.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6816

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