Alternative libio vtable hardening approach

[Pedro Alves]

On 06/03/2016 10:44 AM, Florian Weimer wrote:

> This will need an additional substraction in the validation code because
> there is no relocation to express the different between two pointers,
> even though this value is a link-time constant.  The statically sized
> array makes the difference a constant, avoiding this problem.

Is it a problem in practice?
> 
> (GCC currently does not perform this optimization for pointer
> differences, but it's easy enough to do it manually.)

I believe it would sort out the "static link now pulls
everything" issue mentioned downthread, though.

Thanks,
Pedro Alves