Fundamental defect of the concept of shared libraries

[Guy Harris]

>If we take 1), the hardware architecture must support PC relative jump,
>of course. Moreover, to access library private data, it must also
>address data PC relative. Aside from effeciency, not all architechture
>support this.

Are there any architectures of interest in this discussion that can't
support PC-relative references?

>Even worse, with some architechture, it is impossible to map several virtual
>addresses to a physical address. Virtually tagged cache and inverted
>page tables are notable examples.

If you believe that a system with a virtual-address cache, or a system
with inverted page tables, cannot map several virtual addresses to a
physical address, you're wrong.  Proof by counterexample:

	1) various flavors of Suns with virtual address caches, which
	   all support mapping several virtual addresses to a physical
	   address;

	2) the IBM ROMP and RIOS architectures, which have inverted page
	   tables and support mapping several virtual addresses to a
	   physical address.

They may have to go through some amount of pain to do so, but they *do*
manage to do it.