Stuff Michael Meeks is doing

E-mail pokeage. Projector arrived - tested that, looks good. News from India, of news in the UK, sigh seemingly more twisted people. Released ooo-build-1.9.114.
Started a random analysis of 30 or so relocations of an un-doctored libsvx - just amazing to see the size & expense of the vtable construction of the deep C++ inheritance that OO.o goes in for.
Sat and thought about the stupid vtable construction approach, and it's total lack of lazy / caching behavior. After some considerable thought came up with a crazy design: we can reduce the vtable (unique symbol-driven) relocation cost (in one potential implementation) to ~1 relocation per vtable: by forcing a common register for the vtable-offset logic; eg.
```
        movl <vtable-offset>(%eax), %edx
        call *%edx
           ->  lazy_link_vtable_method(this, ...);
                 int offset = %edx - this->vtable;
		 *(this->vtable + offset) = lookup_plt_style_sym(
			this->plt_style_syms[offset]);
		call %edx
	   <-
```
Thus using the vtable itself in place of PLT like slots, giving a cost of: a fixed invocation register, N-duplicate symbol relocations to intialize the vtables [fixable] later, & storage for them, & storage for the symbol references to resolve the vtable later in place of the original relocations. Should be backwards compatible at least. Michael Matz warns of possible fn. pointer comparison problems - true enough; wonder what the spec. says about that. Need to measure the real number of vtable related relocations in OO.o first.
Dinner, status report - set to tidying up (at least slightly) the fearsome mess in the loft. For some reason my home is green.

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Stuff Michael Meeks is doing

2005-07-07: Thursday