PCH and exec-shield...

[Mike Stump]

On Monday, March 8, 2004, at 01:04 PM, Mark Mitchell wrote:
> There is a more general approach used by other PCH implementations 
> which involves walking the loaded PCH and swizzling pointers.  That 
> would be a superior approach as it would make PCH more robust on all 
> platforms, and would permit people to use exec-shield randomization 
> (and similar features on other operating systems) with PCH.
>
> Until that is implemented, many people will probably complain that PCH 
> is broken.

Using a feature that serves no purpose other than to slow down 
compilations can reasonably be considered a bug.  By having PCH swizzle 
on load, we permit the introductions of bugs into the compiler.  This 
is bad.  This is why it hasn't been done.

For robustness we should fall back to the normal .h file and pretend 
the PCH file doesn't exist.  I think we might just give a sorry now, 
that might be wrong.

We may one day have a reason to swizzle on load, but I don't think 
we've found it yet.