Re: Binary format of compiler

On Sep 13, 2004, at 3:14 AM, Vesa A Norrman wrote:

> Hello, since the latest working version sometimes has bugs, a good way 
> to install compiler would be:
> 1. run config/install.sh
> 2. get compiler source
> 3. fix bug in source
> 4. CMB.make (), makeml, installml
> 5. rerun config/install.sh
> (Like Matthias said in a message in March.)
> The step 5. was necessary to synchronize libraries. Does this mean 
> that compiling the compiler changes binary format of libraries?
> Vesa

The short answer is: yes.  The longer answer is that it has to do with 
how persistent stamps (which uniquely
identify individual compilation units) are generated.  Aside from a 
hash of the unit's interface, a number
of random bits are thrown into the mix to generate each stamp.  This is 
necessary to avoid confusing
modules that have identical interfaces. (Otherwise one could subvert 
abstractions guaranteed by the type
system.)

Those random bits are cached in the file system to avoid needless 
recompilations.  Unfortunately, the bits are
not shipped with the bootfiles, so when you do CMB.make() you end up 
generating fresh random bits which
differ from those that were used when we generated the bootfiles.  As a 
result, all modules appear to change their
identity -- which makes it necessary to recompile libraries that depend 
on them.

Matthias



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