odd GHC 6.8.2 compile failure

Simon Marlow simonmarhaskell at gmail.com
Fri Jan 4 09:43:15 EST 2008

Isaac Dupree wrote:
> Simon Marlow wrote:
>> Note however that if you install this compiler, the packages in your 
>> home directory won't work any more, because they were compiled by 
>> another instance of 6.8.2
> true, but doesn't 6.8.2 itself have the same ABI as any other 6.8.2, not 
> counting packages?

Yes, the ABI is the same, but there's no guarantee that the interfaces to 
all the packages are the same.

>> against a different set of packages.
> hmm.  different versions?  I think it might work out since I installed 
> everything locally, if I just install the versions of the extra-libs 
> that came with the 6.8.2 bindist...
> Or do I have too great hopes in the reproducibility of ghc compilations?

It's too fragile to rely on getting the same results when you compile a 
package again, if -O is on.  In practice, if the conditions are exactly the 
same you can often get identical interfaces, but we've never put any effort 
into figuring out how to guarantee this and under what conditions.  Better 
not to rely on it.


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