Simon Marlow | 5 Apr 21:51 2011
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Re: Rebuilding ghc changes interface hashes?

On 05/04/11 17:51, Matthias Kilian wrote:
> On Tue, Apr 05, 2011 at 09:59:23PM +0530, Joachim Breitner wrote:
>> Also, the initial upload was built using ghc-6.12.1, while the upload
>> now is build with ghc-7.0.2. Given that it is a two-stage compiler, I
>> assume that the output should be identical, but it seems not to be the
>> case.
>
> Changing the bootstrapping compiler changes the ABIs. The same can
> happen if you interrupt and restart the build.

In general changes can creep in randomly, there's no direct link between 
changing the bootstrap compiler and getting different compilation 
results (as far as I know), but there are some small elements of 
randomness.  I did manage to squash most causes of this, but a couple 
remain, see

http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/RecompilationAvoidance#Interfacestability

there may be others that I don't know about.

I would really like to fix this, I'll think about whether we can make a 
deterministic sort-order for bindings in Core, that would fix the CSE issue.

Cheers,
	Simon

> http://hackage.haskell.org/trac/ghc/ticket/4012
>
> Ciao,
> 	Kili
>
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Gmane