Status of GHC runtime dependency on GNU multi precision arithmetic library

Duncan Coutts duncan.coutts at
Thu Aug 16 10:27:57 EDT 2007

On Thu, 2007-08-16 at 14:22 +0100, Brian Hulley wrote:

> > Sounds to me like the simlest solution for you would be if GHC could use
> > a dynamically linked gmp.dll on Windows. That also sounds like much less
> > work that replacing gmp completely.
> This would certainly make things easier though it doesn't solve every 
> problem. For example, the LGPL requires you to give permission to people 
> to reverse engineer your application, in order for them to be able to 
> understand it enough to get it to work with an updated version of the 
> LGPL component. Although this is perfectly reasonable imho, it leaves me 
> with a problem if my application also needs to make use of eg Microsoft 
> runtime components or third party proprietary statically linked 
> libraries since there are parts of my program binary for which I do not 
> have the authority to grant permission to reverse engineer thus it may 
> not even be possible for me to comply with the terms of the LGPL.

>From the LGPL v3:

        You may convey a Combined Work under terms of your choice that,
        taken together, effectively do not restrict modification of the
        portions of the Library contained in the Combined Work and
        reverse engineering for debugging such modifications, if you
        also do each of the following:
        [list of stuff you have to do]

So it looks like you only have not restrict reverse engineering for the
purposes of making updated GMP libs work with your program. Since the MS
Runtime components do not interact directly with the GMP at all you
shouldn't need to grant users the right to reverse engineer those
components. Indeed it's only ghc library and rts code that would
interact with gmp.dll.

BTW, I don't think it should be too hard to construct a notice that
indicates that portions of the work are covered by specific copyright
licences, the details of which are available. After all Microsoft have
dozens of these notices for various bits of BSD code they use and nobody
mistakes Windows for Free software.

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