Another CPP gotcha for the manual

Simon Marlow marlowsd at
Tue Nov 5 08:41:30 UTC 2013

cpphs would be *another* GPL dependency.  It doesn't replace gcc, which 
we need for other reasons, so at the time adopting cpphs didn't solve 
any problems.  Now, arguably it would.

I'd still prefer not to add another GPL dependency(*).  But I'm not 
going to argue strongly against it.  If we're seriously considering 
using cpphs, we should carefully measure the impact on compilation time.


(*) For the pedants, yes I know the difference between GPL and LGPL and 
the difference between library and executable dependencies.  I was a 
pedant once too :-)

On 04/11/2013 09:52, Malcolm Wallace wrote:
> AFAIK, it is solely the (L)GPL licence issue.  GHC central preferred to use/distribute the GPL'd gcc compiler rather than the GPL'd cpphs preprocessor.  (No, it made no sense to me either.)
> Regards,
>      Malcolm
> On 4 Nov 2013, at 09:40, Herbert Valerio Riedel wrote:
>> Hello Malcolm,
>> On 2013-11-04 at 10:28:27 +0100, Malcolm Wallace wrote:
>>> Of course, cpphs solved this problem nearly a decade ago.
>> Btw, what has been the reason it hasn't been adopted as bundled `cpp`
>> replacement in the GHC distribution in the past? (if it remains a
>> separate executable, its GPL licence shouldn't be an issue -- after all,
>> ghc relies on the gcc executable which is GPL'ed too)
>> cheers,
>>   hvr
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