GHC should compile cleanly with clang

I'm running into several difficulties (which I'll catalog shortly) building GHC HEAD with Clang 3.2. These mostly seem to be difficulties relating to the preprocessor and the fact clang does not really respect -traditional-cpp mode, and that it is stricter than gcc about whitespace and whatnot too. This means code like:

{-# RULES

 "thing" ...

  #-}

becomes invalid: clang is strict about the fact that preprocessor definitions must occur on the beginning of a line. There seems to be a bug in the preprocessor directive source code to this effect (that it doesn't handle whitespace before a directive.) It's quite unfortunate, because we do this a lot.

This also causes build failures in the parser due to some crazy CPP hackery we do. I'll follow up with that shortly.

As a workaround, we may have to force CPP to just continue being cpp which will Do The Right Thing, while CC will use clang instead. Or we'll have to have some script that seds whitespace out or something.

This currently blocks #7602 since I can't test my fix otherwise.

Trac metadata

Trac field	Value
Version	7.7
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking	#7602
CC
Operating system
Architecture