The haddock / clang problem revisited ... root cause found...

Mark Lentczner mark.lentczner at
Wed Jul 23 14:20:47 UTC 2014

*Re.: Full details here: Root cause of haddock / clang failure

Iain Nicol had submmited a set of commits back in May which addressed the
"double pre-process" issue with Haddock. No one had figured out the
connection to this set of issues with clang back then.

I back-ported them to 1.18 last night
<>, verfied that these patches do
indeed fix the issue, and Johan has committed them to the tree.

My plan is to ship haskell platform with Cabal- (forthcoming),
which is just these patches beyond the Cabal- that comes with GHC
7.8.3. This will just be an additional version of the Cabal package, in the
package db that ships with the platform. I won't re-build 7.8.3 with a
patched Cabal. I don't think there will be any major issues(*) with users
getting a package db with two Cabal versions (cabal-install will be built
against the later one).

- Mark

(*) If some proejct depends on package ghc and Cabal, then they will get (as that is what ghc, in 7.8.3 is compiled against in the official
bindist). If that project then invokes the haddock operation ... it will
double pre-process input if EnableExtension CPP is in allExtensions of the
project they are building. I think we're safe...
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