I'm unclear why cpphs needs to be made a dependency of the GHC API and included as a lib. Could you elaborate? (in the wiki page possibly)

Currently, GHC uses the system preprocessor, as a separate process. Couldn't we for GHC 7.12 keep to exactly that, save for the fact that by default GHC would call the cpphs binary for preprocessing, and have the cpphs binary be available in GHC's install dir somewhere?

fork()/execvce() is cheap. Certainly cheaper than the cost of compiling a single Haskell module. Can't we keep to this separate-(and-pluggable)-preprocessor-executable scheme? We'd sidestep most license tainting concerns that way.

On 8 May 2015 at 11:39, Herbert Valerio Riedel <hvriedel@gmail.com> wrote:

Hello,

On 2015-05-08 at 11:28:08 +0200, Niklas Larsson wrote:
> If the intention is to use cpphs as a library, won't the license
> affect every program built with the GHC API? That seems to be a high
> price to pay.

Yes, every program linking the `ghc` package would be affected by
LGPL+SLE albeit in a contained way, as it's mentioned on the Wiki page:

| - As a practical consequence of the //LGPL with static-linking-exception//
|   (LGPL+SLE), **if no modifications are made to the `cpphs`-parts**
|   (i.e. the LGPL+SLE covered modules) of the GHC code-base,
|   **then there is no requirement to ship (or make available) any source code**
|   together with the binaries, even if other parts of the GHC code-base
|   were modified.

However, don't forget we already have this issue w/ integer-gmp, and
with that the LGPL is in full effect (i.e. w/o a static-linkage-exception!)

In that context, the suggestion was made[1] to handle the cpphs-code
like the GMP code, i.e. allow a compile-time configuration in the GHC
build-system to build a cpphs-free (and/or GMP-free) GHC for those
parties that need to avoid any LGPL-ish code whatsoever in their
toolchain.

Would that address this concern?


 [1]: http://www.reddit.com/r/haskell/comments/351pur/rfc_native_xcpp_for_ghc_proposal/cr1cdhb

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