Notes on building 6.10.1

[Gregory Wright]

Hi,

When building 6.10.1 under Macports, I noticed that hpc now requires  
that hsc2hs
be present on the system (it does not use the hsc2hs built in place  
with the new ghc).
Previous versions did not require hsc2hs to be present; the compiler  
could be
bootstrapped from just the ghc compiler and ghc-pkg.

The hpc library is the only one that requires the external hsc2hs.  Is  
this new dependency
intentional, or is this a build system bug?

This problem escaped detection initially because cabal will use any  
hsc2hs on the path
even if the --with-compiler flag is set.  (--with-compiler forces a  
particular compiler and
packaging program, but not hsc2hs.)  This is just asking for trouble.   
For the moment,
it's fixed in the Macports build by hacking hpc's Makefile to specify  
--with-hsc2hs.

Should cabal produce and error or a warning if hsc2hs is not found in  
the same directory
as the compiler?  I suggest an error by default, but not if --with- 
hsc2hs is given explicitly.

Best Wishes,
Greg