Chris Kuklewicz wrote:
Simon Marlow wrote:
Aha.  Text/Regex/Posix.hs is generated from Text/Regex/Posix.hsc by
hsc2hs, but this is done on the *host* rather than the *target* when
bootstrapping, and thus generates the wrong results.  If you'd run
hsc2hs on the target, then Text/Regex/Posix.hs would have been correct,
but you can't do this because hsc2hs is a Haskell program.  You could
take the .c file generated by hsc2hs on the host and compile/run it on
the target, but that's a hassle, so instead our policy is that we don't
rely on any hsc2hs-generated code for bootstrapping.

Unfortunately I broke the rules by accident when I introduced the
dependency on regex.  I can't think of an easy way to enforce the rule,
at least at the moment, since there are other hsc2hs-processed modules
that we happen to not depend on in GHC (System.Time and System.CPUTime).

Could the solution be to depend on a pure Haskell regex implementation instead
of on a regex-posix / Posix.hsc and the system regex library?

Yes, as I mentioned, ticket 1160 (http://hackage.haskell.org/trac/ghc/ticket/1160) is for replacing regex-posix with regex-tdfa, and that would fix this issue.

However, Igloo just removed the regex packages from GHC's core package set, so we don't have the problem any more.

The regex-tdfa backend could be modified to work with the regex-base in GHC 6.6
and then regex-compat could quickly be switched to use this instead of 
regex-posix.

It sounds like a good idea to switch regex-compat to depend on regex-tdfa 
anyway.

Cheers,
        Simon

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