#2987: panic when compiling again
---------------------------------+------------------------------------------
Reporter: dsrogers | Owner: igloo
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.10.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Unknown/Multiple
Architecture: Unknown/Multiple |
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Changes (by simonpj):
* owner: => igloo
Comment:
Simon and I investigated. There are two different things going on.
* First, Cabal triggers a complete rebuild for `cabal install` because
Cabal gives different package flags to GHC in `cabal build` and `cabal
install`. This is because its package-planning algorithm is different in
the two cases. Apparently this infelicity has now been fixed.
For reasons I don't fully understand, Cabal doesn't always do this; it
broke for Simon M, but did not break for me, although we were using the
exact same GHC.
* However, GHC should not crash, regardless. Turns out that it was
tricky consequence of this patch:
{{{
Tue Feb 5 16:55:07 GMT 2008 [email protected]
* Inject implicit bindings before the simplifier (Trac #2070)
}}}
This patch was an unequivocally bad idea. I reversed it in the HEAD a few
weeks back, and commented why in `Note [Injecting implicit bindings]` in
`TidyPgm`. I fixed #2070 in a different way:
{{{
Fri Jan 2 14:28:51 GMT 2009 [email protected]
* Make record selectors into ordinary functions
}}}
So I think the bug should not happen in the HEAD. For the 6.10 branch I
suggest that we simply reverse the above patch ''on the branch only''; it
was only an optimisation thing anyway.
Ian, would you like to do that? It's a bit hard to test whether it fixes
the bug, because of the delicacy about Cabal above. I'd settle for just
reversing the patch and checking that the branch still validates.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2987#comment:3>
GHC <http://www.haskell.org/ghc/>
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