#2999: yi darcs crashes ghc 6.11.20090201
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Reporter: wolverian | Owner: chak
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 6.11
Severity: normal | Resolution:
Keywords: xen, linux, yi | Testcase:
Os: Linux | Architecture: x86_64 (amd64)
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Changes (by chak):
* owner: => chak
Comment:
On second thought, it's not really important whether it happend in 6.10.1.
You should see this problem '''only''' when you use a version of GHC that
has been compiled with debugging (of the compiler) enabled - i.e., the
compiler was compiled with `-DDEBUG`.
Due to an infelicity in the type checker, some type variables (represented
by IORefs) are currently updated twice in certain contexts. This is
usually a harmless -if annoying- problem as the type variable should be
updated twice with the same type term. However, a debugging compiler has
assertions that catch repeated updates, which is why you see this panic.
We have been planning to clean up the relevant code (by using side effects
less liberally than they are at the moment - surely a Good Thing!), but it
involves quite a bit of code rewriting, which is why it hasn't happend
yet. For the moment, I can only suggest to use a compiler that hasn't
been compiled with `-DDEBUG`.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2999#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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