[GHC] #12558: GHCi Segmentation fault/access violation in generated code

[GHC]

#12558: GHCi Segmentation fault/access violation in generated code
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           Reporter:  lazac   |             Owner:
               Type:  bug     |            Status:  new
           Priority:  normal  |         Milestone:
          Component:  GHCi    |           Version:  8.0.1
           Keywords:          |  Operating System:  Windows
       Architecture:  x86     |   Type of failure:  GHCi crash
          Test Case:          |        Blocked By:
           Blocking:          |   Related Tickets:
Differential Rev(s):          |         Wiki Page:
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 GHCi crashes with the error message `Segmentation fault/access violation
 in generated code`. The problem arises when trying to use the
 [https://github.com/haskell-tools/haskell-tools Haskell Tools project]
 from GHCi. The program can be successfully compiled with the ghc compiler.

 The cause of this behavior is that there are elements thats type is
 computed by a type family application. When I changed the representation
 to eliminate these, the problem was gone.

 I can turn the problem on and off only by adding an import or removing it.
 To solve the problem simply comment out the modules that use the
 information with the complex calculated type, as done in the attached
 diff.

 To try out use a minimal program:

 {{{#!hs
 module Main where

 import Language.Haskell.Tools.Refactor

 main = demoRefactor "" "." "A"
 }}}

 Execute the `ghci -package ghc -isrc\ast;src\ast-ghc;sr
 c\ast-trf;src\ast-ppr;src\ast-gen;src\refactor;src Main` command from the
 project root.

 That will search for a simple `A.hs` file in the working directory. A
 minimalistic module is enough to trigger the problem:

 {{{#!hs
 module A where
 }}}


 PS: I tried to create a smaller example, but the problem just appears and
 disappears without "reason" when I try to modify the code. (For example
 importing a module that is not actually used.)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12558>
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