[GHC] #15038: Memory Corruption (strange closure type)

15 Apr 2018

      #15038: Memory Corruption (strange closure type)
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           Reporter:  andrewthad     |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.4.1
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 I've been encountering corruption of memory in a library of mine that uses
 some of GHC's more recent features (levity polymorphism and unboxed sums).
 The library is `packed`, and it's source code can be found on my github.
 But, more relevant to this issue is the minimal reproducible example I've
 put together here: https://github.com/andrewthad/corrupted-memory-example

 It's still a bit larger than I'd like it to be, and if no one has any
 insights into this, I can keep whittling it down to make it more minimal.
 Here's how to run it:

 {{{
 git clone https://github.com/andrewthad/corrupted-memory-example
 cd corrupted-memory-example
 cabal new-build --enable-tests test
 ./dist-newstyle/build/corrupted-memory-example-0.1/build/test/test
 }}}

 This consistently crashes with:

 {{{
 test: internal error: evacuate(static): strange closure type 16648
     (GHC version 8.4.1 for x86_64_unknown_linux)
     Please report this as a GHC bug:
 http://www.haskell.org/ghc/reportabug
 }}}

 Additional information: This issue can be reproduced using GHC 8.2.2, GHC
 8.4.1, and GHC HEAD. This project cannot be built with GHC 8.0.2 and
 earlier since it uses unboxed sums. Building this project with either
 `stack` or `cabal new-build` and then running the test causes the same
 crash. However, building it with plain old GHC and then running it does
 not. This is really weird, since there aren't any GHC options in the cabal
 file that should affect this. In the original library, I have a bunch of
 tests that use the parsers `byte` and `any` in a variety of situations,
 and none of them every trigger this crash except for the ones where I
 stick a `Parser` inside of a `Trie`. This project does a lot of manual
 passing of state tokens, but I believe all of these uses to be correct
 (mostly because of the extensive tests in the original repo, but I've also
 spent a lot of time just looking at the code to figure out if this was
 something on my end).

 Let me know if the example is too big. I can spend some more time
 shrinking it further, but I wanted to go ahead and get it up here.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15038
GHC http://www.haskell.org/ghc/
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