[GHC] #12492: internal error: allocation of 1048608 bytes too large

[GHC]

#12492: internal error: allocation of 1048608 bytes too large
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           Reporter:  erikd          |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.0.2
          Component:  Runtime        |           Version:  8.0.1
  System                             |
           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'm getting this error error when trying to use the `ghc-datasize` package
 from Hackage to calculate the in memory size of a data structure. The full
 error is:

 {{{
 load-test: internal error: allocation of 1048608 bytes too large (GHC
 should have complained at compile-time)
     (GHC version 8.0.1 for x86_64_unknown_linux)
     Please report this as a GHC bug:
 http://www.haskell.org/ghc/reportabug
 }}}

 However, this message is bogus because this is not a static data structure
 known at compile time, but data loaded from disk. Currently, my test
 program just loads this complex data structure (about 27 megabytes of CSV
 with embedded JSON on disk) into memory and then calls `recursiveSize`
 from `GHC.Datasize` on it. I get this same error message with both
 ghc7.10.3 and ghc-8.0.1.

 If I remove the call to `recursiveSize` there is no error.

 If I `Control.Deepseq.force` the data structures before calling
 `recursiveSize` there is no error.

 So, who is to blame? `ghc-datasize` is just Haskell code that calls public
 APIs so I think the blame lies with GHC.

 I'll work on getting a small re-producable test case.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12492>
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