Re: [GHC] #16095: Infinite loop during error reporting (ignores SIGINT/SIGTERM, then OOMs) (was: Infinite loop during error reporting (unkillable, OOM))

25 Dec 2018

      #16095: Infinite loop during error reporting (ignores SIGINT/SIGTERM, then OOMs)
-------------------------------------+-------------------------------------
        Reporter:  _deepfire         |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.1
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Description changed by _deepfire:

Old description:
...
Compiling the repro snippet produces the following incomplete output and
hangs GHC:
{{{
$ ghc repro.hs
[1 of 1] Compiling Main             ( repro.hs, repro.o )
repro.hs:16:22: error:
}}}
The GHC process then ignores Ctrl-C -- so it must be killed with SIGKILL.
This minimal snippet depends on `generics-sop` (tested with version
`0.4.0.0`).
Sadly I didn't find a constraint in `base` to cause this behavior..
{{{#!hs
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TypeFamilies #-}
import Generics.SOP (HasDatatypeInfo)
data family   TF i a :: *
data instance TF i a = R
class C i a where
  method :: TF i a
instance C i () where
instance HasDatatypeInfo a => C i a where
  method = undefined function
function :: C i a => TF i a
function = method
main = undefined
}}}
New description:

 Compiling the repro snippet produces the following incomplete output and
 hangs GHC:
 {{{
 $ ghc repro.hs
 [1 of 1] Compiling Main             ( repro.hs, repro.o )

 repro.hs:16:22: error:
 }}}

 The GHC process ignores SIGINT -- so it must be killed with SIGKILL.
 The memory usage grows, until it consumes all memory (~30G RAM + swap) and
 is terminated by the OOM killer.

 This minimal snippet depends on `generics-sop` (tested with version
 `0.4.0.0`).
 Sadly I didn't find a constraint in `base` to cause this behavior..

 {{{#!hs
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE TypeFamilies #-}

 import Generics.SOP (HasDatatypeInfo)

 data family   TF i a :: *
 data instance TF i a = R

 class C i a where
   method :: TF i a

 instance C i () where

 instance HasDatatypeInfo a => C i a where
   method = undefined function

 function :: C i a => TF i a
 function = method

 main = undefined
 }}}

--

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16095#comment:1
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler