GHCi doesn't work unregisterised

To reproduce this bug, write the following text to bug.hs.

data D = D Char deriving Show                                                                                                                                                                           
main = print f                                                                                                                                                                                          
f = D 'a'

Start ghci, and at the prompt enter :load bug.hs, then f. Instead of printing D 'a', GHCi will segfault.

This bug DOES manifest on PowerPC (running Debian/sid).
This bug DOES NOT manifest on i386 (running Debian/sid).
This bug DOES manifest when bug.hs is loaded in ghci.
This bug DOES NOT manifest when bug.hs is compiled with ghc.

Trac metadata

Trac field	Value
Version	6.4.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Linux
Architecture	powerpc

Edited Mar 09, 2019 by Simon Marlow

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GHCi doesn't work unregisterised