[GHC] #14736: unknown opcode in interpretBCO doesn't cause process termination in some circumstances

[GHC]

#14736: unknown opcode in interpretBCO doesn't cause process termination in some
circumstances
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           Reporter:  alpmestan         |             Owner:  (none)
               Type:  bug               |            Status:  new
           Priority:  normal            |         Milestone:
          Component:  Compiler          |           Version:  8.4.1-alpha1
           Keywords:                    |  Operating System:  Linux
       Architecture:  Unknown/Multiple  |   Type of failure:  None/Unknown
          Test Case:                    |        Blocked By:
           Blocking:                    |   Related Tickets:
Differential Rev(s):                    |         Wiki Page:
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 As part of my work on #14675, I ended up in a situation where
 `rts/Interpreter.c:interpretBCO` falls into its default case, which just
 does this:

 {{{#!c
   barf("interpretBCO: unknown or unimplemented opcode %d",
        (int)(bci & 0xFF));
 }}}

 Which is fine. In the program from #14675, we are not processing the
 annotations with an external interpreter, the same runtime is compiling
 some module and running some code for the annotations, if my understanding
 is correct. And that process should therefore terminate.

 Except that it doesn't, not right away! And the example that uses the GHC
 API to load some simple module with an annotation just happily proceeds
 until it segfaults because `interpretBCO` didn't run to completion,
 probably therefore not pushing a suitable closure address or two somewhere
 or something along those lines.

 The expected behaviour here would be that the program crashes with the
 "unknown opcode" error message from above. So far the problem from #14675
 has only been reproduced on ubuntu 16.04 with 8.4.1 alpha1, however I
 suspect that the bug I'm describing -- the program not terminating when we
 call `barf` while running code that we will splice in some module that we
 are compiling using the GHC API -- is independent of the particular distro
 or maybe even OS? Not sure, I haven't looked into that.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14736>
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