[GHC] #9839: RTS options parser silently accepts invalid flags

[GHC]

#9839: RTS options parser silently accepts invalid flags
-------------------------------------+-------------------------------------
       Reporter:  adamgundry         |                   Owner:  simonmar
           Type:  bug                |                  Status:  new
       Priority:  normal             |               Milestone:
      Component:  Runtime System     |                 Version:  7.8.3
       Keywords:                     |        Operating System:
   Architecture:  Unknown/Multiple   |  Unknown/Multiple
     Difficulty:  Unknown            |         Type of failure:  Incorrect
     Blocked By:                     |  result at runtime
Related Tickets:  #4243              |               Test Case:
                                     |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------
 RTS options that do not take arguments (such as `-T`) silently ignore
 anything that comes afterwards. For example, `+RTS -T,-s` or `+RTS -T-s`
 turns on collection of GC statistics (`-T`) but does not print out a
 summary (`-s`). Instead, this should produce an error message. Otherwise,
 users may mistakenly think that options have been applied.

 (This has just bitten us in a production system.)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9839>
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