[GHC] #9837: Introduce a logging API to GHC

[GHC]

#9837: Introduce a logging API to GHC
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              Reporter:  rodlogic    |            Owner:
                  Type:  task        |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.8.3
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Comment (by goldfire):

 Can you describe an intended consumer of such a log?

 To my knowledge, there is no centralized logging structure, per se,
 although there are plenty of `-d` flags that dump log-like output. There
 is some central management of these flags, but I don't think there's a ton
 of consistency about this. However, before trying to shore this up, it
 would be helpful to know what a consumer would look like.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9837#comment:3>
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