[GHC] #14998: Sort out the strictness mess for exceptions

[GHC]

#14998: Sort out the strictness mess for exceptions
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        Reporter:  simonpj           |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.3
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:  Exceptions
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by sgraf):

 Re Item 2: A net loss (0.2% Allocs, 0.1% Instr). `reverse-complement`
 allocates 11.6% more, `sphere` executes 4.4% more instructions, `binary-
 trees` 0.9% less.

 This was the diff:

 {{{
 diff --git a/libraries/base/GHC/IO.hs b/libraries/base/GHC/IO.hs
 index 118ebea..554b4e3 100644
 --- a/libraries/base/GHC/IO.hs
 +++ b/libraries/base/GHC/IO.hs
 @@ -142,7 +142,7 @@ have to work around that in the definition of catch
 below).
  -- @catchException undefined b == _|_ at . See #exceptions_and_strictness#
  -- for details.
  catchException :: Exception e => IO a -> (e -> IO a) -> IO a
 -catchException !io handler = catch io handler
 +catchException io handler = catch io handler

  -- | This is the simplest of the exception-catching functions.  It
  -- takes a single argument, runs it, and if an exception is raised
 @@ -194,7 +194,7 @@ catch (IO io) handler = IO $ catch# io handler'
  -- @catchAny undefined b == _|_ at . See #exceptions_and_strictness# for
  -- details.
  catchAny :: IO a -> (forall e . Exception e => e -> IO a) -> IO a
 -catchAny !(IO io) handler = IO $ catch# io handler'
 +catchAny (IO io) handler = IO $ catch# io handler'
      where handler' (SomeException e) = unIO (handler e)

  -- Using catchException here means that if `m` throws an
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14998#comment:6>
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