[GHC] #13330: forkIO has inconsistent behavior under optimization

[GHC]

#13330: forkIO has inconsistent behavior under optimization
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        Reporter:  dfeuer            |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Core Libraries    |              Version:  8.1
      Resolution:  fixed             |             Keywords:  Exceptions
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3189
       Wiki Page:                    |
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Comment (by simonpj):

 I'm looking at this exception-semantics stuff again,
 as I try to make sense of the nested CPR stuff #1600 and Phab:D4244.

 I'm puzzled.

 * The strrictness analyser has quite a bit of complexity around
 `ThrowsExn`.
 * `ThrowsExn` only differs from `Diverges` if the `ExnStr` flag is set to
 `ExnStr`
 * And the only place that happens is in `Demand.catchArgDmd`
 * The only place `catchArgDmd` is used is in `primops.txt.pp`.
 Originally, in the patch for #11222, `catchArgDmd` was used for the first
 arg of `catch#`, `catchSTM#` and `catchRetry#`.
 * But the patch in this ticket removed two of those three; now only
 `catchRetry#` uses the `catchArgDmd` thing.

 It loosk t me as if `catchRetry#` was left out by mistake.  Right, David?

 And if so, that's the last use of `catchArgDmd` and I think that all the
 tricky `ThrowsExn` machinery can disappear.

 Incidentally, here's the amazing history of the strictness of `catch#`

 * Dec 13: 0558911f91c: catch# gets a strictness signature with
 `lazyApply1Dmd`
 * Jul 15: 7c0fff41789: catch# goes from `lazyApply1Dmd` to
 `strictApply1Dmd`
 * Dec 15: 28638dfe79e: catch# goes from `strictApply1Dmd` to
 `lazyApply1Dmd`.  Trac #10712
 * Jan 16: 9915b656440: catch# goes from `lazyApply1Dmd` to `catchArgDmd`,
 and result goes from `botRes` to `exnRes`  Trac #11222.
 * Mar 17: 701256df88c: catch# goes from 'catchArgDmd` to `lazyApply1Dmd`.
 This ticket #13330.

 See also `Note [Strictness for mask/unmask/catch]` in `primops.txt/pp`.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13330#comment:20>
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