[GHC] #14769: The RecompBecause [TH] check is not resume-build-safe

[GHC]

#14769: The RecompBecause [TH] check is not resume-build-safe
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        Reporter:  nh2               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #481              |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonmar):

 > but so far I haven't found a reason why maintaining an independent
 "seed" for each module (as we know all modules ahead of time in a --make
 invocation) wouldn't cover at least the cases of multiple modules and -j.

 But what are those seeds? The unique supply for each module would need to
 generate uniques that are
 - different from those in every other module
 - the same each time you compile this module

 So it seems like the uniques would have to be qualifed by the
 module/package names somehow. Or did you have some other idea in mind?

 > Regarding the lazy I/O in the typechecker, could you point me at where
 that happens?

 Look at `TcRnMonad.forkM_maybe`.

 If you solved the seed problem (above) then the same solution could be
 applied to unique supplies for imported modules which would also solve the
 lazy I/O problem, but it's still not clear to me how you do this.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14769#comment:6>
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