[GHC] #10531: modules that can be linked successfully when compiled with optimizations, fail to link with: multiple definition of `__stginit_ZCMain'

[GHC]

#10531: modules that can be linked successfully when compiled with optimizations,
fail to link with: multiple definition of `__stginit_ZCMain'
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        Reporter:  imz               |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  normal            |               Milestone:
       Component:  Compiler          |                 Version:  7.6.1
      Resolution:                    |                Keywords:
Operating System:  Linux             |            Architecture:  x86_64
 Type of failure:  GHC rejects       |  (amd64)
  valid program                      |               Test Case:  attached
      Blocked By:                    |                Blocking:
 Related Tickets:                    |  Differential Revisions:
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Comment (by ezyang):

 The manual suggests that recompilation checking doesn't really work with
 `-main-is`:
 https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/options-
 phases.html (the problem being that when you build `B.hs` the second time,
 it needs to recompile `A.hs` with a DIFFERENT `-main-is` flag.)

 But it sort of looks like dterei tried to fix this in #437, so maybe this
 was intended to be fixed, and the manual wasn't updated? In any case, this
 looks like a fine bug to me. Once fixed the admonition from the manual
 should be removed.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10531#comment:1>
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