[GHC] #13237: Extend TH with addModCStub

[GHC]

#13237: Extend TH with addModCStub
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        Reporter:                    |                Owner:
  facundo.dominguez                  |  facundo.dominguez
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:  8.2.1
       Component:  Template Haskell  |              Version:  8.0.1
      Resolution:                    |             Keywords:  inline-c
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3106
       Wiki Page:                    |
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Comment (by facundo.dominguez):

 Suppose we compile this module.
 {{{
 module A where

 do addCStub "#include \"header.h\""
    return []
 }}}

 How does GHC know to recompile `A.hs` when `header.h` changes.

 Yes, the hash in `A.hi` includes the old contents in `header.h`, but that
 doesn't seem to cause GHC to notice that `header.h` changed.

 For the use case of inline-c, `addCStub` doesn't need to do more. The user
 won't call it directly. But if you know of other use cases it would be
 great to learn of them.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13237#comment:15>
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