[GHC] #14756: `ghc -M` doesn't emit dependencies for header files included either via CPP or CApiFFI

[GHC]

#14756: `ghc -M` doesn't emit dependencies for header files included either via CPP
or CApiFFI
-------------------------------------+-------------------------------------
           Reporter:  hvr            |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.2.2
           Keywords:  capi capiffi   |  Operating System:  Unknown/Multiple
  cpp                                |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Given the following simple module

 {{{#!hs
 {-# LANGUAGE CApiFFI #-}

 #include "Bar.hs.inc"

 module Foo where

 foreign import capi unsafe "cbits.h foo" c_foo :: Int -> IO ()
 }}}

 The dependency information produced by `ghc -dep-suffix '' -M  Foo.hs` is

 {{{
 # DO NOT DELETE: Beginning of Haskell dependencies
 Foo.o : Foo.hs
 # DO NOT DELETE: End of Haskell dependencies
 }}}

 And neither mention the include header dependency `cbits.h` nor
 `Bar.hs.inc`.



 See also
 https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/separate_compilation.html
 #makefile-dependencies

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14756>
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