[GHC] #8650: Unexpected behaviour of import ccall "header.h function"

[GHC]

#8650: Unexpected behaviour of import ccall "header.h function"
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              Reporter:  nh2         |            Owner:
                  Type:  bug         |           Status:  closed
              Priority:  normal      |        Milestone:
             Component:  Compiler    |          Version:  7.6.3
            Resolution:  invalid     |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  Documentation bug                  |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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Changes (by rwbarton):

 * status:  new => closed
 * resolution:   => invalid


Comment:

 Basically, by providing the correct header file in the import
 specification, you gain portability to Haskell compilers which compile via
 C (including, but not limited to, ancient or unregisterised versions of
 GHC).

 Replying to [ticket:8650 nh2]:
 > In that case, why does
 http://www.haskell.org/onlinereport/haskell2010/haskellch8.html suggest
 {{{ccall "string.h strlen"}}}? In the other case, why would it suggest
 this if the {{{"string.h"}}} part is ignored?

 Because that is the Haskell 2010 Report, not the GHC documentation (though
 it would be accurate for unregisterised versions of GHC).

 > Relatedly, I can write
 >
 > {{{
 > foreign import ccall "some.rubbish" f :: IO ...
 > }}}
 >
 > and as long as {{{"some.rubbish"}}} contains a dot, nothin in the system
 will ever complain.

 As specified by section 8.5.1 of the Report, both the `chname` and the
 `cid` are optional. The Report does not specify how to resolve the
 resulting ambiguity, but since a C identifier cannot contain a dot, GHC
 must be treating `some.rubbish` as the header file name, and using the
 Haskell name `f` as the C identifier, as also specified by the Report:

 > If `cid` is omitted, it defaults to the name of the imported Haskell
 variable.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8650#comment:4>
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