[GHC] #8683: add "cpp program" and "cpp program options" to settings file

[GHC]

#8683: add "cpp program" and "cpp program options" to settings file
-------------------------------------+------------------------------------
        Reporter:  carter            |            Owner:
            Type:  feature request   |           Status:  new
        Priority:  normal            |        Milestone:  7.8.1
       Component:  Compiler          |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:  #8439
-------------------------------------+------------------------------------

Comment (by carter):

 heres my current notes, which sort of restate my prior comment

 NOTES

 from config.mk.in
 {{{
 CONTEXT_DIFF        = @ContextDiffCmd@
 CP          = cp
 # It's not easy to separate the CPP program from its flags, as
 # AC_PROG_CPP defines CPP as "/usr/bin/gcc -E"
 CPP         = @CPP@ @CPPFLAGS@
 #
 # RAWCPP_FLAGS are the flags to give to cpp (viz, gcc -E) to persuade it
 to
 # behave plausibly on Haskell sources.
 #
 # Clang in particular is a bit more annoying, so we suppress some
 warnings.
 RAWCPP_FLAGS            = -undef -traditional
 ifeq "$(CC_CLANG_BACKEND)" "1"
 RAWCPP_FLAGS           += -Wno-invalid-pp-token -Wno-unicode -Wno-
 trigraphs
 endif
 }}}

 RAWCPP is then used in compiler/ghc.mk  to define

 {{{
     @echo 'cRAWCPP_FLAGS         :: String'                             >>
 $@
     @echo 'cRAWCPP_FLAGS         = "$(RAWCPP_FLAGS)"'                   >>
 $@
 }}}

 which is then used in  compiler/main/SysTools.lhs to do
 {{{
   234         gcc_prog <- getSetting "C compiler command"
   235:        gcc_args_str <- getSetting "C compiler flags"
   ....

        let cpp_prog  = gcc_prog
 289             cpp_args  = Option "-E"
 290                       : map Option (words cRAWCPP_FLAGS)
 291:                     ++ gcc_args
 }}}
 and then intiizes (still in SysTools)
 {{{
                    sPgm_P   = (cpp_prog, cpp_args),
 }}}

 then in compiler/main/DynFlags.hs
 {{{
     1807: setPgmP   f = let (pgm:args) = words f in alterSettings (\s -> s
 { sPgm_P   = (pgm, map Option args)})
 }}}

 and then still in compiler/main/DynFlags.hs
 {{{
      2144:   , Flag "pgmP"           (hasArg setPgmP)
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8683#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler