[GHC] #11231: GHC's configure script does not honour CC env var

[GHC]

#11231: GHC's configure script does not honour CC env var
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        Reporter:  hvr               |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Build System      |              Version:  7.11
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9983             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Herbert Valerio Riedel <hvr@…>):

 In [changeset:"ffc802e8f617d11de9ece7bed438725bde0300b8/ghc"
 ffc802e8/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="ffc802e8f617d11de9ece7bed438725bde0300b8"
 Drop Xcode 4.1 hack and fix ignored CC var issue

 Xcode 4.1 was released back in 2011 for Mac OSX 10.6/10.7.
 However, OSX 10.7 reached EOL sometime around the end of 2014.
 So this `--with-gcc-4.2` hack shouldn't be needed anymore.

 Moreover, this patch changes ./configure to honor the CC env-var
 again (and thus fix #11231) while giving `--with-gcc=...` a higher
 priority over `CC=...`.

 So the following 3 invocations are equivalent now:

   CC=... ./configure
   ./configure CC=...
   ./configure --with-gcc=...

 Since `--with-{gcc,clang}=...` is a misnomer (as is made apparent by
 `--with-gcc=clang` or `--with-clang=gcc`), this would give us a neutral
 and idiomatic way to tell ./configure which C compiler to use.

 Moreover, `./configure --help` says at the end of its output:

   Some influential environment variables:
     CC          C compiler command
     CFLAGS      C compiler flags
     LDFLAGS     linker flags, e.g. -L<lib dir> if you have libraries in a
                 nonstandard directory <lib dir>
     LIBS        libraries to pass to the linker, e.g. -l<library>
     CPPFLAGS    (Objective) C/C++ preprocessor flags, e.g. -I<include dir>
 if
                 you have headers in a nonstandard directory <include dir>
     CPP         C preprocessor

   Use these variables to override the choices made by `configure' or to
 help
   it to find libraries and programs with nonstandard names/locations.

 Consequently, by honoring CC=... (rather than ignoring it) we increase
 consistency and reduce user confusion. Ideally, CC=... would become the
 recommended way to set the C compiler, and `--with-{clang,gcc}=...`
 would be demoted to legacy aliases.

 Reviewed By: erikd, bgamari

 Differential Revision: https://phabricator.haskell.org/D2046
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11231#comment:3>
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