[GHC] #8148: ./configure IGNORES --with-gcc=gcc-4.8, can't build head on os x 10.8 with xcode 5 installed

[GHC]

#8148: ./configure  IGNORES --with-gcc=gcc-4.8, can't build head on os x 10.8 with
xcode 5 installed
---------------------------------+----------------------------------
        Reporter:  carter        |            Owner:
            Type:  bug           |           Status:  closed
        Priority:  highest       |        Milestone:  7.8.1
       Component:  Compiler      |          Version:  7.7
      Resolution:  fixed         |         Keywords:  clang
Operating System:  MacOS X       |     Architecture:  x86_64 (amd64)
 Type of failure:  None/Unknown  |       Difficulty:  Unknown
       Test Case:                |       Blocked By:
        Blocking:                |  Related Tickets:
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Comment (by Austin Seipp <austin@…>):

 In [changeset:"cfd8c7ddcdae47fc676d7b16ce8af7b5328a1041/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="cfd8c7ddcdae47fc676d7b16ce8af7b5328a1041"
 Find the target gcc when cross-compiling

 Summary:
 "./configure --target=TARGET" was broken; it would use the host gcc.
 (So you had to explicitly specify "--with-gcc=TARGET-gcc" also,
 as a workaround.)

 This was broken by commit fc4856f9e811d9a23ae9212f43a09ddf5ef12b26
 for #8148. A comment claimed that FP_ARG_WITH_PATH_GNU_PROG_OPTIONAL
 was the same as FP_ARG_WITH_PATH_GNU_PROG except for not raising
 an error when the program isn't found; but that wasn't true --
 the former didn't prepend the target name when cross-compiling.

 We actually need three versions of FP_ARG_WITH_PATH_GNU_PROG since
 the LLVM tools are usually not prefixed with the target name even
 when cross-compiling. So I generalized the logic in a single macro.

 Test Plan:
 Built with "./configure --target=i386-unknown-linux"
 and BuildFlavour=quick, successfully

 Reviewers: ezyang, austin

 Reviewed By: ezyang, austin

 Subscribers: simonmar, ezyang, carter

 Differential Revision: https://phabricator.haskell.org/D204
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8148#comment:24>
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