[Bug bootstrap/12745] New: config.if fails when building a "crossback" compiler.

["falemagn at studenti dot unina dot it" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12745

           Summary: config.if fails when building a "crossback" compiler.
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: bootstrap
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: falemagn at studenti dot unina dot it
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-­gn
  GCC host triplet: i386-pc-aros
GCC target triplet: i686-pc-linux-­gnu

In an attempt to port gcc to the AROS platform, and having the source tree
already build a crosscompiler for the i386-pc-aros target, I tried to build a
crosscompiler from i386-pc-aros to i686-pc-linux-gnu, so to test the host
support for AROS.

However, by the time the config.if file is included in configure, the CC
variable is set to i386-pc-aros, and since the the build system is the same as
the target system, these particular lines are executed in config.if:

    if [ ${target_alias} = ${build_alias} ]
    then
      [...]
(*)   ${CC-cc} $dummy.c -o $dummy 2>/dev/null
      [...]
    fi

As said, since CC is set to i386-pc-aros, and since AROS knows nothing about
glibc, the compilation fails and config.if bails out with "Cannot find the GNU C
library minor version number.". 

I don't know whether CC should really be set to i386-pc-aros there, however if
the (*) line is substituted with 

(**)  ${CC_FOR_BUILD-cc} $dummy.c -o $dummy 2>/dev/null

Then config.if works as it should: after all, why use the host compiler if we
are interested in the _build_ one?