configure: WARNING: unrecognized options

[Paul Smith]

On Tue, 2013-07-09 at 16:31 +0200, Roberto Nunnari wrote:
> // configure gcc
> # mkdir gcc-build && cd gcc-build
> # ../gcc-4.8.1/gcc/configure --prefix=/opt/gcc481 
> --enable-languages=c,fortran --with-gmp=/opt/gmp --with-isl=/opt/isl 
> --with-cloog=/opt/cloog
> ...
> configure: WARNING: unrecognized options: --with-gmp, --with-isl, 
> --with-cloog

Your most immediate problem is that you're running
gcc-4.8.1/gcc/configure when you should be running gcc-4.8.1/configure.
          ^^^
   
The configure script inside the gcc subdirectory ONLY configures the
compiler itself, it doesn't know about all the other extra stuff.
That's why it doesn't recognize those extra configure flags.