> Instead, what should do is preserve the arguments; the value associated
> with #:configure-flags should be changed to replace any
> --enable-languages=.* flag with yours.  See ‘gcc-boot0’ in base.scm for
> how to do that.

Are you talking about the ‘substitute-keyword-arguments’ part?

> Alternately, you could turn the current ‘gcc-4.8’ definition into a
> ‘make-gcc-4.8’ procedure like this:

>   (define* (make-gcc-4.8 #:key languages)
>     (package
>        ...

>        #:configure-flags ... ,(string-join languages ",")

>        ...))

>   (define gcc-4.8
>     (make-gcc-4.8 #:languages '("c" "c++")))

> That would probably be easier to work with.

I don’t like the above version because it doesn’t allow to choose the
version of GCC.  I’ve attached my version, how can I make it look
better?

Also, ‘/nix/store/nxpzxlvg5z5qq10wzxrzk9hjyhxyicxq-gfortran-4.8.1/bin’
contains these programs:

c++     gcc-ranlib             i686-pc-linux-gnu-gcc-4.8.1
cpp     gcov                   i686-pc-linux-gnu-gcc-ar
g++     gfortran               i686-pc-linux-gnu-gcc-nm
gcc     i686-pc-linux-gnu-c++  i686-pc-linux-gnu-gcc-ranlib
gcc-ar  i686-pc-linux-gnu-g++  i686-pc-linux-gnu-gfortran
gcc-nm  i686-pc-linux-gnu-gcc

Are C++ and C-related programs supposed to be there?