Hello, I am trying to compile either `gcc-4.9RC` or `gcc-4.8.2` (both give the error) on Debian (6 or 7, it is a cluster). There is `flex 2.5.35` installed and I even compiled my own flex `2.5.39`. I confirmed it generates a `yy.c` output from a simple `.l` file. Also I learned at gcc documentation, that flex shouldn't be necessary when compiling from a release (which the gcc-4.8.2 is). Nevertheless I always get this in some internal `configure` after running `make`: checking for bison... bison -y checking for flex... flex checking lex output file root... configure: error: cannot find output from flex; giving up make[2]: *** [configure-stage1-gmp] Error 1 make[2]: Leaving directory `***/gcc-bin-8' make[1]: *** [stage1-bubble] Error 2 make[1]: Leaving directory `***/gcc-bin-8' make: *** [all] Error 2 It is configured with: ../gcc-4.8.2/configure --enable-languages=c,c++,fortran --prefix=/home/***/gcc-4.8.2 I have no idea what should I try more. Vladimir