Dear mpich staff， when I'm installing mpich-3.3.1 using gcc-8.3.1, unset F90 export F90=gfortran export F77=gfortran ./configure --prefix=/home/majun2/dat01/setup_new/mpich/ error shows: nfigure: WARNING: installation or configuration problem: Fortran 90 compiler cannot create executables. checking whether Fortran 90 compiler works with Fortran 77 compiler... configure: WARNING: See config.log for the failed test program and its output. no configure: error: The selected Fortran 90 compiler gfortran does not work with the selected Fortran 77 compiler gfortran. Use the environment variables FC and F77 respectively to select compatible Fortran compilers. The check here tests to see if a main program compiled with the Fortran 90 compiler can link with a subroutine compiled with the Fortran 77 compiler. config.log is attached below, anybody know what's the problem? thanks a lot!