Hi Jeff, Try supply CROSS_F77_SIZEOF_REAL and CROSS_F77_SIZEOF_DOUBLE_PRECISION. -- Hui Zhou From: Jeff Hammond via discuss <[email protected]> Date: Tuesday, September 7, 2021 at 6:36 AM To: MPICH <[email protected]> Cc: Jeff Hammond <[email protected]> Subject: [mpich-discuss] configure: error: '' is empty I'm trying to cross-compile MPICH for RISC-V with CROSS_F77_TRUE_VALUE=1 CROSS_F77_FALSE_VALUE=0 CROSS_F77_SIZEOF_INTEGER=4 ../configure --host=riscv64-linux-gnu --prefix=/tmp/riscv/mpich CC=riscv64-linux-gnu-gcc-9 CXX=riscv64-linux-gnu-g++-9 FC=riscv64-linux-gnu-gfortran-9 --with-device=ch4:ofi This results in the following error, which I cannot interpret. checking for size of Fortran type integer... 4 checking for size of Fortran type real... 0 checking for size of Fortran type double precision... 0 checking whether integer*1 is supported... yes checking whether integer*2 is supported... yes checking whether integer*4 is supported... yes checking whether integer*8 is supported... yes checking whether integer*16 is supported... yes checking whether real*4 is supported... yes checking whether real*8 is supported... yes checking whether real*16 is supported... yes configure: WARNING: Unable to determine size of a DOUBLE PRECISION type; using 8 checking for C type matching Fortran real... unavailable checking for C type matching Fortran double... unavailable configure: WARNING: Unable to determine size of a DOUBLE PRECISION type; using 8 checking for C type matching Fortran integer... int checking for values of Fortran logicals... True is 1 and False is 0 configure: error: '' is empty Thanks, Jeff -- Jeff Hammond [email protected]<mailto:[email protected]> http://jeffhammond.github.io/