Thank you very much to you all,
I'll recompile with "--enable-largefile" and try it, and eventually dive in r.terraflow Makefiles.
Michele.
So 10050 x 7760 cells * 80 bytes * 2 = ~12gb disk space needed, and as
David mentions this is bigger than 2GB so you will need to have GRASS
built with large file support*. If you did build GRASS with large file
support, then this is a bug as the r.terraflow Makefiles aren't checking
for that flag and making the needed adjustments. I'm pretty sure that
this has not been fixed but don't know enough about LFS and the
inner workings of the configure system to fix it myself.[*] ./configure --with-cxx --enable-largefile
Hamish