# newlib second-part options config LIBC_NEWLIB_IO_C99FMT bool prompt "Enable IOs on C99 formats" help Enable support for IOs on C99 formats. config LIBC_NEWLIB_IO_LL bool prompt "Enable IOs on long long" help Enable support for IOs on long long integers. config LIBC_NEWLIB_IO_FLOAT bool prompt "Enable IOs on floats and doubles" help Enable support for IOs on floating point values (float and double). config LIBC_NEWLIB_IO_LDBL bool prompt "Enable IOs on long doubles" depends on LIBC_NEWLIB_IO_FLOAT help Enable support for IOs on long doubles. config LIBC_NEWLIB_DISABLE_SUPPLIED_SYSCALLS bool prompt "Disable the syscalls supplied with newlib" help Disable the syscalls that come with newlib. You will have to implement your own _sbrk, _read, _write... If you plan to port newlib to a new platform/board, say Yes.