chengsun

:loop
  set j, 0
  :loopn
    set y, 0
    set i, 0x8000
    :loopy
      set x, 0
      :loopx
        xor x, y
        set [i], [charoff]

chengsun

You need to recompile newlib with --disable-newlib-supplied-syscalls

If you get a hard fault exception when printf'ing a %d number bigger than 10, you have to re-configure and recompile both gcc and newlib with hard floats:
--with-cpu=cortex-m4
--with-float=hard
--with-fpu=fpv4-sp-d16
--with-mode=thumb

One issue is that printf ignores everything after the first newline you enter in it. so printf("a\nb\n") would only print "a\n". Also, setting the buffer mode seems to make it quite buggy.