Function gmp_mpfr_sys::mpfr::mpfr_get_str

pub unsafe extern fn mpfr_get_str(arg1: *mut c_char,
                                  arg2: *mut mpfr_exp_t,
                                  arg3: c_int,
                                  arg4: size_t,
                                  arg5: mpfr_srcptr,
                                  arg6: mpfr_rnd_t)
                                  -> *mut c_char