rem: for(i=0; i < len; i++)
add: for (i = 0; (size_t)i < len; i++)
context: do_read_test(int argc, char **argv){    int    i, err;    char   *buff;    size_t len = 256;            if (cur_fd < 0) {        printf("no file open! (open or create one with open or make)\n");        return;    }    if (argv[1] && isdigit(argv[1][0]))        len = strtoul(&argv[1][0], NULL, 0);    buff = malloc(len);    if (buff == NULL) {        printf("no memory for write buffer of %d bytes\n", len);        return;    }    for(i=0; i < len; i++)        buff[i] = (char)0xff;    err = sys_read(1, cur_fd, buff, len);        if (len < 512)        hexdump(buff, len);    else        hexdump(buff, 512);    free(buff);    printf("read read %d bytes and returned %d\n", len, err);}