[En-Nut-Discussion] ICC AVR 7.13A Compiler Bug

[Jean Pierre GAUTHIER]

Hello,

With the ATMEGA2561, nut/dev/usart.c seems to be bad compiled with ICCAVR
(version 7.13A). (tested with NUTOS 4.2.1 and 4.3.99)

At the end of the UsartRead(NUTFILE * fp, void *buffer, int size) function, 
for exemple, when 1 char must be read (size=1), rbf->rbf_cnt is decremented
by 128 instead 1!
To avoid this, insert dummy instruction(s) as below. 
Of course other instructions, upon your imagination, should be inserted ;-) 

Best regards,
Jean Pierre

End of Nut/dev/usart.c/UsartRead()function :

    /*
     * Get raw characters from receive buffer.
     */
    else {
        if ((rc = size) > avail)
            rc = avail;
        for (taken = 0; taken < rc; taken++) {
            *cp++ = *rbf->rbf_tail++;
            if (rbf->rbf_tail == rbf->rbf_last) {
                rbf->rbf_tail = rbf->rbf_start;
            }
        }
    }

    if (taken) {
        taken++; // <----------- insert dummy instruction
	  taken--; // <----------- insert dummy instruction
        NutEnterCritical();
         rbf->rbf_cnt -= taken ; // a compiler bug was here!!!
        NutExitCritical();
        if (rbf->rbf_cnt < rbf->rbf_lwm) {
            (*dcb->dcb_rx_start) ();
        }
    }
    return (int) rc;
}