code to generate error messages

macro_problem_1220.c (text/plain), 1.74 KB, created by David Relson on 2011-12-23 01:07:11 UTC

// command:	msp430-gcc -c -o macro_problem_1220.o macro_problem_1220
//
// gives:	macro_problem_1220:24:5: error: invalid use of void expression
// gives:	macro_problem_1220:41:5: error: void value not ignored as it ought to be

#include <msp430g2231.h>

// following are #defines and prototypes involved in the error message
// msp430g2231.h:106:#define LPM0_bits (CPUOFF)
// msp430g2231.h:114:#define LPM0      _BIS_SR(LPM0_bits)     /* Enter Low Power Mode 0 */
// msp430g2231.h:121:#define LPM3_EXIT _BIC_SR_IRQ(LPM3_bits) /* Exit Low Power Mode 3 */

// intrinsics.h:140:#define _BIC_SR(_b) __bic_status_register(_b)
// intrinsics.h:142:#define _BIC_SR_IRQ(_b) __bic_status_register_on_exit(_b)
// intrinsics.h:142:#define __bis_SR_register(_b) __bis_status_register(_b)
// intrinsics.h:96:void __bis_status_register_on_exit (unsigned int bits);
// end of #defines and prototypes

// ***************************************************
// macro_problem_1220:24:5: error: invalid use of void expression

void Low_Power_Mode__Port_1(void)
{
    _BIC_SR(LPM3_EXIT);
}

// analysis:
//
// LPM3_EXIT expands to a call to a void function, i.e. __bic_status_register_on_exit()
// this call is used as the parameter to _BIC_SR, i.e. to __bic_status_register
//
// question:
//
// is the return type of __bic_status_register incorrect?

// ***************************************************
// macro_problem_1220:41:5: error: void value not ignored as it ought to be

void Timer_Blink_LED__main(void)
{
    __bis_SR_register(LPM0 + GIE); // LPM0 with interrupts enabled
}

// analysis:
//
// LPM0 expands to a call to a void function, i.e. __bic_status_register()
// GIE is added to the result of this call
//
// question:
//
// is the return type of __bic_status_register incorrect?