AW: [avr-gcc-list] gcc bug

[Andreas Trenkwalder]

Hi!

> struct smotor { uint16_t count; } motor;
> 
> main() {
>       // code to set up a timer which sets up a 
>       // signal handler for SIG_OVERFLOW0.
>       ... 
>       func();
>       // never returns from func().
> }
> 
> func() {
>       motor.count = 10;
>       while(motor.count > 0) {
>               ;
>       }
> }
> 
> signal(SIG_OVERFLOW0) {
>       if (motor.count) {
>               motor.count--;
>       }
> }
> 
> 

Declare the variable motor as 'volatile'!

This indicates that a variable may be changed in a way which is
unpredictable by analysing the normal program flow (such as variable which
may be changed by an interrupt handler). This behavior is also explained in
the AVR-libc FAQ [1].

Regards,
Andreas
 

[1] http://www.nongnu.org/avr-libc/user-manual/FAQ.html