Re: [avr-gcc-list] My program runs correctly when compiled with -Os, but not with -O2

[David Brown]

Lin Nan wrote:
> Could anybody give some tips on it?
>  

It's a little difficult without knowing anything more about your code,
but the most common cause for code that fails with higher optimisation
is missing or incorrect use of "volatile".  It's unusual that the change
from -Os to -O2 makes a difference, since there is seldom much
difference in the generated code.

Try to isolate the problem area and look at the generated assembly to
see the differences.

mvh.,

David