Excuse me for butting in, but I don't understand what makes anyone think this code _ought_ to produce the same results at different -O levels[*]. The C language spec is explicit that this is undefined behaviour.
As every software that do data-processing you need it will reproduce the same behavior with any not-altering-semantic-option.
Well if you put garbage in you will obtain garbage out, but the problem can raise if the garbage generation is not deterministic.
If the code is syntattical garbage ===> compiler don't compile it
if the code is semantical garbage ===> same compiler must generate the same output (in .s or in .o) ==> you must obtain the same result.
or not?
Luca Benini
