Posted on May 17, 2011 at 12:44> I was thinking that if everything was volatile, the compiler would not assume anything was zero, even if it thought it had been initalised to zero.
the compiler won't assume any globals are zero unless they are const; volatile doesn't enter into it. in theory a global optimizer could find such things out. in practice compilers work with compilation units and a compiled unit must operate correctly when linked with all possible future compiled units, which means the compiler can't make assumptions now about what yet non-existing units will store or not and where. so globals won't be assumed to have any particular value.
that said, if the compiler did assume a zero, it'd be good for you. if a global should be zero but is not, code that depends on that fact will malfunction; unless the code just assumes the value is zero and doesn't read it, in which case it'll work fine!
(note that global statics are only visible within their compilation unit and current compilers could global-optimize on them. no idea what actual compiler do.)
