> int c ;
> int test( int p){
> int i;
> i = p;
> return (i+2+c+2+c+2+c);
> }
> int main(){
> c = test(128);
> }
Hmm....yes, from C perspective, there's nothing can modify c before it's
used the first time (unless you inject the startup code). Therefore, the
compiler is safe to assume that c is its initial global value (0) and is
able to use constant propagation, with c assumed as constant to reduce the
function call into a simple value.
The case with Pascal is not the same, however. Pascal has unit system with
initialization section that can inject code before the main block is
executed. A unit can extern-ize the variable and modify it in its
initialization section. So it's not safe to assume the same thing as C does
above. It's not impossible, but would be harder to implement, probably
requiring whole program analysis.
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