Can compiler optimization introduce bugs?

Question

Today I had a discussion with a friend of mine and we debated for a couple of hours about \"compiler optimization\".

I defended the point that sometimes

Answer 1

I had a problem with .net 4 yesterday with something that looks like...

double x=0.4;
if(x<0.5) { below5(); } else { above5(); }

And it would call above5(); But if I actually use x somewhere, it would call below5();

double x=0.4;
if(x<0.5) { below5(); } else { System.Console.Write(x); above5(); }

Not the exact same code but similar.