What can be the possible reasons for the object code of an unchanged C++ file to change on recompilation?

Question

It's not really my question. It's a dormant question I found on quora. One answer was that some of the header files might have changed but the author of the questions claims they did not. I would love to hear what people here have to say :)

Answer 1

• Changed header files
• Different compiler
• Different command line options
• Timestamp in object code
• Nondeterministic code generator or optimizer
• Profile-driven optimization with changed profile
• Nondeterminism induced by changes in OS provided services