How can "Optimization" option for compiler affect testing using TestComplete 9

Question

On Smart Bear site as recommendation for application with debug info to turn off option "Optimization" (prove: http://support.smartbear.com/viewarticle/32714/)

Who can explain how this option works and how can it affect testing under Testcomplete 9?

Answer 1

When optimization is enabled, the relationship between line numbers and compiled code is not so clear. That affects the accuracy of the TD32 debug information that TestComplete uses. To make sure the debug information is as accurate as possible, SmartBear recommends disabling optimization.

Optimization should have no actual effect on the runtime behavior of your program, though. (If it does, then you're either relying on undefined behavior, or you've identified a bug in the optimizer. Assume the former until you can prove the latter.)