What to do, if debug behaviour differs from normal execution? [closed]

Question

I have a problem with debugging sessions. My program executes very well in a debug session but if I start a normal run, it behaves completely different.
The problem is, that I cannot say, why it acts different.

One possible reason is the slower execution time because you alway have to press F6 or so.
I tried to insert Thread.sleep(1000); but I don't get the instruction causing the different behaviour.

So: What are hints, best practices to get to know why it acts so different in debug sessions?

Answer 1

I tried to check my assumption I did and check them once more.

Excessive logging could be helpful in some situations, but not always. In my case, it didn't help that much.
With logging you can see, where your assumptions are correct and which of them fail.

My personal solution was Java specific. The Java ClassLoader does not load classes completely since JDK 1.5. In a debug session, it has to be loaded completely. So some variables were not initialized well and the output differed from the normal run.
That reason is very hard to find.

Answer 2

Two solutions:

a) Use poor man's debugger (print to the console) or use a logging framework. After the error happens, analyze the output.

b) Write a test case that tries to reproduce the problem. Even if you can't find it that way, this will clean your code and sometimes solve the issue.

Answer 3

You might observe a race-condition that only occurs when there are no debug statements that slow down execution. It could be helpful to start with reviewing your threading model and to watch out for any possible locks.