NullPointerException stack trace not available without debug agent

I have recently found a bug that causes a NullPointerException. The exception is caught and logged using a standard slf4j statement. Abridged code below: ``` for(Action action : actions.getActions()) { try { context = action.execute(context); } catch (Exception e) { logger.error("...", e); break; } } ``` As you can see, nothing fancy. However, of all the exception logging statements that we have, just this one does not print a stack trace. All it prints is the message (represented as "...") and the name of the exception class (java.lang.NullPointerException). Since the stack trace on an exception is lazy loaded, I thought maybe there is a instruction reordering issue of some sort and decided to call e.getStackTrace() before the log statement. This made no difference. So I decided to restart with the debug agent enabled. However, because I even attached to the process, I noticed that now the stack traces were printing. So clearly the presence of the debug agent caused some additional debug information to become available. I have since then fixed the root cause of the exception. But I would like to learn why the stack trace was unavailable without a debugger. Anyone know? Clarification: this is not a logging issue. Imagine the same try/catch clause, but in the catch, I print the value of: ``` e.getStackTrace().length ``` Without a debugger this prints '0', with a debugger it prints a positive number (9 in this case). More info: this is happening on JDK 1.6.0_13, 64bit, amd64, linux 2.6.9