What was the most stupid bug you could not find for a long time? [closed]

Question

I was working on a project that missbehaved, for some reasons no exception was thrown even when it should have. Deep down I have found this kind of error handling:

try {
    m.invoke(parentObject, paramObj);
} catch (IllegalArgumentException e) {
    new CaseLibException(e);
} catch (IllegalAccessException e) {
    new CaseLibException(e);
} catch (InvocationTargetException e) {
    new CaseLibException(e);
}

My brain recognized that several exceptions were wrapped into another one, so that's not so bad. But I had to stumble over this code at least 3 times to see what's missing...

What is your most stupid bug you could not find?

Answer 1

I fixed a bug once where the application crashed every day at 6:12pm.

Turned out that someone had stored the number of seconds since the start of the day in a 16bit int.

Answer 2

In C/C++ (which I learned recently)

if (x = 0) {
...
}