What do you do if you cannot resolve a bug? [closed]

Answer 1

I usually ask someone else to take a look at the code. While I'm explaining what the code is supposed to do, I sometimes see the bug just as I talk.

When a bug is a tough one, I sit and work until I figure it out and solve the problem. Interestingly enough, there are times when catching a mysterious bug is more enjoyable than everything running smoothly. And the relief and feeling when a bug is resolved, well, not many other things can beat that (except the obvious ones).

Answer 2

There are a lot of good tips here.

One that I absolutely do not agree with is the concept of changing the code hoping that it will go away. First off, you a probably going to introduce new bugs. Seconds, you can easily change things enough to hide the bug only to have it resurface again with the next patch.

Memory corruption bugs are especially likely to vanish as magically as they turn up. However, the memory corruption bug isn't fix, it is only that non-fatal areas of memory are getting trashed.

1) Try a different debugger. For example, I use WinDbg more and more often. When you load a program in a debugger, memory layout for your application will change slightly. Maybe a different debugger cause the error to manifest slightly differently.

2) If you resort to changing code without knowing exactly what the problem is, then if the bug goes away, YOU MUST go back and understand why the change fixed the bug. Otherwise, you are probably just hiding the bug.

3) Talk to others about the bug, maybe they have seen different versions of the same problem (i.e. other ways to recreate it)

4) Logging.

Answer 3

I honestly cannot recall a bug that I couldn't fix. It may cause a lot of refactoring, or may take a while, but I've never had one that I can't get rid of. If it takes me more than an hour to track it down then it's almost always something really stupid and small like looking right past that : that should've been a ;, etc.

In python, if I'm using an editor that isn't mine, or maybe it's someone else's code, I use retab! in vim, or paste into something like pastie to check indentation (if I don't have vim available).

If it's not a crasher/deal breaker, then I move on and come back with a fresh pair of eyes.

Oh, and you can never, ever have too much logging.

Answer 4

I do a number of different things:

• throw out all my assumptions and start from scratch. Remember, a bug exists because something which appears correct is actually wrong. Even those lines or functions or classes that you are absolutely certain are correct may be incorrect. Until you can convince yourself of the correctness you can't assume anything is right.

• keep putting in print statements and assert statements to eliminate things and allow me to reform new assumptions.

• step through code in the debugger if the problem is a control flow problem. Don't step over functions. Step in them and go through all the detail of their execution to confirm they are working right. Confirm the arguments and return values.

• If a line or function or class is suspect but I can't prove it in situ, then write a small test case that does what you think the problem construct does. This may locate the problem or give some insights as to where to look next.

• stop for the day. It's amazing what kind of offline processing your brain will do overnight. Often the answer or a key insight will appear the next day while I'm doing something mindless like showering or driving.

Answer 5

use more creative methods of tracking the bug down.

using remote debugging on the machine where its reproducable.

using profiling tools.

introduce more logging to the app.

Answer 6

I get a bit demoralized too when unable to solve a bug. Usually when I hit a wall with a bug, I would just take note on my findings and stop working on it. I would jump on another bug that is easier to solve and then came back to the bug. By doing this, I would have a fresh mind and attitude in tackling the bug. Sometimes you might have tendency to overcomplicate things when spending too much times on a bug. Having a break, helps in breaking the wall.

RWendi