Do You Know How to Debug Code?

A Portuguese version is available here

Debugging, or troubleshooting, means thoroughly examining code to detect and eliminate potential errors. Debugging is already an exhausting process and a real challenge in itself. As we advance in our careers, we need to debug not only our code but also our colleagues' code. If that weren't enough, we also face challenges like performance debugging, security, race conditions, and other complex debugging tasks.

Recently, I went through a situation that made me reflect on debugging. I was informed that an implementation I had just delivered was not working as expected. The task involved sending data from a specific record, including the creation date, to an external service. I implemented it, wrote functional tests, performed local tests, and "confirmed" that everything was working correctly. However, BANG!, it wasn't. During debugging, I discovered that a method I frequently used did not return the record's creation date when called remotely. This method, which worked in one context, exhibited different behavior during remote execution.

This episode illustrates the importance of questioning our assumptions. When confronted with a bug, it is crucial to recognize that we might be wrong about one or more of our assumptions. We should not ignore a block of code involved in the bug just because we "know" it works. We must test. Test again. And again with different data and conditions, exploring all possible scenarios.

Stay calm. Panicking is a common reaction when an unexpected problem arises. However, it is essential to face the situation calmly and clearly. Tension can cloud your judgment and make it harder to identify the true source of the problem. We must take a deep breath, analyze the situation objectively, and avoid rash decisions that could worsen the situation.

Accept that the problem exists and focus on solving it. Denying the existence of the problem or downplaying it will not make it go away. Keep an open mind to different possibilities, but avoid tunnel vision. We must identify and address the root cause of the problem, not just the side effects.

Act on the root cause. When confronted with a bug, the tendency might be to try to resolve the issue directly where it manifests. However, this approach may not only be ineffective but could also further harm the code.

Here are some helpful tips for effective debugging:

• Don't make assumptions. Assuming that part of the code is working correctly without testing it can lead to errors. Check each part of the code involved in the bug.

• Reproduce the bug. Consider the inputs and outputs. Try to replicate the problem exactly as it occurs.

• Visualize the state of your data. Understand how the data is being manipulated and how it should be at different points in the process.

• Trace the data. From visualizing the data, start tracing how it flows through the system. This can help identify where the data is deviating from the expected.

• Start somewhere. When unsure where to start, use binary search as a strategy. Split the problem into two parts. If the problem is present in the first half, the bug is between the start and the midpoint; otherwise, it is between the midpoint and the end.

• Eliminate logically. The operating system is not malfunctioning. The database engine is processing your query correctly. Remember the saying: If you find hoof prints, think of horses—not zebras.

Conclusion

Debugging is a vital skill for any programmer, requiring not only specific techniques but also the right mindset. Staying calm, accepting the existence of the problem, and starting the analysis from the beginning are fundamental steps for successful debugging. Every bug is an opportunity to learn and improve your skills, both in problem-solving and maintaining mental clarity in the face of challenges.