How do you identify and eliminate dead code in your codebase?

Firstly, dead code can clutter the codebase, taking up unnecessary space and resources. This can impact the performance of the application and make it harder to navigate and work with the code. Additionally, dead code can obscure the logic and purpose of the code, making it more challenging for developers to understand and modify the application over time. Moreover, dead code may contain bugs, outdated dependencies, or security vulnerabilities that go undetected. By leaving unused code segments in the codebase, developers risk introducing errors or security vulnerabilities into the application without even being aware of it. Removing dead code is essential to ensure that the application remains secure and free from potential issues.

Identifying and eliminating dead code involves: 1. Static Analysis Tools: Use tools like SonarQube to detect unused code. 2. Code Coverage: Run tests and check coverage reports for unexecuted code. 3. Refactoring Sessions: Regularly schedule refactoring to clean up the codebase. 4. Peer Reviews: Leverage code reviews to spot and remove dead code. 5. Feature Flags: Manage feature flags to avoid leaving obsolete code. 6. Documentation: Keep documentation updated to reflect code changes. 7. Automated Tests: Ensure tests exist for all active code paths.

Be careful on concluding whether code is ‘dead code’ based on dynamic analysis tools. Execution flow is determined by input (data) and/or timing. Different input or a different timing can cause a different execution flow throughout the code. So, when drawing conclusions on ‘dead code’, to be removed, based on dynamic analysis, one should be sure sufficient execution flows are executed. E.g., it might be that a certain piece of code will require a very specific input to be executed (e.g., in an error situation), if this specific input is not provided during the dynamic analysis, this piece of code will be identified as ‘dead code’.

Static Application Security Testing tools that use abstract execution are good at finding dead code. The principle here is that the tool tries to calculate through all paths through the source code, taking the values of variables into account. This provides more comprehensive information compared to dynamic analysis only. Static tools can also explain why they conclude that a piece of code is never hit, helping the developer reason about the code. Now, most tools do not provide guarantees, but they provide a great help in understanding areas of code that could be dead.

Automated tests are effective in verifying code functionality, but their coverage must be comprehensive to ensure all scenarios are tested. It's crucial to consider edge cases and specific situations to guarantee thorough test coverage and validate code behavior accurately.

Static analysis tools are a great help with the code review process. They are easy to use and help provide a more thorough perspective compared to human reviewers. Especially tools that use abstract execution. They go beyond just coding standards and provide a review of additional code paths. From experience, we see that developers are especially struggling with error paths. This leads to memory leaks, uninitialized variables and a whole set of other possible problems. Static analysis can find these early, during the review process and speeds up the testing process.