Meeting C++ 2025 - Case Study: Purging Undefined Behavior and Intel Assumptions in a Legacy Codebase

Roth Michaels

On Day 1 at 16:00 (CET/Berlin) in Track E [Amethyst Room and online]

For large C++ codebases, adding support for a new platform (e.g. Apple Silicon/ARM) can be a scary, expensive endeavor.  One of the biggest causes for alarm is undefined behavior (UB), which is an unfortunate part of many legacy codebases; luckily there are tools to help.  After a brief review of what undefined behavior (UB) is we will discuss what issues it can cause and why it should be avoided. We will look at a few real-life bugs caused by UB in our codebase and discuss a common type of UB in legacy codebases: "it works on Intel".  We’ll discuss how eliminating undefined behavior from a cross platform codebase can reduce maintenance costs and make it less stressful to support new platforms for your codebase.  Then, we’ll go over the specific cultural and tooling initiatives we used to eliminate undefined behavior in our C++ codebase, including how we used static analysis and clang sanitizers to identify and address issues.

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