Clang Sanitizers (Armin Hasitzka)
Author: Armin Hasitzka
When I joined the Mono voyage in June, I had my mind set on evaluating Clang’s ThreadSanitizer (“TSan”) and, optionally, Clang’s AddressSanitizer (“ASan”) – and what thrilling undertakings they were!
Most of my adventures can be tracked via pull requests as well as on the website. Therefore, as there is a lot of material out there already, I will only list the major cornerstones. The observant and interested reader can find a great amount of links that will lead them to a world full of fascinating stories.
My Journey
Main Quests “Playing with TSan and ASan”:
- Find out how to work with TSan and ASan in combination with Mono
- Add a CI lane for TSan
Main Quests “Permanently Blacklisting Races”:
Side Quests “Dealing with Data Races”:
- Racing with
next_generic_inst_id - Interlock and unlock, part I – Spread unlocked
- Interlock and unlock, part II – Making peace with the past
- Interlock and unlock, part III – Performance counters
- Interlock and unlock, part IV – MonoJitStats
Side Quests “Fixing Thread Leaks”:
Side Quests “Fixing Address Violations”:
Side Quests “Improving Mono”:
Bottom Line
What I Learned
Like many GSoC students before me, I learned how to work properly with git and GitHub. Even though I used git before joining Mono, I never went further than checkout, commit and merge. Working with GitHub and pull requests introduced me to rebase -i, which opened up a colourful new universe full of unexpected possibilities.
Apart from git(Hub), I also learned that obviously, I have a thing for fixing and validating code. When I joined in June, I already liked the idea of static analysers that help me find and fix hidden issues in my code. However, working with TSan this summer raised my interest in these things up to a point at which I can undoubtedly proclaim my passion for code validation. I will focus on (automated) validation of code during the rest of my studies.
What Comes Next
When talking about introducing TSan to Mono, I want to stress that my work should be seen as one first step of many more to come. After taming about 200 races, there is still a large amount of wild races out there. Until the majority of these wild races are taken care of, meaningful investigations with TSan will be difficult.
What makes the matter even more complicated is the fact that TSan, Mono and make lock up at the moment, which might be connected to signal handling. A bug report is filed and will eventually bring light into this dark corner.
Lastly, I would like to introduce the enhancitizer. This tool is the result of my ongoing analysis of Mono with Clang’s sanitizers and helps with automated processing of Clang’s reports. It is still under construction; however, one can get an idea of it by browsing through the snapshot of the output that resulted from analysing 9a634c1.
Thank You
All that is left to say is thank you for this amazing summer! We will surely meet again, completing more quests shoulder to shoulder, and I cannot wait!