CodeQL

• GitHub’s query language for code analysis. It turns a program into a database of facts (every function, call, and expression) that you query to find bugs and security flaws.
• The surface looks object-oriented, with from / where / select, but underneath it evaluates recursive predicates to a fixed point, with stratified negation and aggregates: the very model of these slides.

from Function f
where f.getName() = "main"
select f, "entry point"

• It powers GitHub code scanning: write a query once, run it across millions of repositories to find every variant of a bug.