This is a great example because if it wasn't presented as "spot the UB", I'd expect very few people would raise a concern.

I've written up a demo with your code, running it through several analysers:

https://gist.github.com/technion/1b12c9b4581e915241d9483c5c2...

The tl;dr here is that tis-interpreter is a fantastic new tool, as it correctly complains about this.

Edit: I also note a departure from yester-year, where every linting tool would only manage to complain about unchecked malloc() returns.