M-x debug-on-entry kill-buffer
That opens the standard Emacs debugger whenever kill-buffer is invoked. It doesn't matter that it's a built-in (primitive, not coded in Lisp).
See the Elisp manual, nodes Function Debugging and Using Debugger.
Following from Drew's suggestion in the comments, we can see that company.el is using condition-case-unless-debug in a number of places, including in company-call-backend-raw -- which in your stack trace is being called after that "WRAPPED IN A CONDITION-CASE" company-call-backend call.
(condition-case-unless-debug VAR BODYFORM &rest HANDLERS)
s is bound to a new function that was recently added, and indeed it appears to be non–functional. I took a look at the source code, and it does attempt to pull file and line number from the stack frame, but none of the stack frames have any file and line number information :)
It then tries to run hook functions, but the list of hook functions is empty. Those ...