How to add a breakpoint into vim

I’m wonder what the absolute most basic way to add a breakpoint into vim is. The equivalent of just ‘passing through’ the breakthrough line number to gdb, for example:

gdb a.out --ex 'b 9'

I’m hoping there is something as simple as an annotation (similar to the >>> for folding code). All the plugins I have come across seem to create an entire debugging environment inside vim which isn’t really what I’m looking for. I’m basically just looking to be able to tag a line as a breakpoint and then to run gdb with those breakpoints automatically added. How can this be done?