>> Of course the question is as you point out, what to do if push_back
comes in above the maximum size?

I have spent years working in environments where the answer was to identify
the person responsible and send them a stack trace. And soak test the
program for weeks at a time to make sure it never happened.

The ideal solution is to require every file to be loaded to be a memory
image that is uncompressed into fixed size predetermined blocks of memory.
Then you can look at the file size on disk and say "yeah that fits."

That is what I expect Grand Theft Auto to be doing. That is the only way to
get 100% RAM utilization with perfect memory safety, minimum disk read head
movement, minimum processor overhead.

However, these days the game consoles are more like PCs so there just isn't
the same need for rigor.