When writing safety critical software for limited embedded hardware we had a policy that new features were strictly not allowed to use up the final x kilobytes

When writing safety critical software for limited embedded hardware we had a policy that new features were strictly not allowed to use up the final x kilobytes of the memory, these were reserved for critical safety patches. You don't want to hardware recall millions of units because memory is too low for a software update. This was handled by a build step though, not someone secretly hiding allocation in the actual code.