Why would you want to implement your own allocator?
The goal of these rules is to improve reliability and timeliness of your application. If you intend on working around those rules to do what the rules explicitly forbid then either you or the rules are wrong.
Suppose your problem intrinsically has variable numbers of variable size records coming and going at runtime. Sure you can allocate a big array upfront. But it seems to me that the code which directs records to slots in this array is an allocator.
