The mempool max size is determined by evaluating the mempool dynamic memory usage. This cause the behavior to change between various architectures that have different pointer sizes or different internal representations of the standard library structures. This diff adds a test for the mempool dynamic memory usage calculation, as a first step towards faking this calculation to make it architecture independent.
This test is only valid for glibc based 64 bits architectures for now, and skipped for others.
The goal is to move the mempool memory accounting in such a way that the test will pass on any target.