Block Pool Resource

Implementing a fixed-size block pool allocator in C++

This hard C++ coding problem tests your ability to build a custom memory resource that chains allocation strategies. It is representative of the kinds of questions asked in performance-critical environments — high-frequency trading, game engines, and systems programming — where pre-allocated, fixed-size pools eliminate the latency and fragmentation of general-purpose allocation.

The core challenge is to implement the std::pmr::memory_resource interface correctly: managing a contiguous buffer as a free list of uniform blocks, delegating oversized or unavailable requests upstream, and tracking which allocations belong to the pool versus which belong to the upstream resource. Strong solutions pay careful attention to pointer arithmetic, alignment constraints, and the invariants that must hold before and after each operation.

• Free-list data structures and intrusive linking
• Inheritance from abstract base classes and virtual method dispatch
• Memory alignment and address-range checking
• Resource delegation patterns and ownership boundaries