C++ Object Pool Debugging

A 45-minute C++ OA2 task gives a mostly written object-pool class that does not compile; candidates repair syntax/logic bugs and implement `numAllocated()`. Requirements Given a partially implemented C++ object pool, fix compile-time bugs and implement numAllocated(). Visible structure includes: template <typename ObjectT> struct Node { ObjectT object; Node* next; }; struct Batches { Batches* next; Node* nodes; size_t size; }; Node* allocateBatch(size_t batchSize); Node& getNode(); size_t capacity(); size_t numAllocated(); The code contains multiple deliberately simple bugs and is initially not compilable. The final goal is to compute how many nodes from the pool have been allocated. Notes Treat this as code reading plus C++ fundamentals. The likely invariant is that total capacity equals the sum of batch sizes, and unallocated/free nodes are reachable from a free-list. Then numAllocated() can be expressed as capacity - free_count, unless the skeleton already tracks an allocation counter. Common issues to check quickly: missing semicolons after structs, Node vs node capitalization, incorrect template syntax, pointer ownership, Batches vs batches naming, and references returned from functions whose lifetime is invalid. Because the interviewer explicitly states that the code does not compile, spend the first pass making the compiler happy before reasoning about allocation semantics. This is the OA2 of a C++ SWE assessment; the paired OA1 is a set of three LeetCode-style problems under a forced C++ language requirement. Candidates familiar with object-pool / free-list idioms generally clear OA2 quickly. Preparation Review C++ templates, nested structs, pointer syntax, references, and RAII basics. Practice reading object-pool and free-list code: batch allocation, linked free nodes, acquire, release, and capacity accounting. In a timed drill, first list invariants, then compile-fix, then implement the requested function; do not rewrite the whole class.