C++ and Systems Fundamentals

This interview assesses your foundational knowledge in C++ programming language features, memory management, concurrency, and low-level systems concepts. Be prepared to discuss the following topics in detail:

1. C++ class vs struct

• What are the differences between class and struct in C++?
• Can a class have a reference (T&) as a data member? What are the implications of doing so?

2. Virtual Constructor

• Can a constructor be virtual in C++? If not, describe patterns or techniques that achieve “polymorphic construction.”

3. Pointer vs Reference

• What are the key differences between pointers and references in C++? Consider aspects such as nullability, reseating, object lifetime management, Application Binary Interface (ABI) implications, and typical usage patterns.

4. Placement New

• Explain what placement new is.
• When would you use it?
• What manual steps are required after using placement new?

5. Performance Comparison (Cache/Memory Effects)

• Compare the likely performance and CPU/memory behavior of the following two code snippets. Assume data points to a large int array of length 64 * 1024 * 1024 allocated on the heap.
  • Code A: Increment data[0] in a tight loop N times.
  • Code B: Increment data[i] for i = 0; i < N; i += 8.
• Discuss relevant concepts including caching, prefetching, write allocation, store buffers, and memory bandwidth to explain why one might be faster than the other.

6. Function Pointer Type

• Given the declaration int (*s[10])(int);, what is the precise type of s?

7. unordered_map vs map

• Compare std::unordered_map and std::map in C++. Discuss their complexity guarantees, ordering properties, iterator invalidation rules, memory overheads, and typical use cases.

8. Overloading vs Overriding

• Explain the concepts of function overloading and method overriding (virtual dispatch) in C++.

9. Mutex vs Condition Variable

• What specific problems does a mutex solve, and what problems does a condition variable solve?
• Why do condition variables require a mutex and a loop around the wait operation?

10. What Causes a Physical Memory Access?

• At a high level, describe the events or conditions that force the CPU to access DRAM (as opposed to a cache hit). Include discussions on page faults, Translation Lookaside Buffer (TLB) misses, cache misses, and Direct Memory Access (DMA).

11. Shared Memory Synchronization

• If multiple processes or threads communicate via shared memory, how do you correctly synchronize access to ensure data consistency and avoid race conditions?
• Discuss various options such as process-shared mutexes, semaphores, futexes, and file locks, along with their potential pitfalls.

12. Linux Networking and Virtualization (High Level)

• Describe how a packet travels through the Linux networking stack.
• Explain how common virtualization primitives (namespaces, veth pairs, bridges, TAP devices, iptables/nftables) fit into that packet's path.