C++ is a general-purpose programming language that supports various ways of programming such as procedural, object-oriented, and generic. Its immense power and flexibility have kept it relevant across various industries, making it a prevalent choice for complex software systems or where performance and efficiency are critical. Hiring a proficient C++ developer, however, can be a daunting task. The complexity of the language necessitates a critical evaluation of the candidate's knowledge and skills. This article endeavors to arm you with insightful questions to ask a potential C++ developer, which will enable you to select the most suitable candidate for your project.

Firstly, understanding the developer's grasp of the fundamentals of C++ is crucial. You may want to ask about the C++ Standard Template Library (STL). STL is a collection of template classes that provide common programming data structures and functions such as vectors, lists, queues, and stacks. A proficient C++ developer should understand how to use these structures efficiently and how they are implemented under the hood. Moreover, understanding memory management is vital in C++ due to its lack of garbage collection unlike in languages like Java. Hence, ask about smart pointers and how they help prevent memory leaks.

Secondly, evaluate the candidate's understanding of advanced C++ concepts. Ask about the developer's knowledge of Object Oriented Programming (OOP), which is a programming paradigm used to structure a software program into simple, reusable pieces of code blueprints (usually called classes) which are used to create individual instances of objects. Questions could touch on inheritance, encapsulation, and polymorphism. Additionally, ask about their grasp of templates and template metaprogramming. Templates allow functions and classes to operate with generic types, enabling a higher degree of code reuse. Template metaprogramming, on the other hand, is a meta-programming technique in which templates are used by a compiler to generate temporary source code, which is merged by the compiler with the rest of the source code and then compiled.

Thirdly, consider the developer's experience with modern C++ versions. C++ has undergone several revisions with enhancements and improvements. A proficient developer should be familiar with the changes introduced in C++11, C++14, C++17, and the most recent C++20. For instance, ask about the developer's experience with lambda expressions, auto keyword, and concurrency support, which were introduced in C++11.

Additionally, weigh the developer's familiarity with testing and debugging tools. C++ programs can be notoriously challenging to debug due to issues like memory leaks, dangling pointers, and undefined behavior. Hence, a potential C++ developer should be familiar with tools such as GDB, Valgrind, or IDE built-in debuggers. Also, ask about their experience with testing frameworks such as Google Test.

Lastl, consider the developer's experience with build systems and version control. Building and maintaining a C++ codebase can be a complex task. Ask about their knowledge of build systems like Make, CMake, or Bazel. Also, ask about their proficiency in using version control systems such as Git for collaborative work and code history tracking.

Conceptual understanding aside, the developer's problem-solving skills are equally important. You may consider presenting real-world scenarios or challenges faced in past projects. Ask how they would approach such situations and why they would choose that particular path. This will give you insight into their thought process, decision-making, and adaptability.

Remember, the goal is not only to find a developer with the right skills, but also one who fits your project's context, including the team culture, project timelines, and the nature of the project. A thorough understanding of C++ and its nuances, coupled with the ability to apply these concepts to solve real-world problems, is what makes a great C++ developer. This prompts the need for a careful and detailed evaluation process. The questions outlined are designed to guide you through this process and help you find a developer who will drive your project to success.