SFINAE

Understanding SFINAE in C++ template specialization

This is an easy language-knowledge question that tests your grasp of Substitution Failure Is Not An Error (SFINAE), a core C++ template metaprogramming principle. It asks you to trace through template instantiation and determine whether a given code snippet will compile on a 64-bit system.

To answer questions like this, you need to understand how the compiler attempts to substitute template arguments into function or class definitions, and what happens when that substitution fails. SFINAE allows the compiler to discard a candidate template specialization without raising a hard error, enabling overload resolution to fall back to other viable candidates. Interviewers use SFINAE questions to verify you can reason about template resolution order and compiler behavior at a detailed level.

• Template substitution and candidate generation
• Implicit type conversions and their role in overload resolution
• The difference between substitution failure and instantiation error