The Source-Location Identity Rule

Understanding C++ template instantiation and source-location identity

This is a hard C++ question that tests deep knowledge of how the language resolves template instantiation, identity rules, and the interaction between temporary objects and language semantics. It rewards careful reasoning about what the standard actually guarantees, rather than guessing based on compiler behaviour.

To answer correctly, you need to reason through how C++ handles template parameter deduction when a temporary is passed as an argument, what constitutes object identity in the type system, and how the rules differ between lvalues and rvalues. The question probes whether you can distinguish between what a particular compiler might do and what the standard permits—a critical skill in low-latency code where portability and correctness matter equally.

• Template argument deduction and reference binding rules
• Temporary object lifetime and scope
• The relationship between source location and object identity
• Differences in how lvalue and rvalue references interact with temporaries