C++: Understanding static vs. global linkage Notice the static keyword in the image? The compiler uses it to make smarter decisions. After parsing, the optimization passes kick in: 1️⃣ Constant Folding Inputs are constants, so the result (10) is calculated at compile time. 2️⃣ Inlining The function calls in main are replaced with the raw result 10. 3️⃣ Dead Code Elimination Look at the top-right pane (-O3): - The static Foo is deleted (unused & internal). - But the global foo is kept! ⚠️ Why? Default linkage is external. The compiler preserves foo for potential linking by other files. Can we fix this? Yes, with the Link Time Optimization (-flto). The linker examines all modules, confirms no one calls foo, and finally removes the dead code.