How can I verify whether a function is expanded as inline by the C++ compiler?

Question

How can I verify whether a function is expanded inline in a C++ program? My Compiler is Emscripten but an answer for g++ probably works.

Ideally, a code that runs differently when in inline mode (although it should not have any side effects).

Answer 1

You can enable the -Winline warning which prints a warning when a function marked inline wasn't inlined.

See the documentation.

As an alternative, you can mark the function always_inline which will trigger an error if it wasn't inlined. See the documentation.