when does the compiler necessarily not make a function marked inline as inline

Question

When does the compiler necessarily not make a function marked inline as inline?

Answer 1

Most obviously it can't inline the function when you take a pointer to the function. If you pass around the pointer and (maybe later) decide to call the function through the pointer, the compiler has to generate a non-inlined version of the function. Of course if the function is called directly, the compiler might still inline it. And the compiler is also free to not inline the function anyways.