by Leon Rosenshein

Hello. Who Are You?

There are lots of times in logging and observability that you write a nice standard function to handle the boilerplate part(s), making it easier to focus on what you want to say/observe. And that's a good thing. Being able to focus on what you want to say and not worry about the details of getting the message out reduces cognitive load and increases the likelihood that things will be said.

And one thing you often want to know with logging/observability is which function is making the call. You might be using structured logging and want to fill out the Function member, or you might want to set a tag on your metric. The easiest way to do that is add a string variable to function's parameters and pass it in. That's a good min bar.

But there are problems with that. If you have multiple calls in a function you need to spell it the same every time. Do some refactoring and it's wrong. Rename the method and it's wrong. A little bit of copy-pasta and it's wrong.

You can avoid that by good use of constants and local variables, but it's still error-prone and there's no way to catch it automatically. There is however a better way, and it's not subject to those limitations. Let the compiler do it for you.

You're probably familiar with the predefined C macros __FILE__ and __LINE__, but since C++ there's also __func__. That's a good place to start in C/C++. Different languages have different specifics, but there are also (almost) always ways to access this info as well as the current call stack, so if you really need the function name, getting it automatically is often a better approach.

One thing to keep in mind is that while the compile time methods are fast, any of the runtime methods may incur significant time penalties, so make sure your not blowing your time budget :)