Capture __LINE__ and __FILE__ without #define

Macros are indeed your only choice, at least until std::source_location makes it into the standard and fulfills your wish.

Actually the preprocessor is the only choice when you want to work with line numbers and filenames.

For the compiler it's not possible to use line numbers and filenames as arguments for function calls (or storing them in a variable).

In my company we had the exactly same issue with logging. We ended up with an external script scanning the source files and then building proper functions to call.