A 1-line macro is not bad. stb's stretchy_buffer is not bad, but it could do with less macros. Take the ones from my own example that I linked elsewhere on this page.

If you use macros "correctly" there is rarely any logic in there, and they are decidedly not hard to debug. Macros let you do things that you could not do otherwise, like getting information about the caller or the size of the element type that is abstracted behind a void ptr.

C++ templates on the other hand - if you have considerable C++ experience you will shy them. They drive compile times up insanely, and are actually very difficult to debug, at least under "normal" usage.

Also, code bloat results after a few instanciations where a simple runtime integer could be used to discriminate between different cases, but with shared implementation code.

I would never again touch even the most basic C++ template, that is std::vector. I prefer my simple 3 lines of macros.