Comment by dreamcompiler

> Tail-calls are absolutely harder to debug in general than loops.

I like TCO because I often prefer the expressiveness of recursion over loops. When I need to debug, I turn off TCO. (I'm talking about Common Lisp.)

I agree TCO definitely makes the compiled code not look like the source, and this lossage doesn't happen with either regular recursion or with loops. But various other kinds of optimizations also have that problem.

If you're looking at the assembler output you'll see JMPs where there would have been JSRs without the optimization. So knowing that helps a bit. You just lose the automatic history preservation the stack gave you for free.

Time travel debugging might be an answer here but of course that can be much more expensive than simply keeping JSRs in place.