Converting recursive function to tail recursive

Please delete this thread, I have found the solution. Sorry for the inconvenience

It already looks like it is capable of tail recursion elimination.

Indeed, gcc seems to think so.

Code:

---

$ gcc -S bar.c
$ grep helper bar.s
.globl count_helper
        .type        count_helper, @function
count_helper:
        call        count_helper
        .size        count_helper, .-count_helper
$ gcc -S -O2 bar.c
$ grep helper bar.s
.globl count_helper
        .type        count_helper, @function
count_helper:
        .size        count_helper, .-count_helper

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Closer inspection of the optimised code shows that a jump is used where there should be a call.