C callbacks for GNU readline command completion

[LdBeth]

Thank you for the feedback.

@nojb

This is unsafe: you need to register the result of caml_copy_string as a GC root before calling the OCaml callback. Otherwise if the GC runs before you use that value (inside the callback), the value may be moved in the OCaml heap but the pointer won’t be updated and it will be left dangling.

Does that mean declare the result using CAMLlocal and call CAMLdrop before return?

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After read the caml/memory.h headers I think it is so. Incidentally, I find that the random crashing in the other http server library I’m using could also be caused by not playing nice with OCaml GC in C code.