[Openmp-commits] [llvm] [openmp] [OpenMP][OMPT] Error when registering EMI and non-EMI callbacks (PR #213697)

[Jan André Reuter via Openmp-commits]

Thyre wrote:

> Out of curiosity: Is that restriction something that the runtime has to enforce?

That's a good question. With the wording in OpenMP v5.1 / v5.2

>  These callbacks must not be registered at the same time.

and v6.0 / TR15:

> The deprecated target callback must not be registered if a target_emi callback is registered.

I'd understand this as a user not being allowed to register both callbacks at the same time. From my perspective, "must not" is pretty clear in this case. A runtime returning `ompt_set_always` in a case where a user violates this restriction seems incorrect.

A runtime could decide to ignore this restriction, but this opens a wholer can of worms for implementation-defined behavior. For example, does a tool get both callbacks? If so, in which order? Does `target` still set `target_id`, and will the `target_emi` callback receive that `target_id` via `target_data->value`, or its own set `target_data`?
I think this is one reason why this restriction exists in the first place.

I wasn't involved in any of that discussion though. Maybe @jprotze has a better answer.



https://github.com/llvm/llvm-project/pull/213697