Expose 'ocamlc -config' parameter 'ox'

[jonludlam]

This is to allow for easy access to whether a compiler is an oxcaml one or not.

I initially exposed this as the parameter 'ocaml-config:oxcaml' but then decided to stick precisely with what the output of ocamlc -config gives. This makes it hard to change the name of that value, so it's worth confirming this constraint is OK with the oxcaml devs.

[rgrinberg]

For reference, do you have the corresponding PR that introduced this change?

[Alizter]

We already have the %{oxcaml_supported} variable. Or is this different?

[jonludlam]

For reference, do you have the corresponding PR that introduced this change?

oxcaml/oxcaml@86911a1

[jonludlam]

We already have the %{oxcaml_supported} variable. Or is this different?

This seems a bit more robust to me than matching the version number to 'jst' or 'ox', and fitted in nicely with the other ocaml-config variables. I think there's a reasonable argument to expose the rest of the values provided by ocamlc -config, many of which seem to me to be a bit like feature flags (e.g. 'parameterised-modules', 'stack-allocation', etc). This could help as these features get upstreamed, maybe?

(I should probably also mention that the oxcaml_supported change predates the change that added the flag to ocamlc -config)

[rgrinberg]

This seems a bit more robust to me than matching the version number to 'jst' or 'ox', and fitted in nicely with the other ocaml-config variables

I agree. Why don't we change the implementation of oxcaml_supported then as well?

I think there's a reasonable argument to expose the rest of the values provided by ocamlc -config, many of which seem to me to be a bit like feature flags (e.g. 'parameterised-modules', 'stack-allocation', etc). This could help as these features get upstreamed, maybe?

That would be welcome as well.

[maiste]

I agree that the goal was to have this to replace the +ox lookup functions. We should update these functions to also check for the ocaml_config. This way we would make oxcaml_supported use it.

[maiste]

My suggestion would be for the test cases to be in the test-cases/oxcaml repository as it is related to it.

[rgrinberg]

@jonludlam do you mind adding a CHANGES entry?