Expose version number in compiled library about erfa

[eteq]

👍 , although I'm uncertain how best to do this given that the canonical version number is stored in the configure.ac file instead of in the source code... If necessary it could just be another step to add to the "RELEASE" instructions (making sure they are consistent), but I would like to automate it if feasible...

[sergiopasra]

This is not difficult, a few lines of code. The problem is to convince `erfa-fetch' to include the new function in erfa.h

[sergiopasra]

This is just a proof of concept, the name of the function can be different, etc

[mhvk]

That looks good! Just to make sure I understand: with your changes in #42, the only thing that will get overridden in the current release procedures is your addition to erfa.h, correct? One can let erfa-fetch deal with that, but I feel this is a bit odd, since, at least as written, erfa-fetch does not know anything about erfa versions. Another way to correct the version stuff may be to add something to bootstrap.sh that checks whether or not erfa_version already is in erfa.h, and adds it if not. If we go that route, we might as well do the changes of version number in configure.ac and README.rst as well... Or, from bootstrap.sh, call a specific script that does the above.

@eteq - since you usually do the release, what do you think? What would make life easier?

[mhvk]

Thinking about it a bit more, it might be useful as well to expose the sofa version on which the erfa version is based as well.

[sergiopasra]

We would only need to make erfa-fetch add the definitions of our erfa custom functions into erfa.h. The actual code would in erfaversion.c would stay here in the repository

[sergiopasra]

For the SOFA version, we could make erfa-fetch add a macro (in erfam.h, perhaps?) with the SOFA version and then expose it with another function

[mhvk]

@sergiopasra - both sound good; that keeps the version stuff together.

[eteq]

Hmm, is it possible for the sofa version macro to get at the same places the erfa versions do (configure.ac)? Or is it bit possible to get the custom variables not through to config.h?

Just trying to limit the number of places that require manual updates...

As you the need to update erfa.h each time, that did worry me. I always examine the diff so I'd probably notice the removal, but it would be better to have it baked into erfa_fetch. Not sure the best way to do that generally so that we don't have to keep the two in sync... But maybe we just do this one by hand because it'll probably be the only one like this?

[sergiopasra]

@eteq Yes, I can add a macro in configure so that SOFA_VERSION is set there. It has to be updated manually then.

As an alternative to the erfa.h update, we can include all our extra definitions in a new header, say erfaextra.h, and include it in erfa.h. This way we isolate all possible future changes in one file under our control. erfa-fetch would only need to add a #include erfaextra.h after processing all the definitions in sofa.h and before the license text.

[mhvk]

I like the erfaextra.h idea!

[eteq]

I also like erfaextra.h, @sergiopasra - sounds much easier to maintain!

[eteq]

Done in #42 !