Avoid atomic 64-bit load on Debian armel

[glondu]

Bug: #13234

[gasche]

This looks fairly nice to me (having a configure check for the feature itself is a nice touch). @dustanddreams, do you agree with this approach?

[gasche]

I approve of this change, but I would wait for @dustanddreams' opinion before merging.

[gasche]

This changes required a substantial amount of work, so I think it would deserve a Changes entry. If I had to write one myself, I would suggest something like this:

- #13234, #13267: fix a compatibility issue with Debian armel (armv5) systems
  (Stéphane Glondu, review by Miod Vallat and Vincent Laviron)

(I chose to attribute the substantial debug and guessing work done by other people as "review", and did not mention my own review which is rather trivial in comparison.)

[gasche]

You should regenerate it yourself and can include this in the patch. (As you run "git push", you can raise your hand and declare to yourself (but out loud) that you are not xz-ing us.)

[glondu]

You should regenerate it yourself and can include this in the patch.

Done.

(As you run "git push", you can raise your hand and declare to yourself (but out loud) that you are not xz-ing us.)

If so, that wouldn't be deliberate. I've been maintaining OCaml in Debian for more than 15 years and I am attached to my reputation :-)

[ghost]

I agree with #13234 (comment) that this should better be a compile-time choice. (__ARM_ARCH <= 5 or something similar)

[glondu]

OK, I removed the configure-time detection.

[gasche]

I'm happy as well with the new implementation (it is worse in some aspects (it won't automatically work for other systems that would have the same restriction) and better in others (it works better for mild cross-compilation scenarios).) Thanks @dustanddreams for your feedback!

[gasche]

Thanks! I cherry-picked in trunk as a37ec68.