Simon,
I see where you are coming from. So let me try to outline how I usually handle this: this silent change (even with deprecation) likely alters one
of the build products, and hopefully(!) someone will get suspicious (because the build products are used (otherwise why bother building them
in the first place). Thus someone flags that something with hpc is off. At which point I'd go and manually investigate what is going on, at _that_
point, I will see this, either because I'm reading the logs, or because the compiler reports it to me while manually running it.
1. I upgrade the compiler.
2. I observe a change.
3. I try to figure out where the change comes from.
If in (3) or maybe (2), I am told pretty directly what the change is, it's much easier for me to adjust. Even better if the change message includes
instructions on how to adjust. Even better if someone else can observe the change, _and_ know as well as having been given actionable advice
on how to proceed. If I can cut myself out of the whole "Something broke, I looked at it, but can't figure out what's going on, and got way too much
on my hands, please someone else dig into it" situation, it's a win. Not only for the person experiencing the change (they don't feel helpless, nor do they
need to ask for assistance), but also for the people supporting these kinds of issues as they don't come up in the first place.
The difference is between it taking 10min to figure, and providing the agency to understand and solve it alone, or needing to reach for support it
taking 60+min to figure out and correct, because one has to dig into all the changes and details. Maybe LLM will cut this a bit because one could
ask "I'm seeing some strange behaviour regarding -fhpc, please provide a summary of the relevant changes between X and Y".
I like SPJ's suggestion in this thread quite a bit and will ask the Author about their opinion.
In general we seem to be in agreement around the current default not being ideal, and somewhat hung on the deprecation notice part. With an
eye on our stability goals, I'd like to see us try light deprecation warnings. I see that Adams' solution is much more thorough, I also agree that it's
a lot more involved.
If anyone has qualms around accepting this with a light deprecation notice, please speak up, otherwise I'll mark this proposal as accepted, and
merge it in a few days after David responded.
Cheers,
Moritz