Units that have not been opened

[Beliavsky]

Fortitude is silent about

implicit none
write (10, *) "hello"
end

and some compilers will execute this code by writing to a file fort.10, but the standard does not mandate this, and I suggest that fortitude warn about writing to units that have not been explicitly connected to files.

[ZedThree]

I think this is a really good idea in principle, but I suspect actually tricky to pull off. It's entirely possible that the unit might have been opened in a completely different translation unit. Even just opening it in a different procedure (which I do see in practice) would mean needing to reason about the execution order of those procedures -- even worse if there are any conditionals or control flow involved.

This almost certainly requires more in-depth static analysis than we're currently set up to do, but if we had that, we'd be able to do some very interesting checks.

[Beliavsky]

I see your point. Maybe have an option to warn that unit 10 may not have been opened in the current program unit, and let the programmer decide if there is a bug or reliance on non-standard behavior.