Fix Issue 17381 - Checked format string is permissive after floating point argument

[berni44]

On my computer there is no failure, but in the Online D Editor it reports failures since 2.074.1, but worked before.

I just added a unittest to find out on which computers this fails.

[berni44]

Strange. Seems to work on all computers here but fails in the online editor...

PS: Works in the online editor too, when main is made pure. On my computer it works still, when pure is removed. Let's see, what the computers here report...

[berni44]

Meanwhile I found out, that the error was triggered by formatting floats not being CTFEable. Which isn't the case any more (at least for float and double), and hence it is correct that the unittest passes on all testers.

[dlang-bot]

Thanks for your pull request and interest in making D better, @berni44! We are looking forward to reviewing it, and you should be hearing from a maintainer soon.
Please verify that your PR follows this checklist:

• My PR is fully covered with tests (you can see the coverage diff by visiting the details link of the codecov check)
• My PR is as minimal as possible (smaller, focused PRs are easier to review than big ones)
• I have provided a detailed rationale explaining my changes
• New or modified functions have Ddoc comments (with Params: and Returns:)

Please see CONTRIBUTING.md for more information.

---

If you have addressed all reviews or aren't sure how to proceed, don't hesitate to ping us with a simple comment.

Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	17381	normal	Checked format string is permissive after floating point argument

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + phobos#7916"

[berni44]

The problem was the special handling of the ctfp-exception in checkFormatException, which elided the check if all arguments were used.

For fixing this, I used a trick: Formatting NaNs doesn't use snprintf, so I allowed them being formatted instead of throwing on all reals. checkFormatException uses Args.init and hence now always works with floats in CTFE.

[PetarKirov]

The online editor only provides already released compiler versions, so any changes done in a pull request won't be visible in the editor, until a new version is released.

That said, as one of the maintainers of @dlang-tour, I am in favor of adding such feature, but it's not a small amount of work.

[berni44]

The online editor only provides already released compiler versions, so any changes done in a pull request won't be visible in the editor, until a new version is released.

You can choose "dmd-nightly", which sounds like it should be compiled once a day from the github sources. But it's 2.091 currently - see bugreport.

And when choosing "all dmd compilers", it stops with 2.094.

[berni44]

Rebased to restart the tests.