RFR: 8290373: Enable lossy conversion warnings on Windows [v3]

[Jorn Vernee]

On Wed, 20 Jul 2022 15:13:05 GMT, Andrew Haley <aph at openjdk.org> wrote:

> > I think having `PRAGMA_ALLOW_LOSSY_CONVERSIONS` in the file also sends a much clearer message that: warnings in this file have not been looked at/fixed yet, which I don't think `checked_cast` does.
> 
> It kinda would, because such casts would have to be considered. But OK.

What I mean is that `checked_cast` can also be used intentionally. So, looking at a particular `checked_cast` it might be hard to tell if this use case should still be address/fixed. or if it has already been addressed and the solution was to use `checked_cast`.

> > The approach I've taken preserves the current behavior of the code, but it also allows for fixing these warnings on a per-file basis (besides enabling the warning for the 800 or so files that don't have warnings right now). This seems to me like an easier and safer way to make progress.
> 
> OK, so this is hopefully a temporary fix.

Yes, this is not meant to be a long term solution. Just a way of allowing for more incremental progress, as well as a stop gap for files that are good today.

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PR: https://git.openjdk.org/jdk/pull/9516